              Frequently Asked Questions for FreeBSD 11.X and 12.X

  The FreeBSD Documentation Project

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   Abstract

   This is the Frequently Asked Questions (FAQ) for FreeBSD versions 12.X and
   11.X. Every effort has been made to make this FAQ as informative as
   possible; if you have any suggestions as to how it may be improved, send
   them to the FreeBSD documentation project mailing list.

   The latest version of this document is always available from the FreeBSD
   website. It may also be downloaded as one large HTML file with HTTP or as
   a variety of other formats from the FreeBSD FTP server.

   [ Split HTML / Single HTML ]

     ----------------------------------------------------------------------

   Table of Contents

   1. Introduction

   2. Documentation and Support

   3. Installation

   4. Hardware Compatibility

                4.1. General

                4.2. Architectures and Processors

                4.3. Peripherals

                4.4. Keyboards and Mice

                4.5. Other Hardware

   5. Troubleshooting

   6. User Applications

   7. Kernel Configuration

   8. Disks, File Systems, and Boot Loaders

   9. ZFS

   10. System Administration

   11. The X Window System and Virtual Consoles

   12. Networking

   13. Security

   14. Serial Communications

   15. Miscellaneous Questions

   16. The FreeBSD Funnies

   17. Advanced Topics

   18. Acknowledgments

                            Chapter 1. Introduction

   1.1. What is FreeBSD?

   1.2. What is the goal of the FreeBSD Project?

   1.3. Does the FreeBSD license have any restrictions?

   1.4. Can FreeBSD replace my current operating system?

   1.5. Why is it called FreeBSD?

   1.6. What are the differences between FreeBSD and NetBSD, OpenBSD, and
   other open source BSD operating systems?

   1.7. What is the latest version of FreeBSD?

   1.8. What is FreeBSD-CURRENT?

   1.9. What is the FreeBSD-STABLE concept?

   1.10. When are FreeBSD releases made?

   1.11. When are FreeBSD snapshots made?

   1.12. Who is responsible for FreeBSD?

   1.13. Where can I get FreeBSD?

   1.14. How do I access the Problem Report database?

   1.1.  What is FreeBSD?                                                     
         FreeBSD is a modern operating system for desktops, laptops, servers, 
         and embedded systems with support for a large number of platforms.   
                                                                              
         It is based on U.C. Berkeley's "4.4BSD-Lite" release, with some      
         "4.4BSD-Lite2" enhancements. It is also based indirectly on William  
         Jolitz's port of U.C. Berkeley's "Net/2" to the i386(TM), known as   
         "386BSD", though very little of the 386BSD code remains.             
                                                                              
         FreeBSD is used by companies, Internet Service Providers,            
         researchers, computer professionals, students and home users all     
         over the world in their work, education and recreation.              
                                                                              
         For more detailed information on FreeBSD, refer to the FreeBSD       
         Handbook.                                                            
   1.2.  What is the goal of the FreeBSD Project?                             
         The goal of the FreeBSD Project is to provide a stable and fast      
         general purpose operating system that may be used for any purpose    
         without strings attached.                                            
   1.3.  Does the FreeBSD license have any restrictions?                      
         Yes. Those restrictions do not control how the code is used, but how 
         to treat the FreeBSD Project itself. The license itself is available 
         at license and can be summarized like this:                          
                                                                              
           * Do not claim that you wrote this.                                
                                                                              
           * Do not sue us if it breaks.                                      
                                                                              
           * Do not remove or modify the license.                             
                                                                              
         Many of us have a significant investment in the project and would    
         certainly not mind a little financial compensation now and then, but 
         we definitely do not insist on it. We believe that our first and     
         foremost "mission" is to provide code to any and all comers, and for 
         whatever purpose, so that the code gets the widest possible use and  
         provides the widest possible benefit. This, we believe, is one of    
         the most fundamental goals of Free Software and one that we          
         enthusiastically support.                                            
                                                                              
         Code in our source tree which falls under the GNU General Public     
         License (GPL) or GNU Library General Public License (LGPL) comes     
         with slightly more strings attached, though at least on the side of  
         enforced access rather than the usual opposite. Due to the           
         additional complexities that can evolve in the commercial use of GPL 
         software, we do, however, endeavor to replace such software with     
         submissions under the more relaxed FreeBSD license whenever          
         possible.                                                            
   1.4.  Can FreeBSD replace my current operating system?                     
         For most people, yes. But this question is not quite that            
         cut-and-dried.                                                       
                                                                              
         Most people do not actually use an operating system. They use        
         applications. The applications are what really use the operating     
         system. FreeBSD is designed to provide a robust and full-featured    
         environment for applications. It supports a wide variety of web      
         browsers, office suites, email readers, graphics programs,           
         programming environments, network servers, and much more. Most of    
         these applications can be managed through the Ports Collection.      
                                                                              
         If an application is only available on one operating system, that    
         operating system cannot just be replaced. Chances are, there is a    
         very similar application on FreeBSD, however. As a solid office or   
         Internet server or a reliable workstation, FreeBSD will almost       
         certainly do everything you need. Many computer users across the     
         world, including both novices and experienced UNIX(R)                
         administrators, use FreeBSD as their only desktop operating system.  
                                                                              
         Users migrating to FreeBSD from another UNIX(R)-like environment     
         will find FreeBSD to be similar. Windows(R) and Mac OS(R) users may  
         be interested in instead using GhostBSD, MidnightBSD or NomadBSD     
         three FreeBSD-based desktop distributions. Non-UNIX(R) users should  
         expect to invest some additional time learning the UNIX(R) way of    
         doing things. This FAQ and the FreeBSD Handbook are excellent places 
         to start.                                                            
   1.5.  Why is it called FreeBSD?                                            
           * It may be used free of charge, even by commercial users.         
                                                                              
           * Full source for the operating system is freely available, and    
             the minimum possible restrictions have been placed upon its use, 
             distribution and incorporation into other work (commercial or    
             non-commercial).                                                 
                                                                              
           * Anyone who has an improvement or bug fix is free to submit their 
             code and have it added to the source tree (subject to one or two 
             obvious provisions).                                             
                                                                              
         It is worth pointing out that the word "free" is being used in two   
         ways here: one meaning "at no cost" and the other meaning "do        
         whatever you like". Apart from one or two things you cannot do with  
         the FreeBSD code, for example pretending you wrote it, you can       
         really do whatever you like with it.                                 
   1.6.  What are the differences between FreeBSD and NetBSD, OpenBSD, and    
         other open source BSD operating systems?                             
         James Howard wrote a good explanation of the history and differences 
         between the various projects, called The BSD Family Tree which goes  
         a fair way to answering this question. Some of the information is    
         out of date, but the history portion in particular remains accurate. 
                                                                              
         Most of the BSDs share patches and code, even today. All of the BSDs 
         have common ancestry.                                                
                                                                              
         The design goals of FreeBSD are described in Q: 1.2, above. The      
         design goals of the other most popular BSDs may be summarized as     
         follows:                                                             
                                                                              
           * OpenBSD aims for operating system security above all else. The   
             OpenBSD team wrote ssh(1) and pf(4), which have both been ported 
             to FreeBSD.                                                      
                                                                              
           * NetBSD aims to be easily ported to other hardware platforms.     
                                                                              
           * DragonFly BSD is a fork of FreeBSD 4.8 that has since developed  
             many interesting features of its own, including the HAMMER file  
             system and support for user-mode "vkernels".                     
   1.7.  What is the latest version of FreeBSD?                               
         At any point in the development of FreeBSD, there can be multiple    
         parallel branches. 12.X releases are made from the 12-STABLE branch, 
         and 11.X releases are made from the 11-STABLE branch.                
                                                                              
         Up until the release of 12.0, the 11.X series was the one known as   
         -STABLE. However, as of 13.X, the 11.X branch will be designated for 
         an "extended support" status and receive only fixes for major        
         problems, such as security-related fixes.                            
                                                                              
         Releases are made every few months. While many people stay more      
         up-to-date with the FreeBSD sources (see the questions on            
         FreeBSD-CURRENT and FreeBSD-STABLE) than that, doing so is more of a 
         commitment, as the sources are a moving target.                      
                                                                              
         More information on FreeBSD releases can be found on the Release     
         Engineering page and in release(7).                                  
   1.8.  What is FreeBSD-CURRENT?                                             
         FreeBSD-CURRENT is the development version of the operating system,  
         which will in due course become the new FreeBSD-STABLE branch. As    
         such, it is really only of interest to developers working on the     
         system and die-hard hobbyists. See the relevant section in the       
         Handbook for details on running -CURRENT.                            
                                                                              
         Users not familiar with FreeBSD should not use FreeBSD-CURRENT. This 
         branch sometimes evolves quite quickly and due to mistake can be     
         un-buildable at times. People that use FreeBSD-CURRENT are expected  
         to be able to analyze, debug, and report problems.                   
   1.9.  What is the FreeBSD-STABLE concept?                                  
         FreeBSD-STABLE is the development branch from which major releases   
         are made. Changes go into this branch at a slower pace and with the  
         general assumption that they have first been tested in               
         FreeBSD-CURRENT. However, at any given time, the sources for         
         FreeBSD-STABLE may or may not be suitable for general use, as it may 
         uncover bugs and corner cases that were not yet found in             
         FreeBSD-CURRENT. Users who do not have the resources to perform      
         testing should instead run the most recent release of FreeBSD.       
         FreeBSD-CURRENT, on the other hand, has been one unbroken line since 
         2.0 was released.                                                    
                                                                              
         For more detailed information on branches see "FreeBSD Release       
         Engineering: Creating the Release Branch", the status of the         
         branches and the upcoming release schedule can be found on the       
         Release Engineering Information page.                                
                                                                              
         Version 12.1 is the latest release from the 12-STABLE branch; it was 
         released in November 2019. Version 11.3 is the latest release from   
         the 11-STABLE branch; it was released in July 2019.                  
   1.10. When are FreeBSD releases made?                                      
         The Release Engineering Team <re@FreeBSD.org> releases a new major   
         version of FreeBSD about every 18 months and a new minor version     
         about every 8 months, on average. Release dates are announced well   
         in advance, so that the people working on the system know when their 
         projects need to be finished and tested. A testing period precedes   
         each release, to ensure that the addition of new features does not   
         compromise the stability of the release. Many users regard this      
         caution as one of the best things about FreeBSD, even though waiting 
         for all the latest goodies to reach -STABLE can be a little          
         frustrating.                                                         
                                                                              
         More information on the release engineering process (including a     
         schedule of upcoming releases) can be found on the release           
         engineering pages on the FreeBSD Web site.                           
                                                                              
         For people who need or want a little more excitement, binary         
         snapshots are made weekly as discussed above.                        
   1.11. When are FreeBSD snapshots made?                                     
         FreeBSD snapshot releases are made based on the current state of the 
         -CURRENT and -STABLE branches. The goals behind each snapshot        
         release are:                                                         
                                                                              
           * To test the latest version of the installation software.         
                                                                              
           * To give people who would like to run -CURRENT or -STABLE but who 
             do not have the time or bandwidth to follow it on a day-to-day   
             basis an easy way of bootstrapping it onto their systems.        
                                                                              
           * To preserve a fixed reference point for the code in question,    
             just in case we break something really badly later. (Although    
             Subversion normally prevents anything horrible like this         
             happening.)                                                      
                                                                              
           * To ensure that all new features and fixes in need of testing     
             have the greatest possible number of potential testers.          
                                                                              
         No claims are made that any -CURRENT snapshot can be considered      
         "production quality" for any purpose. If a stable and fully tested   
         system is needed, stick to full releases.                            
                                                                              
         Snapshot releases are directly available from snapshot.              
                                                                              
         Official snapshots are generated on a regular basis for all actively 
         developed branches.                                                  
   1.12. Who is responsible for FreeBSD?                                      
         The key decisions concerning the FreeBSD project, such as the        
         overall direction of the project and who is allowed to add code to   
         the source tree, are made by a core team of 9 people. There is a     
         much larger team of more than 350 committers who are authorized to   
         make changes directly to the FreeBSD source tree.                    
                                                                              
         However, most non-trivial changes are discussed in advance in the    
         mailing lists, and there are no restrictions on who may take part in 
         the discussion.                                                      
   1.13. Where can I get FreeBSD?                                             
         Every significant release of FreeBSD is available via anonymous FTP  
         from the FreeBSD FTP site:                                           
                                                                              
           * The latest 12-STABLE release, 12.1-RELEASE can be found in the   
             12.1-RELEASE directory.                                          
                                                                              
           * Snapshot releases are made monthly for the -CURRENT and -STABLE  
             branch, these being of service purely to bleeding-edge testers   
             and developers.                                                  
                                                                              
           * The latest 11-STABLE release, 11.3-RELEASE can be found in the   
             11.3-RELEASE directory.                                          
                                                                              
         Information about obtaining FreeBSD on CD, DVD, and other media can  
         be found in the Handbook.                                            
   1.14. How do I access the Problem Report database?                         
         The Problem Report database of all user change requests may be       
         queried by using our web-based PR query interface.                   
                                                                              
         The web-based problem report submission interface can be used to     
         submit problem reports through a web browser.                        
                                                                              
         Before submitting a problem report, read Writing FreeBSD Problem     
         Reports, an article on how to write good problem reports.            

                      Chapter 2. Documentation and Support

   2.1. What good books are there about FreeBSD?

   2.2. Is the documentation available in other formats, such as plain text
   (ASCII), or PDF?

   2.3. Where do I find info on the FreeBSD mailing lists? What FreeBSD news
   groups are available?

   2.4. Are there FreeBSD IRC (Internet Relay Chat) channels?

   2.5. Are there any web based forums to discuss FreeBSD?

   2.6. Where can I get commercial FreeBSD training and support?

2.1. What good books are there about FreeBSD?                                                       
     The project produces a wide range of documentation, available online from this link:           
     https://www.FreeBSD.org/docs.html.                                                             
2.2. Is the documentation available in other formats, such as plain text (ASCII), or PDF?           
     Yes. The documentation is available in a number of different formats and compression schemes   
     on the FreeBSD FTP site, in the /ftp/doc/ directory.                                           
                                                                                                    
     The documentation is categorized in a number of different ways. These include:                 
                                                                                                    
       * The document's name, such as faq, or handbook.                                             
                                                                                                    
       * The document's language and encoding. These are based on the locale names found under      
         /usr/share/locale on a FreeBSD system. The current languages and encodings are as follows: 
                                                                                                    
                      Name                                        Meaning                           
         en_US.ISO8859-1                 English (United States)                                    
         bn_BD.ISO10646-1                Bengali or Bangla (Bangladesh)                             
         da_DK.ISO8859-1                 Danish (Denmark)                                           
         de_DE.ISO8859-1                 German (Germany)                                           
         el_GR.ISO8859-7                 Greek (Greece)                                             
         es_ES.ISO8859-1                 Spanish (Spain)                                            
         fr_FR.ISO8859-1                 French (France)                                            
         hu_HU.ISO8859-2                 Hungarian (Hungary)                                        
         it_IT.ISO8859-15                Italian (Italy)                                            
         ja_JP.eucJP                     Japanese (Japan, EUC encoding)                             
         ko_KR.UTF-8                     Korean (Korea, UTF-8 encoding)                             
         mn_MN.UTF-8                     Mongolian (Mongolia, UTF-8 encoding)                       
         nl_NL.ISO8859-1                 Dutch (Netherlands)                                        
         pl_PL.ISO8859-2                 Polish (Poland)                                            
         pt_BR.ISO8859-1                 Portuguese (Brazil)                                        
         ru_RU.KOI8-R                    Russian (Russia, KOI8-R encoding)                          
         tr_TR.ISO8859-9                 Turkish (Turkey)                                           
         zh_CN.UTF-8                     Simplified Chinese (China, UTF-8 encoding)                 
         zh_TW.UTF-8                     Traditional Chinese (Taiwan, UTF-8 encoding)               
                                                                                                    
       Note:                                                                                        
                                                                                                    
         Some documents may not be available in all languages.                                      
                                                                                                    
       * The document's format. We produce the documentation in a number of different output        
         formats. Each format has its own advantages and disadvantages. Some formats are better     
         suited for online reading, while others are meant to be aesthetically pleasing when        
         printed on paper. Having the documentation available in any of these formats ensures that  
         our readers will be able to read the parts they are interested in, either on their         
         monitor, or on paper after printing the documents. The currently available formats are:    
                                                                                                    
                  Format                                       Meaning                              
         html-split                A collection of small, linked, HTML files.                       
         html                      One large HTML file containing the entire document               
         pdf                       Adobe's Portable Document Format                                 
         txt                       Plain text                                                       
                                                                                                    
       * The compression and packaging scheme.                                                      
                                                                                                    
           1. Where the format is html-split, the files are bundled up using tar(1). The resulting  
              .tar is then compressed using the compression schemes detailed in the next point.     
                                                                                                    
           2. All the other formats generate one file. For example, article.pdf, book.html, and so  
              on.                                                                                   
                                                                                                    
              These files are then compressed using either the zip or bz2 compression schemes.      
              tar(1) can be used to uncompress these files.                                         
                                                                                                    
              So the PDF version of the Handbook, compressed using bzip2 will be stored in a file   
              called book.pdf.bz2 in the handbook/ directory.                                       
                                                                                                    
     After choosing the format and compression mechanism, download the compressed files, uncompress 
     them, and then copy the appropriate documents into place.                                      
                                                                                                    
     For example, the split HTML version of the FAQ, compressed using bzip2(1), can be found in     
     doc/en_US.ISO8859-1/books/faq/book.html-split.tar.bz2 To download and uncompress that file,    
     type:                                                                                          
                                                                                                    
     # fetch https://download.freebsd.org/ftp/doc/en_US.ISO8859-1/books/faq/book.html-split.tar.bz2 
     # tar xvf book.html-split.tar.bz2                                                              
                                                                                                    
     If the file is compressed, tar will automatically detect the appropriate format and decompress 
     it correctly, resulting in a collection of .html files. The main one is called index.html,     
     which will contain the table of contents, introductory material, and links to the other parts  
     of the document.                                                                               
2.3. Where do I find info on the FreeBSD mailing lists? What FreeBSD news groups are available?     
     Refer to the Handbook entry on mailing-lists and the Handbook entry on newsgroups.             
2.4. Are there FreeBSD IRC (Internet Relay Chat) channels?                                          
     Yes, most major IRC networks host a FreeBSD chat channel:                                      
                                                                                                    
       * Channel #FreeBSDhelp on EFNet is a channel dedicated to helping FreeBSD users.             
                                                                                                    
       * Channel #FreeBSD on Freenode is a general help channel with many users at any time. The    
         conversations have been known to run off-topic for a while, but priority is given to users 
         with FreeBSD questions. Other users can help with the basics, referring to the Handbook    
         whenever possible and providing links for learning more about a particular topic. This is  
         primarily an English speaking channel, though it does have users from all over the world.  
         Non-native English speakers should try to ask the question in English first and then       
         relocate to ##freebsd-lang as appropriate.                                                 
                                                                                                    
       * Channel #FreeBSD on DALNET is available at irc.dal.net in the US and irc.eu.dal.net in     
         Europe.                                                                                    
                                                                                                    
       * Channel #FreeBSD on UNDERNET is available at us.undernet.org in the US and eu.undernet.org 
         in Europe. Since it is a help channel, be prepared to read the documents you are referred  
         to.                                                                                        
                                                                                                    
       * Channel #FreeBSD on RUSNET is a Russian language channel dedicated to helping FreeBSD      
         users. This is also a good place for non-technical discussions.                            
                                                                                                    
       * Channel #bsdchat on Freenode is a Traditional Chinese (UTF-8 encoding) language channel    
         dedicated to helping FreeBSD users. This is also a good place for non-technical            
         discussions.                                                                               
                                                                                                    
     The FreeBSD wiki has a good list of IRC channels.                                              
                                                                                                    
     Each of these channels are distinct and are not connected to each other. Since their chat      
     styles differ, try each to find one suited to your chat style.                                 
2.5. Are there any web based forums to discuss FreeBSD?                                             
     The official FreeBSD forums are located at https://forums.FreeBSD.org/.                        
2.6. Where can I get commercial FreeBSD training and support?                                       
     iXsystems, Inc., parent company of the FreeBSD Mall, provides commercial FreeBSD and TrueOS    
     software support, in addition to FreeBSD development and tuning solutions.                     
                                                                                                    
     BSD Certification Group, Inc. provides system administration certifications for DragonFly BSD, 
     FreeBSD, NetBSD, and OpenBSD. Refer to their site for more information.                        
                                                                                                    
     Any other organizations providing training and support should contact the Project to be listed 
     here.                                                                                          

                            Chapter 3. Installation

   Nik Clayton

   3.1. Which platform should I download? I have a 64 bit capable Intel(R)
   CPU, but I only see amd64.

   3.2. Which file do I download to get FreeBSD?

   3.3. What do I do if the install image does not boot?

   3.4. Where are the instructions for installing FreeBSD?

   3.5. How can I make my own custom release or install disk?

   3.6. Can Windows(R) co-exist with FreeBSD? (x86-specific)

   3.7. Another operating system destroyed my Boot Manager. How do I get it
   back? (x86-specific)

   3.8. Do I need to install the source?

   3.9. Do I need to build a kernel?

   3.10. Should I use DES, Blowfish, or MD5 passwords and how do I specify
   which form my users receive?

   3.11. What are the limits for FFS file systems?

   3.12. Why do I get an error message, readin failed after compiling and
   booting a new kernel?

   3.13. Is there a tool to perform post-installation configuration tasks?

   3.1.  Which platform should I download? I have a 64 bit capable Intel(R)   
         CPU, but I only see amd64.                                           
         amd64 is the term FreeBSD uses for 64-bit compatible x86             
         architectures (also known as "x86-64" or "x64"). Most modern         
         computers should use amd64. Older hardware should use i386. When     
         installing on a non-x86-compatible architecture, select the platform 
         which best matches the hardware.                                     
   3.2.  Which file do I download to get FreeBSD?                             
         On the Getting FreeBSD page, select [iso] next to the architecture   
         that matches the hardware.                                           
                                                                              
         Any of the following can be used:                                    
                                                                              
             file                           description                       
         disc1.iso    Contains enough to install FreeBSD and a minimal set of 
                      packages.                                               
         dvd1.iso     Similar to disc1.iso but with additional packages.      
         memstick.img A bootable image sufficient for writing to a USB stick. 
         bootonly.iso A minimal image that requires network access during     
                      installation to completely install FreeBSD.             
                                                                              
         Full instructions on this procedure and a little bit more about      
         installation issues in general can be found in the Handbook entry on 
         installing FreeBSD.                                                  
   3.3.  What do I do if the install image does not boot?                     
         This can be caused by not downloading the image in binary mode when  
         using FTP.                                                           
                                                                              
         Some FTP clients default their transfer mode to ascii and attempt to 
         change any end-of-line characters received to match the conventions  
         used by the client's system. This will almost invariably corrupt the 
         boot image. Check the SHA-256 checksum of the downloaded boot image: 
         if it is not exactly that on the server, then the download process   
         is suspect.                                                          
                                                                              
         When using a command line FTP client, type binary at the FTP command 
         prompt after getting connected to the server and before starting the 
         download of the image.                                               
   3.4.  Where are the instructions for installing FreeBSD?                   
         Installation instructions can be found at Handbook entry on          
         installing FreeBSD.                                                  
   3.5.  How can I make my own custom release or install disk?                
         Customized FreeBSD installation media can be created by building a   
         custom release. Follow the instructions in the Release Engineering   
         article.                                                             
   3.6.  Can Windows(R) co-exist with FreeBSD? (x86-specific)                 
         If Windows(R) is installed first, then yes. FreeBSD's boot manager   
         will then manage to boot Windows(R) and FreeBSD. If Windows(R) is    
         installed afterwards, it will overwrite the boot manager. If that    
         happens, see the next section.                                       
   3.7.  Another operating system destroyed my Boot Manager. How do I get it  
         back? (x86-specific)                                                 
         This depends upon the boot manager. The FreeBSD boot selection menu  
         can be reinstalled using boot0cfg(8). For example, to restore the    
         boot menu onto the disk ada0:                                        
                                                                              
         # boot0cfg -B ada0                                                   
                                                                              
         The non-interactive MBR bootloader can be installed using gpart(8):  
                                                                              
         # gpart bootcode -b /boot/mbr ada0                                   
                                                                              
         For more complex situations, including GPT disks, see gpart(8).      
   3.8.  Do I need to install the source?                                     
         In general, no. There is nothing in the base system which requires   
         the presence of the source to operate. Some ports, like              
         sysutils/lsof, will not build unless the source is installed. In     
         particular, if the port builds a kernel module or directly operates  
         on kernel structures, the source must be installed.                  
   3.9.  Do I need to build a kernel?                                         
         Usually not. The supplied GENERIC kernel contains the drivers an     
         ordinary computer will need. freebsd-update(8), the FreeBSD binary   
         upgrade tool, cannot upgrade custom kernels, another reason to stick 
         with the GENERIC kernel when possible. For computers with very       
         limited RAM, such as embedded systems, it may be worthwhile to build 
         a smaller custom kernel containing just the required drivers.        
   3.10. Should I use DES, Blowfish, or MD5 passwords and how do I specify    
         which form my users receive?                                         
         FreeBSD uses SHA512 by default. DES passwords are still available    
         for backwards compatibility with operating systems that still use    
         the less secure password format. FreeBSD also supports the Blowfish  
         and MD5 password formats. Which password format to use for new       
         passwords is controlled by the passwd_format login capability in     
         /etc/login.conf, which takes values of des, blf (if these are        
         available) or md5. See the login.conf(5) manual page for more        
         information about login capabilities.                                
   3.11. What are the limits for FFS file systems?                            
         For FFS file systems, the largest file system is practically limited 
         by the amount of memory required to fsck(8) the file system. fsck(8) 
         requires one bit per fragment, which with the default fragment size  
         of 4 KB equates to 32 MB of memory per TB of disk. This does mean    
         that on architectures which limit userland processes to 2 GB (e.g.,  
         i386(TM)), the maximum fsck(8)'able filesystem is ~60 TB.            
                                                                              
         If there was not a fsck(8) memory limit the maximum filesystem size  
         would be 2 ^ 64 (blocks) * 32 KB => 16 Exa * 32 KB => 512            
         ZettaBytes.                                                          
                                                                              
         The maximum size of a single FFS file is approximately 2 PB with the 
         default block size of 32 KB. Each 32 KB block can point to 4096      
         blocks. With triple indirect blocks, the calculation is 32 KB * 12 + 
         32 KB * 4096 + 32 KB * 4096^2 + 32 KB * 4096^3. Increasing the block 
         size to 64 KB will increase the max file size by a factor of 16.     
   3.12. Why do I get an error message, readin failed after compiling and     
         booting a new kernel?                                                
         The world and kernel are out of sync. This is not supported. Be sure 
         to use make buildworld and make buildkernel to update the kernel.    
                                                                              
         Boot the system by specifying the kernel directly at the second      
         stage, pressing any key when the | shows up before loader is         
         started.                                                             
   3.13. Is there a tool to perform post-installation configuration tasks?    
         Yes. bsdconfig provides a nice interface to configure FreeBSD        
         post-installation.                                                   

                       Chapter 4. Hardware Compatibility

   Table of Contents

   4.1. General

   4.2. Architectures and Processors

   4.3. Peripherals

   4.4. Keyboards and Mice

   4.5. Other Hardware

4.1. General

   4.1.1. I want to get a piece of hardware for my FreeBSD system. Which
   model/brand/type is best?

   4.1.2. What are the limits for memory?

   4.1.3. Why does FreeBSD report less than 4 GB memory when installed on an
   i386(TM) machine?

   4.1.1. I want to get a piece of hardware for my FreeBSD system. Which      
          model/brand/type is best?                                           
          This is discussed continually on the FreeBSD mailing lists but is   
          to be expected since hardware changes so quickly. Read through the  
          Hardware Notes for FreeBSD 12.1 or 11.3 and search the mailing list 
          archives before asking about the latest and greatest hardware.      
          Chances are a discussion about that type of hardware took place     
          just last week.                                                     
                                                                              
          Before purchasing a laptop, check the archives for FreeBSD general  
          questions mailing list, or possibly a specific mailing list for a   
          particular hardware type.                                           
   4.1.2. What are the limits for memory?                                     
          FreeBSD as an operating system generally supports as much physical  
          memory (RAM) as the platform it is running on does. Keep in mind    
          that different platforms have different limits for memory; for      
          example i386(TM) without PAE supports at most 4 GB of memory (and   
          usually less than that because of PCI address space) and i386(TM)   
          with PAE supports at most 64 GB memory. As of FreeBSD 10, AMD64     
          platforms support up to 4 TB of physical memory.                    
   4.1.3. Why does FreeBSD report less than 4 GB memory when installed on an  
          i386(TM) machine?                                                   
          The total address space on i386(TM) machines is 32-bit, meaning     
          that at most 4 GB of memory is addressable (can be accessed).       
          Furthermore, some addresses in this range are reserved by hardware  
          for different purposes, for example for using and controlling PCI   
          devices, for accessing video memory, and so on. Therefore, the      
          total amount of memory usable by the operating system for its       
          kernel and applications is limited to significantly less than 4 GB. 
          Usually, 3.2 GB to 3.7 GB is the maximum usable physical memory in  
          this configuration.                                                 
                                                                              
          To access more than 3.2 GB to 3.7 GB of installed memory (meaning   
          up to 4 GB but also more than 4 GB), a special tweak called PAE     
          must be used. PAE stands for Physical Address Extension and is a    
          way for 32-bit x86 CPUs to address more than 4 GB of memory. It     
          remaps the memory that would otherwise be overlaid by address       
          reservations for hardware devices above the 4 GB range and uses it  
          as additional physical memory (see pae(4)). Using PAE has some      
          drawbacks; this mode of memory access is a little bit slower than   
          the normal (without PAE) mode and loadable modules (see kld(4)) are 
          not supported. This means all drivers must be compiled into the     
          kernel.                                                             
                                                                              
          The most common way to enable PAE is to build a new kernel with the 
          special ready-provided kernel configuration file called PAE, which  
          is already configured to build a safe kernel. Note that some        
          entries in this kernel configuration file are too conservative and  
          some drivers marked as unready to be used with PAE are actually     
          usable. A rule of thumb is that if the driver is usable on 64-bit   
          architectures (like AMD64), it is also usable with PAE. When        
          creating a custom kernel configuration file, PAE can be enabled by  
          adding the following line:                                          
                                                                              
          options       PAE                                                   
                                                                              
          PAE is not much used nowadays because most new x86 hardware also    
          supports running in 64-bit mode, known as AMD64 or Intel(R) 64. It  
          has a much larger address space and does not need such tweaks.      
          FreeBSD supports AMD64 and it is recommended that this version of   
          FreeBSD be used instead of the i386(TM) version if 4 GB or more     
          memory is required.                                                 

4.2. Architectures and Processors

   4.2.1. Does FreeBSD support architectures other than the x86?

   4.2.2. Does FreeBSD support Symmetric Multiprocessing (SMP)?

   4.2.3. What is microcode? How do I install Intel(R) CPU microcode updates?

   4.2.1. Does FreeBSD support architectures other than the x86?              
          Yes. FreeBSD divides support into multiple tiers. Tier 1            
          architectures, such as i386 or amd64; are fully supported. Tiers 2  
          and 3 are supported on a best-effort basis. A full explanation of   
          the tier system is available in the Committer's Guide.              
                                                                              
          A complete list of supported architectures can be found on the      
          platforms page.                                                     
   4.2.2. Does FreeBSD support Symmetric Multiprocessing (SMP)?               
          FreeBSD supports symmetric multi-processor (SMP) on all             
          non-embedded platforms (e.g, i386, amd64, etc.). SMP is also        
          supported in arm and MIPS kernels, although some CPUs may not       
          support this. FreeBSD's SMP implementation uses fine-grained        
          locking, and performance scales nearly linearly with number of      
          CPUs.                                                               
                                                                              
          smp(4) has more details.                                            
   4.2.3. What is microcode? How do I install Intel(R) CPU microcode updates? 
          Microcode is a method of programmatically implementing hardware     
          level instructions. This allows for CPU bugs to be fixed without    
          replacing the on board chip.                                        
                                                                              
          Install sysutils/devcpu-data, then add:                             
                                                                              
          microcode_update_enable="YES"                                       
                                                                              
          to /etc/rc.conf                                                     

4.3. Peripherals

   4.3.1. What kind of peripherals does FreeBSD support?

   4.3.1. What kind of peripherals does FreeBSD support?                      
          See the complete list in the Hardware Notes for FreeBSD 12.1 or     
          11.3.                                                               

4.4. Keyboards and Mice

   4.4.1. Is it possible to use a mouse outside the X Window system?

   4.4.2. How do I cut and paste text with a mouse in the text console?

   4.4.3. My mouse has a fancy wheel and buttons. Can I use them in FreeBSD?

   4.4.4. How do I use my delete key in sh and csh?

   4.4.1. Is it possible to use a mouse outside the X Window system?          
          The default console driver, vt(4), provides the ability to use a    
          mouse pointer in text consoles to cut & paste text. Run the mouse   
          daemon, moused(8), and turn on the mouse pointer in the virtual     
          console:                                                            
                                                                              
          # moused -p /dev/xxxx -t yyyy                                       
          # vidcontrol -m on                                                  
                                                                              
          Where xxxx is the mouse device name and yyyy is a protocol type for 
          the mouse. The mouse daemon can automatically determine the         
          protocol type of most mice, except old serial mice. Specify the     
          auto protocol to invoke automatic detection. If automatic detection 
          does not work, see the moused(8) manual page for a list of          
          supported protocol types.                                           
                                                                              
          For a PS/2 mouse, add moused_enable="YES" to /etc/rc.conf to start  
          the mouse daemon at boot time. Additionally, to use the mouse       
          daemon on all virtual terminals instead of just the console, add    
          allscreens_flags="-m on" to /etc/rc.conf.                           
                                                                              
          When the mouse daemon is running, access to the mouse must be       
          coordinated between the mouse daemon and other programs such as X   
          Windows. Refer to the FAQ Why does my mouse not work with X? for    
          more details on this issue.                                         
   4.4.2. How do I cut and paste text with a mouse in the text console?       
          It is not possible to remove data using the mouse. However, it is   
          possible to copy and paste. Once the mouse daemon is running as     
          described in the previous question, hold down button 1 (left        
          button) and move the mouse to select a region of text. Then, press  
          button 2 (middle button) to paste it at the text cursor. Pressing   
          button 3 (right button) will "extend" the selected region of text.  
                                                                              
          If the mouse does not have a middle button, it is possible to       
          emulate one or remap buttons using mouse daemon options. See the    
          moused(8) manual page for details.                                  
   4.4.3. My mouse has a fancy wheel and buttons. Can I use them in FreeBSD?  
          The answer is, unfortunately, "It depends". These mice with         
          additional features require specialized driver in most cases.       
          Unless the mouse device driver or the user program has specific     
          support for the mouse, it will act just like a standard two, or     
          three button mouse.                                                 
                                                                              
          For the possible usage of wheels in the X Window environment, refer 
          to that section.                                                    
   4.4.4. How do I use my delete key in sh and csh?                           
          For the Bourne Shell, add the following lines to ~/.shrc. See sh(1) 
          and editrc(5).                                                      
                                                                              
          bind ^[[3~ ed-delete-next-char # for xterm                          
                                                                              
          For the C Shell, add the following lines to ~/.cshrc. See csh(1).   
                                                                              
          bindkey ^[[3~ delete-char # for xterm                               

4.5. Other Hardware

   4.5.1. Workarounds for no sound from my pcm(4) sound card?

   4.5.2. Does FreeBSD support power management on my laptop?

   4.5.1. Workarounds for no sound from my pcm(4) sound card?                 
          Some sound cards set their output volume to 0 at every boot. Run    
          the following command every time the machine boots:                 
                                                                              
          # mixer pcm 100 vol 100 cd 100                                      
   4.5.2. Does FreeBSD support power management on my laptop?                 
          FreeBSD supports the ACPI features found in modern hardware.        
          Further information can be found in acpi(4).                        

                           Chapter 5. Troubleshooting

   5.1. Why is FreeBSD finding the wrong amount of memory on i386(TM)
   hardware?

   5.2. Why do my programs occasionally die with Signal 11 errors?

   5.3. My system crashes with either Fatal trap 12: page fault in kernel
   mode, or panic:, and spits out a bunch of information. What should I do?

   5.4. What is the meaning of the error maxproc limit exceeded by uid %i,
   please see tuning(7) and login.conf(5)?

   5.5. Why do full screen applications on remote machines misbehave?

   5.6. Why does it take so long to connect to my computer via ssh or telnet?

   5.7. Why does file: table is full show up repeatedly in dmesg(8)?

   5.8. Why does the clock on my computer keep incorrect time?

   5.9. What does the error swap_pager: indefinite wait buffer: mean?

   5.10. What is a lock order reversal?

   5.11. What does Called ... with the following non-sleepable locks held
   mean?

   5.12. Why does buildworld/installworld die with the message touch: not
   found?

   5.1.  Why is FreeBSD finding the wrong amount of memory on i386(TM)        
         hardware?                                                            
         The most likely reason is the difference between physical memory     
         addresses and virtual addresses.                                     
                                                                              
         The convention for most PC hardware is to use the memory area        
         between 3.5 GB and 4 GB for a special purpose (usually for PCI).     
         This address space is used to access PCI hardware. As a result real, 
         physical memory cannot be accessed by that address space.            
                                                                              
         What happens to the memory that should appear in that location is    
         hardware dependent. Unfortunately, some hardware does nothing and    
         the ability to use that last 500 MB of RAM is entirely lost.         
                                                                              
         Luckily, most hardware remaps the memory to a higher location so     
         that it can still be used. However, this can cause some confusion    
         when watching the boot messages.                                     
                                                                              
         On a 32-bit version of FreeBSD, the memory appears lost, since it    
         will be remapped above 4 GB, which a 32-bit kernel is unable to      
         access. In this case, the solution is to build a PAE enabled kernel. 
         See the entry on memory limits for more information.                 
                                                                              
         On a 64-bit version of FreeBSD, or when running a PAE-enabled        
         kernel, FreeBSD will correctly detect and remap the memory so it is  
         usable. During boot, however, it may seem as if FreeBSD is detecting 
         more memory than the system really has, due to the described         
         remapping. This is normal and the available memory will be corrected 
         as the boot process completes.                                       
   5.2.  Why do my programs occasionally die with Signal 11 errors?           
         Signal 11 errors are caused when a process has attempted to access   
         memory which the operating system has not granted it access to. If   
         something like this is happening at seemingly random intervals,      
         start investigating the cause.                                       
                                                                              
         These problems can usually be attributed to either:                  
                                                                              
          1. If the problem is occurring only in a specific custom            
             application, it is probably a bug in the code.                   
                                                                              
          2. If it is a problem with part of the base FreeBSD system, it may  
             also be buggy code, but more often than not these problems are   
             found and fixed long before us general FAQ readers get to use    
             these bits of code (that is what -CURRENT is for).               
                                                                              
         It is probably not a FreeBSD bug if the problem occurs compiling a   
         program, but the activity that the compiler is carrying out changes  
         each time.                                                           
                                                                              
         For example, if make buildworld fails while trying to compile ls.c   
         into ls.o and, when run again, it fails in the same place, this is a 
         broken build. Try updating source and try again. If the compile      
         fails elsewhere, it is almost certainly due to hardware.             
                                                                              
         In the first case, use a debugger such as gdb(1) to find the point   
         in the program which is attempting to access a bogus address and fix 
         it.                                                                  
                                                                              
         In the second case, verify which piece of hardware is at fault.      
                                                                              
         Common causes of this include:                                       
                                                                              
          1. The hard disks might be overheating: Check that the fans are     
             still working, as the disk and other hardware might be           
             overheating.                                                     
                                                                              
          2. The processor running is overheating: This might be because the  
             processor has been overclocked, or the fan on the processor      
             might have died. In either case, ensure that the hardware is     
             running at what it is specified to run at, at least while trying 
             to solve this problem. If it is not, clock it back to the        
             default settings.)                                               
                                                                              
             Regarding overclocking, it is far cheaper to have a slow system  
             than a fried system that needs replacing! Also the community is  
             not sympathetic to problems on overclocked systems.              
                                                                              
          3. Dodgy memory: if multiple memory SIMMS/DIMMS are installed, pull 
             them all out and try running the machine with each SIMM or DIMM  
             individually to narrow the problem down to either the            
             problematic DIMM/SIMM or perhaps even a combination.             
                                                                              
          4. Over-optimistic motherboard settings: the BIOS settings, and     
             some motherboard jumpers, provide options to set various         
             timings. The defaults are often sufficient, but sometimes        
             setting the wait states on RAM too low, or setting the "RAM      
             Speed: Turbo" option will cause strange behavior. A possible     
             idea is to set to BIOS defaults, after noting the current        
             settings first.                                                  
                                                                              
          5. Unclean or insufficient power to the motherboard. Remove any     
             unused I/O boards, hard disks, or CD-ROMs, or disconnect the     
             power cable from them, to see if the power supply can manage a   
             smaller load. Or try another power supply, preferably one with a 
             little more power. For instance, if the current power supply is  
             rated at 250 Watts, try one rated at 300 Watts.                  
                                                                              
         Read the section on Signal 11 for a further explanation and a        
         discussion on how memory testing software or hardware can still pass 
         faulty memory. There is an extensive FAQ on this at the SIG11        
         problem FAQ.                                                         
                                                                              
         Finally, if none of this has helped, it is possibly a bug in         
         FreeBSD. Follow these instructions to send a problem report.         
   5.3.  My system crashes with either Fatal trap 12: page fault in kernel    
         mode, or panic:, and spits out a bunch of information. What should I 
         do?                                                                  
         The FreeBSD developers are interested in these errors, but need more 
         information than just the error message. Copy the full crash         
         message. Then consult the FAQ section on kernel panics, build a      
         debugging kernel, and get a backtrace. This might sound difficult,   
         but does not require any programming skills. Just follow the         
         instructions.                                                        
   5.4.  What is the meaning of the error maxproc limit exceeded by uid %i,   
         please see tuning(7) and login.conf(5)?                              
         The FreeBSD kernel will only allow a certain number of processes to  
         exist at one time. The number is based on the kern.maxusers          
         sysctl(8) variable. kern.maxusers also affects various other         
         in-kernel limits, such as network buffers. If the machine is heavily 
         loaded, increase kern.maxusers. This will increase these other       
         system limits in addition to the maximum number of processes.        
                                                                              
         To adjust the kern.maxusers value, see the File/Process Limits       
         section of the Handbook. While that section refers to open files,    
         the same limits apply to processes.                                  
                                                                              
         If the machine is lightly loaded but running a very large number of  
         processes, adjust the kern.maxproc tunable by defining it in         
         /boot/loader.conf. The tunable will not get adjusted until the       
         system is rebooted. For more information about tuning tunables, see  
         loader.conf(5). If these processes are being run by a single user,   
         adjust kern.maxprocperuid to be one less than the new kern.maxproc   
         value. It must be at least one less because one system program,      
         init(8), must always be running.                                     
   5.5.  Why do full screen applications on remote machines misbehave?        
         The remote machine may be setting the terminal type to something     
         other than xterm which is required by the FreeBSD console.           
         Alternatively the kernel may have the wrong values for the width and 
         height of the terminal.                                              
                                                                              
         Check the value of the TERM environment variable is xterm. If the    
         remote machine does not support that try vt100.                      
                                                                              
         Run stty -a to check what the kernel thinks the terminal dimensions  
         are. If they are incorrect, they can be changed by running stty rows 
         RR cols CC.                                                          
                                                                              
         Alternatively, if the client machine has x11/xterm installed, then   
         running resize will query the terminal for the correct dimensions    
         and set them.                                                        
   5.6.  Why does it take so long to connect to my computer via ssh or        
         telnet?                                                              
         The symptom: there is a long delay between the time the TCP          
         connection is established and the time when the client software asks 
         for a password (or, in telnet(1)'s case, when a login prompt         
         appears).                                                            
                                                                              
         The problem: more likely than not, the delay is caused by the server 
         software trying to resolve the client's IP address into a hostname.  
         Many servers, including the Telnet and SSH servers that come with    
         FreeBSD, do this to store the hostname in a log file for future      
         reference by the administrator.                                      
                                                                              
         The remedy: if the problem occurs whenever connecting the client     
         computer to any server, the problem is with the client. If the       
         problem only occurs when someone connects to the server computer,    
         the problem is with the server.                                      
                                                                              
         If the problem is with the client, the only remedy is to fix the DNS 
         so the server can resolve it. If this is on a local network,         
         consider it a server problem and keep reading. If this is on the     
         Internet, contact your ISP.                                          
                                                                              
         If the problem is with the server on a local network, configure the  
         server to resolve address-to-hostname queries for the local address  
         range. See hosts(5) and named(8) for more information. If this is on 
         the Internet, the problem may be that the local server's resolver is 
         not functioning correctly. To check, try to look up another host     
         such as www.yahoo.com. If it does not work, that is the problem.     
                                                                              
         Following a fresh install of FreeBSD, it is also possible that       
         domain and name server information is missing from /etc/resolv.conf. 
         This will often cause a delay in SSH, as the option UseDNS is set to 
         yes by default in /etc/ssh/sshd_config. If this is causing the       
         problem, either fill in the missing information in /etc/resolv.conf  
         or set UseDNS to no in sshd_config as a temporary workaround.        
   5.7.  Why does file: table is full show up repeatedly in dmesg(8)?         
         This error message indicates that the number of available file       
         descriptors have been exhausted on the system. Refer to the          
         kern.maxfiles section of the Tuning Kernel Limits section of the     
         Handbook for a discussion and solution.                              
   5.8.  Why does the clock on my computer keep incorrect time?               
         The computer has two or more clocks, and FreeBSD has chosen to use   
         the wrong one.                                                       
                                                                              
         Run dmesg(8), and check for lines that contain Timecounter. The one  
         with the highest quality value that FreeBSD chose.                   
                                                                              
         # dmesg | grep Timecounter                                           
         Timecounter "i8254" frequency 1193182 Hz quality 0                   
         Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000            
         Timecounter "TSC" frequency 2998570050 Hz quality 800                
         Timecounters tick every 1.000 msec                                   
                                                                              
         Confirm this by checking the kern.timecounter.hardware sysctl(3).    
                                                                              
         # sysctl kern.timecounter.hardware                                   
         kern.timecounter.hardware: ACPI-fast                                 
                                                                              
         It may be a broken ACPI timer. The simplest solution is to disable   
         the ACPI timer in /boot/loader.conf:                                 
                                                                              
         debug.acpi.disabled="timer"                                          
                                                                              
         Or the BIOS may modify the TSC clock-perhaps to change the speed of  
         the processor when running from batteries, or going into a power     
         saving mode, but FreeBSD is unaware of these adjustments, and        
         appears to gain or lose time.                                        
                                                                              
         In this example, the i8254 clock is also available, and can be       
         selected by writing its name to the kern.timecounter.hardware        
         sysctl(3).                                                           
                                                                              
         # sysctl kern.timecounter.hardware=i8254                             
         kern.timecounter.hardware: TSC -> i8254                              
                                                                              
         The computer should now start keeping more accurate time.            
                                                                              
         To have this change automatically run at boot time, add the          
         following line to /etc/sysctl.conf:                                  
                                                                              
         kern.timecounter.hardware=i8254                                      
   5.9.  What does the error swap_pager: indefinite wait buffer: mean?        
         This means that a process is trying to page memory from disk, and    
         the page attempt has hung trying to access the disk for more than 20 
         seconds. It might be caused by bad blocks on the disk drive, disk    
         wiring, cables, or any other disk I/O-related hardware. If the drive 
         itself is bad, disk errors will appear in /var/log/messages and in   
         the output of dmesg. Otherwise, check the cables and connections.    
   5.10. What is a lock order reversal?                                       
         The FreeBSD kernel uses a number of resource locks to arbitrate      
         contention for certain resources. When multiple kernel threads try   
         to obtain multiple resource locks, there's always the potential for  
         a deadlock, where two threads have each obtained one of the locks    
         and blocks forever waiting for the other thread to release one of    
         the other locks. This sort of locking problem can be avoided if all  
         threads obtain the locks in the same order.                          
                                                                              
         A run-time lock diagnostic system called witness(4), enabled in      
         FreeBSD-CURRENT and disabled by default for stable branches and      
         releases, detects the potential for deadlocks due to locking errors, 
         including errors caused by obtaining multiple resource locks with a  
         different order from different parts of the kernel. The witness(4)   
         framework tries to detect this problem as it happens, and reports it 
         by printing a message to the system console about a lock order       
         reversal (often referred to also as LOR).                            
                                                                              
         It is possible to get false positives, as witness(4) is              
         conservative. A true positive report does not mean that a system is  
         dead-locked; instead it should be understood as a warning that a     
         deadlock could have happened here.                                   
                                                                              
           Note:                                                              
                                                                              
         Problematic LORs tend to get fixed quickly, so check the             
         FreeBSD-CURRENT mailing list before posting to it.                   
   5.11. What does Called ... with the following non-sleepable locks held     
         mean?                                                                
         This means that a function that may sleep was called while a mutex   
         (or other unsleepable) lock was held.                                
                                                                              
         The reason this is an error is because mutexes are not intended to   
         be held for long periods of time; they are supposed to only be held  
         to maintain short periods of synchronization. This programming       
         contract allows device drivers to use mutexes to synchronize with    
         the rest of the kernel during interrupts. Interrupts (under FreeBSD) 
         may not sleep. Hence it is imperative that no subsystem in the       
         kernel block for an extended period while holding a mutex.           
                                                                              
         To catch such errors, assertions may be added to the kernel that     
         interact with the witness(4) subsystem to emit a warning or fatal    
         error (depending on the system configuration) when a potentially     
         blocking call is made while holding a mutex.                         
                                                                              
         In summary, such warnings are non-fatal, however with unfortunate    
         timing they could cause undesirable effects ranging from a minor     
         blip in the system's responsiveness to a complete system lockup.     
                                                                              
         For additional information about locking in FreeBSD see locking(9).  
   5.12. Why does buildworld/installworld die with the message touch: not     
         found?                                                               
         This error does not mean that the touch(1) utility is missing. The   
         error is instead probably due to the dates of the files being set    
         sometime in the future. If the CMOS clock is set to local time, run  
         adjkerntz -i to adjust the kernel clock when booting into            
         single-user mode.                                                    

                          Chapter 6. User Applications

   6.1. Where are all the user applications?

   6.2. How do I download the Ports tree? Should I be using Subversion?

   6.3. Why can I not build this port on my 11.X -, or 12.X -STABLE machine?

   6.4. I just tried to build INDEX using make index, and it failed. Why?

   6.5. I updated the sources, now how do I update my installed ports?

   6.6. Do I need to recompile every port each time I perform a major version
   update?

   6.7. Do I need to recompile every port each time I perform a minor version
   update?

   6.8. Why is /bin/sh so minimal? Why does FreeBSD not use bash or another
   shell?

   6.1. Where are all the user applications?                                  
        Refer to the ports page for info on software packages ported to       
        FreeBSD.                                                              
                                                                              
        Most ports should work on all supported versions of FreeBSD. Those    
        that do not are specifically marked as such. Each time a FreeBSD      
        release is made, a snapshot of the ports tree at the time of release  
        is also included in the ports/ directory.                             
                                                                              
        FreeBSD supports compressed binary packages to easily install and     
        uninstall ports. Use pkg(7) to control the installation of packages.  
   6.2. How do I download the Ports tree? Should I be using Subversion?       
        Any of the methods listed here work:                                  
                                                                              
          * Use portsnap for most use cases. Refer to Using the Ports         
            Collection for instructions on how to use this tool.              
                                                                              
          * Use Subversion if custom patches to the ports tree are needed or  
            if running FreeBSD-CURRENT. Refer to Using Subversion for         
            details.                                                          
   6.3. Why can I not build this port on my 11.X -, or 12.X -STABLE machine?  
        If the installed FreeBSD version lags significantly behind -CURRENT   
        or -STABLE, update the Ports Collection using the instructions in     
        Using the Ports Collection. If the system is up-to-date, someone      
        might have committed a change to the port which works for -CURRENT    
        but which broke the port for -STABLE. Submit a bug report, since the  
        Ports Collection is supposed to work for both the -CURRENT and        
        -STABLE branches.                                                     
   6.4. I just tried to build INDEX using make index, and it failed. Why?     
        First, make sure that the Ports Collection is up-to-date. Errors that 
        affect building INDEX from an up-to-date copy of the Ports Collection 
        are high-visibility and are thus almost always fixed immediately.     
                                                                              
        There are rare cases where INDEX will not build due to odd cases      
        involving OPTIONS_SET being set in make.conf. If you suspect that     
        this is the case, try to make INDEX with those variables turned off   
        before reporting it to FreeBSD ports mailing list.                    
   6.5. I updated the sources, now how do I update my installed ports?        
        FreeBSD does not include a port upgrading tool, but it does have some 
        tools to make the upgrade process somewhat easier. Additional tools   
        are available to simplify port handling and are described the         
        Upgrading Ports section in the FreeBSD Handbook.                      
   6.6. Do I need to recompile every port each time I perform a major version 
        update?                                                               
        Yes! While a recent system will run with software compiled under an   
        older release, things will randomly crash and fail to work once other 
        ports are installed or updated.                                       
                                                                              
        When the system is upgraded, various shared libraries, loadable       
        modules, and other parts of the system will be replaced with newer    
        versions. Applications linked against the older versions may fail to  
        start or, in other cases, fail to function properly.                  
                                                                              
        For more information, see the section on upgrades in the FreeBSD      
        Handbook.                                                             
   6.7. Do I need to recompile every port each time I perform a minor version 
        update?                                                               
        In general, no. FreeBSD developers do their utmost to guarantee       
        binary compatibility across all releases with the same major version  
        number. Any exceptions will be documented in the Release Notes, and   
        advice given there should be followed.                                
   6.8. Why is /bin/sh so minimal? Why does FreeBSD not use bash or another   
        shell?                                                                
        Many people need to write shell scripts which will be portable across 
        many systems. That is why POSIX(R) specifies the shell and utility    
        commands in great detail. Most scripts are written in Bourne shell    
        (sh(1)), and because several important programming interfaces         
        (make(1), system(3), popen(3), and analogues in higher-level          
        scripting languages like Perl and Tcl) are specified to use the       
        Bourne shell to interpret commands. As the Bourne shell is so often   
        and widely used, it is important for it to be quick to start, be      
        deterministic in its behavior, and have a small memory footprint.     
                                                                              
        The existing implementation is our best effort at meeting as many of  
        these requirements simultaneously as we can. To keep /bin/sh small,   
        we have not provided many of the convenience features that other      
        shells have. That is why other more featureful shells like bash,      
        scsh, tcsh(1), and zsh are available. Compare the memory utilization  
        of these shells by looking at the "VSZ" and "RSS" columns in a ps -u  
        listing.                                                              

                        Chapter 7. Kernel Configuration

   7.1. I would like to customize my kernel. Is it difficult?

   7.2. Why is my kernel so big?

   7.3. Why does every kernel I try to build fail to compile, even GENERIC?

   7.4. Which scheduler is in use on a running system?

   7.5. What is kern.sched.quantum?

   7.1. I would like to customize my kernel. Is it difficult?                 
        Not at all! Check out the kernel config section of the Handbook.      
                                                                              
          Note:                                                               
                                                                              
        The new kernel will be installed to the /boot/kernel directory along  
        with its modules, while the old kernel and its modules will be moved  
        to the /boot/kernel.old directory. If a mistake is made in the        
        configuration, simply boot the previous version of the kernel.        
   7.2. Why is my kernel so big?                                              
        GENERIC kernels shipped with FreeBSD are compiled in debug mode.      
        Kernels built in debug mode contain debug data in separate files that 
        are used for debugging. FreeBSD releases prior to 11.0 store these    
        debug files in the same directory as the kernel itself,               
        /boot/kernel/. In FreeBSD 11.0 and later the debug files are stored   
        in /usr/lib/debug/boot/kernel/. Note that there will be little or no  
        performance loss from running a debug kernel, and it is useful to     
        keep one around in case of a system panic.                            
                                                                              
        When running low on disk space, there are different options to reduce 
        the size of /boot/kernel/ and /usr/lib/debug/.                        
                                                                              
        To not install the symbol files, make sure the following line exists  
        in /etc/src.conf:                                                     
                                                                              
        WITHOUT_KERNEL_SYMBOLS=yes                                            
                                                                              
        For more information see src.conf(5).                                 
                                                                              
        If you want to avoid building debug files altogether, make sure that  
        both of the following are true:                                       
                                                                              
          * This line does not exist in the kernel configuration file:        
                                                                              
         makeoptions DEBUG=-g                                                 
                                                                              
          * Do not run config(8) with -g.                                     
                                                                              
        Either of the above settings will cause the kernel to be built in     
        debug mode.                                                           
                                                                              
        To build and install only the specified modules, list them in         
        /etc/make.conf:                                                       
                                                                              
        MODULES_OVERRIDE= accf_http ipfw                                      
                                                                              
        Replace accf_httpd ipfw with a list of needed modules. Only the       
        listed modules will be built. This reduces the size of the kernel     
        directory and decreases the amount of time needed to build the        
        kernel. For more information, read /usr/share/examples/etc/make.conf. 
                                                                              
        Unneeded devices can be removed from the kernel to further reduce the 
        size. See Q: 7.1 for more information.                                
                                                                              
        To put any of these options into effect, follow the instructions to   
        build and install the new kernel.                                     
                                                                              
        For reference, the FreeBSD 11 amd64 kernel (/boot/kernel/kernel) is   
        approximately 25 MB.                                                  
   7.3. Why does every kernel I try to build fail to compile, even GENERIC?   
        There are a number of possible causes for this problem:               
                                                                              
          * The source tree is different from the one used to build the       
            currently running system. When attempting an upgrade, read        
            /usr/src/UPDATING, paying particular attention to the "COMMON     
            ITEMS" section at the end.                                        
                                                                              
          * The make buildkernel did not complete successfully. The make      
            buildkernel target relies on files generated by the make          
            buildworld target to complete its job correctly.                  
                                                                              
          * Even when building FreeBSD-STABLE, it is possible that the source 
            tree was fetched at a time when it was either being modified or   
            it was broken. Only releases are guaranteed to be buildable,      
            although FreeBSD-STABLE builds fine the majority of the time. Try 
            re-fetching the source tree and see if the problem goes away. Try 
            using a different mirror in case the previous one is having       
            problems.                                                         
   7.4. Which scheduler is in use on a running system?                        
        The name of the scheduler currently being used is directly available  
        as the value of the kern.sched.name sysctl:                           
                                                                              
        % sysctl kern.sched.name                                              
        kern.sched.name: ULE                                                  
   7.5. What is kern.sched.quantum?                                           
        kern.sched.quantum is the maximum number of ticks a process can run   
        without being preempted in the 4BSD scheduler.                        

                Chapter 8. Disks, File Systems, and Boot Loaders

   8.1. How can I add my new hard disk to my FreeBSD system?

   8.2. How do I move my system over to my huge new disk?

   8.3. Which partitions can safely use Soft Updates? I have heard that Soft
   Updates on / can cause problems. What about Journaled Soft Updates?

   8.4. Can I mount other foreign file systems under FreeBSD?

   8.5. How do I mount a secondary DOS partition?

   8.6. Is there a cryptographic file system for FreeBSD?

   8.7. How do I boot FreeBSD and Linux(R) using GRUB?

   8.8. How do I boot FreeBSD and Linux(R) using BootEasy?

   8.9. How do I change the boot prompt from ??? to something more
   meaningful?

   8.10. How do I use a new removable drive?

   8.11. Why do I get Incorrect super block when mounting a CD?

   8.12. Why do I get Device not configured when mounting a CD?

   8.13. Why do all non-English characters in filenames show up as "?" on my
   CDs when mounted in FreeBSD?

   8.14. A CD burned under FreeBSD cannot be read under any other operating
   system. Why?

   8.15. How can I create an image of a data CD?

   8.16. Why can I not mount an audio CD?

   8.17. How do I mount a multi-session CD?

   8.18. How do I let ordinary users mount CD-ROMs, DVDs, USB drives, and
   other removable media?

   8.19. The du and df commands show different amounts of disk space
   available. What is going on?

   8.20. How can I add more swap space?

   8.21. Why does FreeBSD see my disk as smaller than the manufacturer says
   it is?

   8.22. How is it possible for a partition to be more than 100% full?

   8.1.  How can I add my new hard disk to my FreeBSD system?                 
         See the Adding Disks section in the FreeBSD Handbook.                
   8.2.  How do I move my system over to my huge new disk?                    
         The best way is to reinstall the operating system on the new disk,   
         then move the user data over. This is highly recommended when        
         tracking -STABLE for more than one release or when updating a        
         release instead of installing a new one. Install booteasy on both    
         disks with boot0cfg(8) and dual boot until you are happy with the    
         new configuration. Skip the next paragraph to find out how to move   
         the data after doing this.                                           
                                                                              
         Alternatively, partition and label the new disk with either sade(8)  
         or gpart(8). If the disks are MBR-formatted, booteasy can be         
         installed on both disks with boot0cfg(8) so that the computer can    
         dual boot to the old or new system after the copying is done.        
                                                                              
         Once the new disk set up, the data cannot just be copied. Instead,   
         use tools that understand device files and system flags, such as     
         dump(8). Although it is recommended to move the data while in        
         single-user mode, it is not required.                                
                                                                              
         When the disks are formatted with UFS, never use anything but        
         dump(8) and restore(8) to move the root file system. These commands  
         should also be used when moving a single partition to another empty  
         partition. The sequence of steps to use dump to move the data from   
         one UFS partitions to a new partition is:                            
                                                                              
          1. newfs the new partition.                                         
                                                                              
          2. mount it on a temporary mount point.                             
                                                                              
          3. cd to that directory.                                            
                                                                              
          4. dump the old partition, piping output to the new one.            
                                                                              
         For example, to move /dev/ada1s1a with /mnt as the temporary mount   
         point, type:                                                         
                                                                              
         # newfs /dev/ada1s1a                                                 
         # mount /dev/ada1s1a /mnt                                            
         # cd /mnt                                                            
         # dump 0af - / | restore rf -                                        
                                                                              
         Rearranging partitions with dump takes a bit more work. To merge a   
         partition like /var into its parent, create the new partition large  
         enough for both, move the parent partition as described above, then  
         move the child partition into the empty directory that the first     
         move created:                                                        
                                                                              
         # newfs /dev/ada1s1a                                                 
         # mount /dev/ada1s1a /mnt                                            
         # cd /mnt                                                            
         # dump 0af - / | restore rf -                                        
         # cd var                                                             
         # dump 0af - /var | restore rf -                                     
                                                                              
         To split a directory from its parent, say putting /var on its own    
         partition when it was not before, create both partitions, then mount 
         the child partition on the appropriate directory in the temporary    
         mount point, then move the old single partition:                     
                                                                              
         # newfs /dev/ada1s1a                                                 
         # newfs /dev/ada1s1d                                                 
         # mount /dev/ada1s1a /mnt                                            
         # mkdir /mnt/var                                                     
         # mount /dev/ada1s1d /mnt/var                                        
         # cd /mnt                                                            
         # dump 0af - / | restore rf -                                        
                                                                              
         The cpio(1) and pax(1) utilities are also available for moving user  
         data. These are known to lose file flag information, so use them     
         with caution.                                                        
   8.3.  Which partitions can safely use Soft Updates? I have heard that Soft 
         Updates on / can cause problems. What about Journaled Soft Updates?  
         Short answer: Soft Updates can usually be safely used on all         
         partitions.                                                          
                                                                              
         Long answer: Soft Updates has two characteristics that may be        
         undesirable on certain partitions. First, a Soft Updates partition   
         has a small chance of losing data during a system crash. The         
         partition will not be corrupted as the data will simply be lost.     
         Second, Soft Updates can cause temporary space shortages.            
                                                                              
         When using Soft Updates, the kernel can take up to thirty seconds to 
         write changes to the physical disk. When a large file is deleted the 
         file still resides on disk until the kernel actually performs the    
         deletion. This can cause a very simple race condition. Suppose one   
         large file is deleted and another large file is immediately created. 
         The first large file is not yet actually removed from the physical   
         disk, so the disk might not have enough room for the second large    
         file. This will produce an error that the partition does not have    
         enough space, even though a large chunk of space has just been       
         released. A few seconds later, the file creation works as expected.  
                                                                              
         If a system should crash after the kernel accepts a chunk of data    
         for writing to disk, but before that data is actually written out,   
         data could be lost. This risk is extremely small, but generally      
         manageable.                                                          
                                                                              
         These issues affect all partitions using Soft Updates. So, what does 
         this mean for the root partition?                                    
                                                                              
         Vital information on the root partition changes very rarely. If the  
         system crashed during the thirty-second window after such a change   
         is made, it is possible that data could be lost. This risk is        
         negligible for most applications, but be aware that it exists. If    
         the system cannot tolerate this much risk, do not use Soft Updates   
         on the root file system!                                             
                                                                              
         / is traditionally one of the smallest partitions. If /tmp is on /,  
         there may be intermittent space problems. Symlinking /tmp to         
         /var/tmp will solve this problem.                                    
                                                                              
         Finally, dump(8) does not work in live mode (-L) on a filesystem,    
         with Journaled Soft Updates (SU+J).                                  
   8.4.  Can I mount other foreign file systems under FreeBSD?                
         FreeBSD supports a variety of other file systems.                    
                                                                              
         UFS                                                                  
                                                                              
            UFS CD-ROMs can be mounted directly on FreeBSD. Mounting disk     
            partitions from Digital UNIX and other systems that support UFS   
            may be more complex, depending on the details of the disk         
            partitioning for the operating system in question.                
                                                                              
         ext2/ext3                                                            
                                                                              
            FreeBSD supports ext2fs and ext3fs partitions. See ext2fs(5) for  
            more information.                                                 
                                                                              
         NTFS                                                                 
                                                                              
            FUSE based NTFS support is available as a port                    
            (sysutils/fusefs-ntfs). For more information see ntfs-3g.         
                                                                              
         FAT                                                                  
                                                                              
            FreeBSD includes a read-write FAT driver. For more information,   
            see mount_msdosfs(8).                                             
                                                                              
         ZFS                                                                  
                                                                              
            FreeBSD includes a port of Sun(TM)'s ZFS driver. The current      
            recommendation is to use it only on amd64 platforms with          
            sufficient memory. For more information, see zfs(8).              
                                                                              
         FreeBSD includes the Network File System NFS and the FreeBSD Ports   
         Collection provides several FUSE applications to support many other  
         file systems.                                                        
   8.5.  How do I mount a secondary DOS partition?                            
         The secondary DOS partitions are found after all the primary         
         partitions. For example, if E is the second DOS partition on the     
         second SCSI drive, there will be a device file for "slice 5" in      
         /dev. To mount it:                                                   
                                                                              
         # mount -t msdosfs /dev/da1s5 /dos/e                                 
   8.6.  Is there a cryptographic file system for FreeBSD?                    
         Yes, gbde(8) and geli(8). See the Encrypting Disk Partitions section 
         of the FreeBSD Handbook.                                             
   8.7.  How do I boot FreeBSD and Linux(R) using GRUB?                       
         To boot FreeBSD using GRUB, add the following to either              
         /boot/grub/menu.lst or /boot/grub/grub.conf, depending upon which is 
         used by the Linux(R) distribution.                                   
                                                                              
         title FreeBSD 9.1                                                    
                 root (hd0,a)                                                 
                 kernel /boot/loader                                          
                                                                              
         Where hd0,a points to the root partition on the first disk. To       
         specify the slice number, use something like this (hd0,2,a). By      
         default, if the slice number is omitted, GRUB searches the first     
         slice which has the a partition.                                     
   8.8.  How do I boot FreeBSD and Linux(R) using BootEasy?                   
         Install LILO at the start of the Linux(R) boot partition instead of  
         in the Master Boot Record. Then boot LILO from BootEasy.             
                                                                              
         This is recommended when running Windows(R) and Linux(R) as it makes 
         it simpler to get Linux(R) booting again if Windows(R) is            
         reinstalled.                                                         
   8.9.  How do I change the boot prompt from ??? to something more           
         meaningful?                                                          
         This cannot be accomplished with the standard boot manager without   
         rewriting it. There are a number of other boot managers in the       
         sysutils category of the Ports Collection.                           
   8.10. How do I use a new removable drive?                                  
         If the drive already has a file system on it, use a command like     
         this:                                                                
                                                                              
         # mount -t msdosfs /dev/da0s1 /mnt                                   
                                                                              
         If the drive will only be used with FreeBSD systems, partition it    
         with UFS or ZFS. This will provide long filename support,            
         improvement in performance, and stability. If the drive will be used 
         by other operating systems, a more portable choice, such as msdosfs, 
         is better.                                                           
                                                                              
         # dd if=/dev/zero of=/dev/da0 count=2                                
         # gpart create -s GPT /dev/da0                                       
         # gpart add -t freebsd-ufs /dev/da0                                  
                                                                              
         Finally, create a new file system:                                   
                                                                              
         # newfs /dev/da0p1                                                   
                                                                              
         and mount it:                                                        
                                                                              
         # mount /dev/da0s1 /mnt                                              
                                                                              
         It is a good idea to add a line to /etc/fstab (see fstab(5)) so you  
         can just type mount /mnt in the future:                              
                                                                              
         /dev/da0p1 /mnt ufs rw,noauto 0 0                                    
   8.11. Why do I get Incorrect super block when mounting a CD?               
         The type of device to mount must be specified. This is described in  
         the Handbook section on Using Data CDs.                              
   8.12. Why do I get Device not configured when mounting a CD?               
         This generally means that there is no CD in the drive, or the drive  
         is not visible on the bus. Refer to the Using Data CDs section of    
         the Handbook for a detailed discussion of this issue.                
   8.13. Why do all non-English characters in filenames show up as "?" on my  
         CDs when mounted in FreeBSD?                                         
         The CD probably uses the "Joliet" extension for storing information  
         about files and directories. This is discussed in the Handbook       
         section on Using Data CD-ROMs.                                       
   8.14. A CD burned under FreeBSD cannot be read under any other operating   
         system. Why?                                                         
         This means a raw file was burned to the CD, rather than creating an  
         ISO 9660 file system. Take a look at the Handbook section on Using   
         Data CDs.                                                            
   8.15. How can I create an image of a data CD?                              
         This is discussed in the Handbook section on Writing Data to an ISO  
         File System. For more on working with CD-ROMs, see the Creating CDs  
         Section in the Storage chapter in the Handbook.                      
   8.16. Why can I not mount an audio CD?                                     
         Trying to mount an audio CD will produce an error like cd9660:       
         /dev/cd0: Invalid argument. This is because mount only works on file 
         systems. Audio CDs do not have file systems; they just have data.    
         Instead, use a program that reads audio CDs, such as the audio/xmcd  
         package or port.                                                     
   8.17. How do I mount a multi-session CD?                                   
         By default, mount(8) will attempt to mount the last data track       
         (session) of a CD. To load an earlier session, use the -s command    
         line argument. Refer to mount_cd9660(8) for specific examples.       
   8.18. How do I let ordinary users mount CD-ROMs, DVDs, USB drives, and     
         other removable media?                                               
         As root set the sysctl variable vfs.usermount to 1.                  
                                                                              
         # sysctl vfs.usermount=1                                             
                                                                              
         To make this persist across reboots, add the line vfs.usermount=1 to 
         /etc/sysctl.conf so that it is reset at system boot time.            
                                                                              
         Users can only mount devices they have read permissions to. To allow 
         users to mount a device permissions must be set in /etc/devfs.conf.  
                                                                              
         For example, to allow users to mount the first USB drive add:        
                                                                              
         # Allow all users to mount a USB drive.                              
                     own       /dev/da0       root:operator                   
                     perm      /dev/da0       0666                            
                                                                              
         All users can now mount devices they could read onto a directory     
         that they own:                                                       
                                                                              
         % mkdir ~/my-mount-point                                             
         % mount -t msdosfs /dev/da0 ~/my-mount-point                         
                                                                              
         Unmounting the device is simple:                                     
                                                                              
         % umount ~/my-mount-point                                            
                                                                              
         Enabling vfs.usermount, however, has negative security implications. 
         A better way to access MS-DOS(R) formatted media is to use the       
         emulators/mtools package in the Ports Collection.                    
                                                                              
           Note:                                                              
                                                                              
         The device name used in the previous examples must be changed        
         according to the configuration.                                      
   8.19. The du and df commands show different amounts of disk space          
         available. What is going on?                                         
         This is due to how these commands actually work. du goes through the 
         directory tree, measures how large each file is, and presents the    
         totals. df just asks the file system how much space it has left.     
         They seem to be the same thing, but a file without a directory entry 
         will affect df but not du.                                           
                                                                              
         When a program is using a file, and the file is deleted, the file is 
         not really removed from the file system until the program stops      
         using it. The file is immediately deleted from the directory         
         listing, however. As an example, consider a file large enough to     
         affect the output of du and df. A file being viewed with more can be 
         deleted wihout causing an error. The entry is removed from the       
         directory so no other program or user can access it. However, du     
         shows that it is gone as it has walked the directory tree and the    
         file is not listed. df shows that it is still there, as the file     
         system knows that more is still using that space. Once the more      
         session ends, du and df will agree.                                  
                                                                              
         This situation is common on web servers. Many people set up a        
         FreeBSD web server and forget to rotate the log files. The access    
         log fills up /var. The new administrator deletes the file, but the   
         system still complains that the partition is full. Stopping and      
         restarting the web server program would free the file, allowing the  
         system to release the disk space. To prevent this from happening,    
         set up newsyslog(8).                                                 
                                                                              
         Note that Soft Updates can delay the freeing of disk space and it    
         can take up to 30 seconds for the change to be visible.              
   8.20. How can I add more swap space?                                       
         This section of the Handbook describes how to do this.               
   8.21. Why does FreeBSD see my disk as smaller than the manufacturer says   
         it is?                                                               
         Disk manufacturers calculate gigabytes as a billion bytes each,      
         whereas FreeBSD calculates them as 1,073,741,824 bytes each. This    
         explains why, for example, FreeBSD's boot messages will report a     
         disk that supposedly has 80 GB as holding 76,319 MB.                 
                                                                              
         Also note that FreeBSD will (by default) reserve 8% of the disk      
         space.                                                               
   8.22. How is it possible for a partition to be more than 100% full?        
         A portion of each UFS partition (8%, by default) is reserved for use 
         by the operating system and the root user. df(1) does not count that 
         space when calculating the Capacity column, so it can exceed 100%.   
         Notice that the Blocks column is always greater than the sum of the  
         Used and Avail columns, usually by a factor of 8%.                   
                                                                              
         For more details, look up -m in tunefs(8).                           

                                 Chapter 9. ZFS

   9.1. What is the minimum amount of RAM one should have to run ZFS?

   9.2. What is the ZIL and when does it get used?

   9.3. Do I need a SSD for ZIL?

   9.4. What is the L2ARC?

   9.5. Is enabling deduplication advisable?

   9.6. I cannot delete or create files on my ZFS pool. How can I fix this?

   9.7. Does ZFS support TRIM for Solid State Drives?

   9.1. What is the minimum amount of RAM one should have to run ZFS?         
        A minimum of 4GB of RAM is required for comfortable usage, but        
        individual workloads can vary widely.                                 
   9.2. What is the ZIL and when does it get used?                            
        The ZIL (ZFS intent log) is a write log used to implement posix write 
        commitment semantics across crashes. Normally writes are bundled up   
        into transaction groups and written to disk when filled ("Transaction 
        Group Commit"). However syscalls like fsync(2) require a commitment   
        that the data is written to stable storage before returning. The ZIL  
        is needed for writes that have been acknowledged as written but which 
        are not yet on disk as part of a transaction. The transaction groups  
        are timestamped. In the event of a crash the last valid timestamp is  
        found and missing data is merged in from the ZIL.                     
   9.3. Do I need a SSD for ZIL?                                              
        By default, ZFS stores the ZIL in the pool with all the data. If an   
        application has a heavy write load, storing the ZIL in a separate     
        device that has very fast synchronous, sequential write performance   
        can improve overall system performance. For other workloads, a SSD is 
        unlikely to make much of an improvement.                              
   9.4. What is the L2ARC?                                                    
        The L2ARC is a read cache stored on a fast device such as an SSD.     
        This cache is not persistent across reboots. Note that RAM is used as 
        the first layer of cache and the L2ARC is only needed if there is     
        insufficient RAM.                                                     
                                                                              
        L2ARC needs space in the ARC to index it. So, perversely, a working   
        set that fits perfectly in the ARC will not fit perfectly any more if 
        a L2ARC is used because part of the ARC is holding the L2ARC index,   
        pushing part of the working set into the L2ARC which is slower than   
        RAM.                                                                  
   9.5. Is enabling deduplication advisable?                                  
        Generally speaking, no.                                               
                                                                              
        Deduplication takes up a significant amount of RAM and may slow down  
        read and write disk access times. Unless one is storing data that is  
        very heavily duplicated, such as virtual machine images or user       
        backups, it is possible that deduplication will do more harm than     
        good. Another consideration is the inability to revert deduplication  
        status. If data is written when deduplication is enabled, disabling   
        dedup will not cause those blocks which were deduplicated to be       
        replicated until they are next modified.                              
                                                                              
        Deduplication can also lead to some unexpected situations. In         
        particular, deleting files may become much slower.                    
   9.6. I cannot delete or create files on my ZFS pool. How can I fix this?   
        This could happen because the pool is 100% full. ZFS requires space   
        on the disk to write transaction metadata. To restore the pool to a   
        usable state, truncate the file to delete:                            
                                                                              
        % truncate -s 0 unimportant-file                                      
                                                                              
        File truncation works because a new transaction is not started, new   
        spare blocks are created instead.                                     
                                                                              
          Note:                                                               
                                                                              
        On systems with additional ZFS dataset tuning, such as deduplication, 
        the space may not be immediately available                            
   9.7. Does ZFS support TRIM for Solid State Drives?                         
        ZFS TRIM support was added to FreeBSD 10-CURRENT with revision        
        r240868. ZFS TRIM support was added to all FreeBSD-STABLE branches in 
        r252162 and r251419, respectively.                                    
                                                                              
        ZFS TRIM is enabled by default, and can be turned off by adding this  
        line to /etc/sysctl.conf:                                             
                                                                              
        vfs.zfs.trim.enabled=0                                                
                                                                              
          Note:                                                               
                                                                              
        ZFS TRIM support was added to GELI as of r286444. Please see geli(8)  
        and the -T switch.                                                    

                       Chapter 10. System Administration

   10.1. Where are the system start-up configuration files?

   10.2. How do I add a user easily?

   10.3. Why do I keep getting messages like root: not found after editing
   /etc/crontab?

   10.4. Why do I get the error, you are not in the correct group to su root
   when I try to su to root?

   10.5. I made a mistake in rc.conf, or another startup file, and now I
   cannot edit it because the file system is read-only. What should I do?

   10.6. Why am I having trouble setting up my printer?

   10.7. How can I correct the keyboard mappings for my system?

   10.8. Why can I not get user quotas to work properly?

   10.9. Does FreeBSD support System V IPC primitives?

   10.10. What other mail-server software can I use instead of Sendmail?

   10.11. I have forgotten the root password! What do I do?

   10.12. How do I keep Control+Alt+Delete from rebooting the system?

   10.13. How do I reformat DOS text files to UNIX(R) ones?

   10.14. How do I re-read /etc/rc.conf and re-start /etc/rc without a
   reboot?

   10.15. I tried to update my system to the latest -STABLE, but got -BETAx,
   -RC or -PRERELEASE! What is going on?

   10.16. I tried to install a new kernel, and the chflags(1) failed. How do
   I get around this?

   10.17. I cannot change the time on my system by more than one second! How
   do I get around this?

   10.18. Why is rpc.statd using 256 MB of memory?

   10.19. Why can I not unset the schg file flag?

   10.20. What is vnlru?

   10.21. What do the various memory states displayed by top mean?

   10.22. How much free memory is available?

   10.23. What is /var/empty?

   10.24. I just changed /etc/newsyslog.conf. How can I check if it does what
   I expect?

   10.25. My time is wrong, how can I change the timezone?

   10.1.  Where are the system start-up configuration files?                  
          The primary configuration file is /etc/defaults/rc.conf which is    
          described in rc.conf(5). System startup scripts such as /etc/rc and 
          /etc/rc.d, which are described in rc(8), include this file. Do not  
          edit this file! Instead, to edit an entry in /etc/defaults/rc.conf, 
          copy the line into /etc/rc.conf and change it there.                
                                                                              
          For example, if to start named(8), the included DNS server:         
                                                                              
          # echo 'named_enable="YES"' >> /etc/rc.conf                         
                                                                              
          To start up local services, place shell scripts in the              
          /usr/local/etc/rc.d directory. These shell scripts should be set    
          executable, the default file mode is 555.                           
   10.2.  How do I add a user easily?                                         
          Use the adduser(8) command, or the pw(8) command for more           
          complicated situations.                                             
                                                                              
          To remove the user, use the rmuser(8) command or, if necessary,     
          pw(8).                                                              
   10.3.  Why do I keep getting messages like root: not found after editing   
          /etc/crontab?                                                       
          This is normally caused by editing the system crontab. This is not  
          the correct way to do things as the system crontab has a different  
          format to the per-user crontabs. The system crontab has an extra    
          field, specifying which user to run the command as. cron(8) assumes 
          this user is the first word of the command to execute. Since no     
          such command exists, this error message is displayed.               
                                                                              
          To delete the extra, incorrect crontab:                             
                                                                              
          # crontab -r                                                        
   10.4.  Why do I get the error, you are not in the correct group to su root 
          when I try to su to root?                                           
          This is a security feature. In order to su to root, or any other    
          account with superuser privileges, the user account must be a       
          member of the wheel group. If this feature were not there, anybody  
          with an account on a system who also found out root's password      
          would be able to gain superuser level access to the system.         
                                                                              
          To allow someone to su to root, put them in the wheel group using   
          pw:                                                                 
                                                                              
          # pw groupmod wheel -m lisa                                         
                                                                              
          The above example will add user lisa to the group wheel.            
   10.5.  I made a mistake in rc.conf, or another startup file, and now I     
          cannot edit it because the file system is read-only. What should I  
          do?                                                                 
          Restart the system using boot -s at the loader prompt to enter      
          single-user mode. When prompted for a shell pathname, press Enter   
          and run mount -urw / to re-mount the root file system in read/write 
          mode. You may also need to run mount -a -t ufs to mount the file    
          system where your favorite editor is defined. If that editor is on  
          a network file system, either configure the network manually before 
          mounting the network file systems, or use an editor which resides   
          on a local file system, such as ed(1).                              
                                                                              
          In order to use a full screen editor such as vi(1) or emacs(1), run 
          export TERM=xterm so that these editors can load the correct data   
          from the termcap(5) database.                                       
                                                                              
          After performing these steps, edit /etc/rc.conf to fix the syntax   
          error. The error message displayed immediately after the kernel     
          boot messages should indicate the number of the line in the file    
          which is at fault.                                                  
   10.6.  Why am I having trouble setting up my printer?                      
          See the Handbook entry on printing for troubleshooting tips.        
   10.7.  How can I correct the keyboard mappings for my system?              
          Refer to the Handbook section on using localization, specifically   
          the section on console setup.                                       
   10.8.  Why can I not get user quotas to work properly?                     
           1. It is possible that the kernel is not configured to use quotas. 
              In this case, add the following line to the kernel              
              configuration file and recompile the kernel:                    
                                                                              
           options QUOTA                                                      
                                                                              
              Refer to the Handbook entry on quotas for full details.         
                                                                              
           2. Do not turn on quotas on /.                                     
                                                                              
           3. Put the quota file on the file system that the quotas are to be 
              enforced on:                                                    
                                                                              
                      File System                      Quota file             
              /usr                         /usr/admin/quotas                  
              /home                        /home/admin/quotas                 
              ...                          ...                                
   10.9.  Does FreeBSD support System V IPC primitives?                       
          Yes, FreeBSD supports System V-style IPC, including shared memory,  
          messages and semaphores, in the GENERIC kernel. With a custom       
          kernel, support may be loaded with the sysvshm.ko, sysvsem.ko and   
          sysvmsg.ko kernel modules, or enabled in the custom kernel by       
          adding the following lines to the kernel configuration file:        
                                                                              
          options    SYSVSHM          # enable shared memory                  
          options    SYSVSEM          # enable for semaphores                 
          options    SYSVMSG          # enable for messaging                  
                                                                              
          Recompile and install the kernel.                                   
   10.10. What other mail-server software can I use instead of Sendmail?      
          The Sendmail server is the default mail-server software for         
          FreeBSD, but it can be replaced with another MTA installed from the 
          Ports Collection. Available ports include mail/exim, mail/postfix,  
          and mail/qmail. Search the mailing lists for discussions regarding  
          the advantages and disadvantages of the available MTAs.             
   10.11. I have forgotten the root password! What do I do?                   
          Do not panic! Restart the system, type boot -s at the Boot: prompt  
          to enter single-user mode. At the question about the shell to use,  
          hit Enter which will display a # prompt. Enter mount -urw / to      
          remount the root file system read/write, then run mount -a to       
          remount all the file systems. Run passwd root to change the root    
          password then run exit(1) to continue booting.                      
                                                                              
            Note:                                                             
                                                                              
          If you are still prompted to give the root password when entering   
          the single-user mode, it means that the console has been marked as  
          insecure in /etc/ttys. In this case, it will be required to boot    
          from a FreeBSD installation disk, choose the Live CD or Shell at    
          the beginning of the install process and issue the commands         
          mentioned above. Mount the specific partition in this case and then 
          chroot to it. For example, replace mount -urw / with mount          
          /dev/ada0p1 /mnt; chroot /mnt for a system on ada0p1.               
                                                                              
            Note:                                                             
                                                                              
          If the root partition cannot be mounted from single-user mode, it   
          is possible that the partitions are encrypted and it is impossible  
          to mount them without the access keys. For more information see the 
          section about encrypted disks in the FreeBSD Handbook.              
   10.12. How do I keep Control+Alt+Delete from rebooting the system?         
          When using vt(4), the default console driver, this can be done by   
          setting the following sysctl(8):                                    
                                                                              
          # sysctl kern.vt.kbd_reboot=0                                       
   10.13. How do I reformat DOS text files to UNIX(R) ones?                   
          Use this perl(1) command:                                           
                                                                              
          % perl -i.bak -npe 's/\r\n/\n/g' file(s)                            
                                                                              
          where file(s) is one or more files to process. The modification is  
          done in-place, with the original file stored with a .bak extension. 
                                                                              
          Alternatively, use tr(1):                                           
                                                                              
          % tr -d '\r' < dos-text-file > unix-file                            
                                                                              
          dos-text-file is the file containing DOS text while unix-file will  
          contain the converted output. This can be quite a bit faster than   
          using perl.                                                         
                                                                              
          Yet another way to reformat DOS text files is to use the            
          converters/dosunix port from the Ports Collection. Consult its      
          documentation about the details.                                    
   10.14. How do I re-read /etc/rc.conf and re-start /etc/rc without a        
          reboot?                                                             
          Go into single-user mode and then back to multi-user mode:          
                                                                              
          # shutdown now                                                      
          # return                                                            
          # exit                                                              
   10.15. I tried to update my system to the latest -STABLE, but got -BETAx,  
          -RC or -PRERELEASE! What is going on?                               
          Short answer: it is just a name. RC stands for "Release Candidate". 
          It signifies that a release is imminent. In FreeBSD, -PRERELEASE is 
          typically synonymous with the code freeze before a release. (For    
          some releases, the -BETA label was used in the same way as          
          -PRERELEASE.)                                                       
                                                                              
          Long answer: FreeBSD derives its releases from one of two places.   
          Major, dot-zero, releases, such as 9.0-RELEASE are branched from    
          the head of the development stream, commonly referred to as         
          -CURRENT. Minor releases, such as 6.3-RELEASE or 5.2-RELEASE, have  
          been snapshots of the active -STABLE branch. Starting with          
          4.3-RELEASE, each release also now has its own branch which can be  
          tracked by people requiring an extremely conservative rate of       
          development (typically only security advisories).                   
                                                                              
          When a release is about to be made, the branch from which it will   
          be derived from has to undergo a certain process. Part of this      
          process is a code freeze. When a code freeze is initiated, the name 
          of the branch is changed to reflect that it is about to become a    
          release. For example, if the branch used to be called 6.2-STABLE,   
          its name will be changed to 6.3-PRERELEASE to signify the code      
          freeze and signify that extra pre-release testing should be         
          happening. Bug fixes can still be committed to be part of the       
          release. When the source code is in shape for the release the name  
          will be changed to 6.3-RC to signify that a release is about to be  
          made from it. Once in the RC stage, only the most critical bugs     
          found can be fixed. Once the release (6.3-RELEASE in this example)  
          and release branch have been made, the branch will be renamed to    
          6.3-STABLE.                                                         
                                                                              
          For more information on version numbers and the various Subversion  
          branches, refer to the Release Engineering article.                 
   10.16. I tried to install a new kernel, and the chflags(1) failed. How do  
          I get around this?                                                  
          Short answer: the security level is greater than 0. Reboot directly 
          to single-user mode to install the kernel.                          
                                                                              
          Long answer: FreeBSD disallows changing system flags at security    
          levels greater than 0. To check the current security level:         
                                                                              
          # sysctl kern.securelevel                                           
                                                                              
          The security level cannot be lowered in multi-user mode, so boot to 
          single-user mode to install the kernel, or change the security      
          level in /etc/rc.conf then reboot. See the init(8) manual page for  
          details on securelevel, and see /etc/defaults/rc.conf and the       
          rc.conf(5) manual page for more information on rc.conf.             
   10.17. I cannot change the time on my system by more than one second! How  
          do I get around this?                                               
          Short answer: the system is at a security level greater than 1.     
          Reboot directly to single-user mode to change the date.             
                                                                              
          Long answer: FreeBSD disallows changing the time by more that one   
          second at security levels greater than 1. To check the security     
          level:                                                              
                                                                              
          # sysctl kern.securelevel                                           
                                                                              
          The security level cannot be lowered in multi-user mode. Either     
          boot to single-user mode to change the date or change the security  
          level in /etc/rc.conf and reboot. See the init(8) manual page for   
          details on securelevel, and see /etc/defaults/rc.conf and the       
          rc.conf(5) manual page for more information on rc.conf.             
   10.18. Why is rpc.statd using 256 MB of memory?                            
          No, there is no memory leak, and it is not using 256 MB of memory.  
          For convenience, rpc.statd maps an obscene amount of memory into    
          its address space. There is nothing terribly wrong with this from a 
          technical standpoint; it just throws off things like top(1) and     
          ps(1).                                                              
                                                                              
          rpc.statd(8) maps its status file (resident on /var) into its       
          address space; to save worrying about remapping the status file     
          later when it needs to grow, it maps the status file with a         
          generous size. This is very evident from the source code, where one 
          can see that the length argument to mmap(2) is 0x10000000, or one   
          sixteenth of the address space on an IA32, or exactly 256 MB.       
   10.19. Why can I not unset the schg file flag?                             
          The system is running at securelevel greater than 0. Lower the      
          securelevel and try again. For more information, see the FAQ entry  
          on securelevel and the init(8) manual page.                         
   10.20. What is vnlru?                                                      
          vnlru flushes and frees vnodes when the system hits the             
          kern.maxvnodes limit. This kernel thread sits mostly idle, and only 
          activates when there is a huge amount of RAM and users are          
          accessing tens of thousands of tiny files.                          
   10.21. What do the various memory states displayed by top mean?            
            * Active: pages recently statistically used.                      
                                                                              
            * Inactive: pages recently statistically unused.                  
                                                                              
            * Laundry: pages recently statistically unused but known to be    
              dirty, that is, whose contents needs to be paged out before     
              they can be reused.                                             
                                                                              
            * Free: pages without data content, which can be immediately      
              reused.                                                         
                                                                              
            * Wired: pages that are fixed into memory, usually for kernel     
              purposes, but also sometimes for special use in processes.      
                                                                              
          Pages are most often written to disk (sort of a VM sync) when they  
          are in the laundry state, but active or inactive pages can also be  
          synced. This depends upon the CPU tracking of the modified bit      
          being available, and in certain situations there can be an          
          advantage for a block of VM pages to be synced, regardless of the   
          queue they belong to. In most common cases, it is best to think of  
          the laundry queue as a queue of relatively unused pages that might  
          or might not be in the process of being written to disk. The        
          inactive queue contains a mix of clean and dirty pages; clean pages 
          near the head of the queue are reclaimed immediately to alleviate a 
          free page shortage, and dirty pages are moved to the laundry queue  
          for deferred processing.                                            
                                                                              
          There are some other flags (e.g., busy flag or busy count) that     
          might modify some of the described rules.                           
   10.22. How much free memory is available?                                  
          There are a couple of kinds of "free memory". The most common is    
          the amount of memory immediately available without reclaiming       
          memory already in use. That is the size of the free pages queue     
          plus some other reserved pages. This amount is exported by the      
          vm.stats.vm.v_free_count sysctl(8), shown, for instance, by top(1). 
          Another kind of "free memory" is the total amount of virtual memory 
          available to userland processes, which depends on the sum of swap   
          space and usable memory. Other kinds of "free memory" descriptions  
          are also possible, but it is relatively useless to define these,    
          but rather it is important to make sure that the paging rate is     
          kept low, and to avoid running out of swap space.                   
   10.23. What is /var/empty?                                                 
          /var/empty is a directory that the sshd(8) program uses when        
          performing privilege separation. The /var/empty directory is empty, 
          owned by root and has the schg flag set. This directory should not  
          be deleted.                                                         
   10.24. I just changed /etc/newsyslog.conf. How can I check if it does what 
          I expect?                                                           
          To see what newsyslog(8) will do, use the following:                
                                                                              
          % newsyslog -nrvv                                                   
   10.25. My time is wrong, how can I change the timezone?                    
          Use tzsetup(8).                                                     

              Chapter 11. The X Window System and Virtual Consoles

   11.1. What is the X Window System?

   11.2. I want to run Xorg, how do I go about it?

   11.3. I tried to run X, but I get a No devices detected. error when I type
   startx. What do I do now?

   11.4. Why does my mouse not work with X?

   11.5. My mouse has a fancy wheel. Can I use it in X?

   11.6. My laptop has a Synaptics touchpad. Can I use it in X?

   11.7. How do I use remote X displays?

   11.8. What is a virtual console and how do I make more?

   11.9. How do I access the virtual consoles from X?

   11.10. How do I start XDM on boot?

   11.11. Why do I get Couldn't open console when I run xconsole?

   11.12. Why does my PS/2 mouse misbehave under X?

   11.13. How do I reverse the mouse buttons?

   11.14. How do I install a splash screen and where do I find them?

   11.15. Can I use the Windows keys on my keyboard in X?

   11.16. How can I get 3D hardware acceleration for OpenGL(R)?

   11.1.  What is the X Window System?                                        
          The X Window System (commonly X11) is the most widely available     
          windowing system capable of running on UNIX(R) or UNIX(R) like      
          systems, including FreeBSD. The X.Org Foundation administers the X  
          protocol standards, with the current reference implementation,      
          version 11 release 7.7, so references are often shortened to X11.   
                                                                              
          Many implementations are available for different architectures and  
          operating systems. An implementation of the server-side code is     
          properly known as an X server.                                      
   11.2.  I want to run Xorg, how do I go about it?                           
          To install Xorg do one of the following:                            
                                                                              
          Use the x11/xorg meta-port, which builds and installs every Xorg    
          component.                                                          
                                                                              
          Use x11/xorg-minimal, which builds and installs only the necessary  
          Xorg components.                                                    
                                                                              
          Install Xorg from FreeBSD packages:                                 
                                                                              
          # pkg install xorg                                                  
                                                                              
          After the installation of Xorg, follow the instructions from the    
          X11 Configuration section of the FreeBSD Handbook.                  
   11.3.  I tried to run X, but I get a No devices detected. error when I     
          type startx. What do I do now?                                      
          The system is probably running at a raised securelevel. It is not   
          possible to start X at a raised securelevel because X requires      
          write access to io(4). For more information, see at the init(8)     
          manual page.                                                        
                                                                              
          There are two solutions to the problem: set the securelevel back    
          down to zero or run xdm(1) (or an alternative display manager) at   
          boot time before the securelevel is raised.                         
                                                                              
          See Q: 11.10 for more information about running xdm(1) at boot      
          time.                                                               
   11.4.  Why does my mouse not work with X?                                  
          When using vt(4), the default console driver, FreeBSD can be        
          configured to support a mouse pointer on each virtual screen. To    
          avoid conflicting with X, vt(4) supports a virtual device called    
          /dev/sysmouse. All mouse events received from the real mouse device 
          are written to the sysmouse(4) device via moused(8). To use the     
          mouse on one or more virtual consoles, and use X, see Q: 4.4.1 and  
          set up moused(8).                                                   
                                                                              
          Then edit /etc/X11/xorg.conf and make sure the following lines      
          exist:                                                              
                                                                              
          Section "InputDevice"                                               
             Option          "Protocol" "SysMouse"                            
             Option          "Device" "/dev/sysmouse"                         
          .....                                                               
                                                                              
          Starting with Xorg version 7.4, the InputDevice sections in         
          xorg.conf are ignored in favor of autodetected devices. To restore  
          the old behavior, add the following line to the ServerLayout or     
          ServerFlags section:                                                
                                                                              
          Option "AutoAddDevices" "false"                                     
                                                                              
          Some people prefer to use /dev/mouse under X. To make this work,    
          /dev/mouse should be linked to /dev/sysmouse (see sysmouse(4)) by   
          adding the following line to /etc/devfs.conf (see devfs.conf(5)):   
                                                                              
          link    sysmouse    mouse                                           
                                                                              
          This link can be created by restarting devfs(5) with the following  
          command (as root):                                                  
                                                                              
          # service devfs restart                                             
   11.5.  My mouse has a fancy wheel. Can I use it in X?                      
          Yes, if X is configured for a 5 button mouse. To do this, add the   
          lines Buttons 5 and ZAxisMapping 4 5 to the "InputDevice" section   
          of /etc/X11/xorg.conf, as seen in this example:                     
                                                                              
          Section "InputDevice"                                               
             Identifier      "Mouse1"                                         
             Driver          "mouse"                                          
             Option          "Protocol" "auto"                                
             Option          "Device" "/dev/sysmouse"                         
             Option          "Buttons" "5"                                    
             Option          "ZAxisMapping" "4 5"                             
          EndSection                                                          
                                                                              
          The mouse can be enabled in Emacs by adding these lines to          
          ~/.emacs:                                                           
                                                                              
          ;; wheel mouse                                                      
          (global-set-key [mouse-4] 'scroll-down)                             
          (global-set-key [mouse-5] 'scroll-up)                               
   11.6.  My laptop has a Synaptics touchpad. Can I use it in X?              
          Yes, after configuring a few things to make it work.                
                                                                              
          In order to use the Xorg synaptics driver, first remove             
          moused_enable from rc.conf.                                         
                                                                              
          To enable synaptics, add the following line to /boot/loader.conf:   
                                                                              
          hw.psm.synaptics_support="1"                                        
                                                                              
          Add the following to /etc/X11/xorg.conf:                            
                                                                              
          Section "InputDevice"                                               
          Identifier  "Touchpad0"                                             
          Driver      "synaptics"                                             
          Option      "Protocol" "psm"                                        
          Option      "Device" "/dev/psm0"                                    
          EndSection                                                          
                                                                              
          And be sure to add the following into the "ServerLayout" section:   
                                                                              
          InputDevice    "Touchpad0" "SendCoreEvents"                         
   11.7.  How do I use remote X displays?                                     
          For security reasons, the default setting is to not allow a machine 
          to remotely open a window.                                          
                                                                              
          To enable this feature, start X with the optional -listen_tcp       
          argument:                                                           
                                                                              
          % startx -listen_tcp                                                
   11.8.  What is a virtual console and how do I make more?                   
          Virtual consoles provide several simultaneous sessions on the same  
          machine without doing anything complicated like setting up a        
          network or running X.                                               
                                                                              
          When the system starts, it will display a login prompt on the       
          monitor after displaying all the boot messages. Type in your login  
          name and password to start working on the first virtual console.    
                                                                              
          To start another session, perhaps to look at documentation for a    
          program or to read mail while waiting for an FTP transfer to        
          finish, hold down Alt and press F2. This will display the login     
          prompt for the second virtual console. To go back to the original   
          session, press Alt+F1.                                              
                                                                              
          The default FreeBSD installation has eight virtual consoles         
          enabled. Alt+F1, Alt+F2, Alt+F3, and so on will switch between      
          these virtual consoles.                                             
                                                                              
          To enable more of virtual consoles, edit /etc/ttys (see ttys(5))    
          and add entries for ttyv8 to ttyvc, after the comment on "Virtual   
          terminals":                                                         
                                                                              
          # Edit the existing entry for ttyv8 in /etc/ttys and change         
          # "off" to "on".                                                    
          ttyv8   "/usr/libexec/getty Pc"         xterm  on secure            
          ttyv9   "/usr/libexec/getty Pc"         xterm  on secure            
          ttyva   "/usr/libexec/getty Pc"         xterm  on secure            
          ttyvb   "/usr/libexec/getty Pc"         xterm  on secure            
                                                                              
          The more virtual terminals, the more resources that are used. This  
          can be problematic on systems with 8 MB RAM or less. Consider       
          changing secure to insecure.                                        
                                                                              
            Important:                                                        
                                                                              
          In order to run an X server, at least one virtual terminal must be  
          left to off for it to use. This means that only eleven of the       
          Alt-function keys can be used as virtual consoles so that one is    
          left for the X server.                                              
                                                                              
          For example, to run X and eleven virtual consoles, the setting for  
          virtual terminal 12 should be:                                      
                                                                              
          ttyvb   "/usr/libexec/getty Pc"         xterm  off secure           
                                                                              
          The easiest way to activate the virtual consoles is to reboot.      
   11.9.  How do I access the virtual consoles from X?                        
          Use Ctrl+Alt+Fn to switch back to a virtual console. Press          
          Ctrl+Alt+F1 to return to the first virtual console.                 
                                                                              
          Once at a text console, use Alt+Fn to move between them.            
                                                                              
          To return to the X session, switch to the virtual console running   
          X. If X was started from the command line using startx, the X       
          session will attach to the next unused virtual console, not the     
          text console from which it was invoked. For eight active virtual    
          terminals, X will run on the ninth, so use Alt+F9.                  
   11.10. How do I start XDM on boot?                                         
          There are two schools of thought on how to start xdm(1). One school 
          starts xdm from /etc/ttys (see ttys(5)) using the supplied example, 
          while the other runs xdm from rc.local (see rc(8)) or from an X     
          script in /usr/local/etc/rc.d. Both are equally valid, and one may  
          work in situations where the other does not. In both cases the      
          result is the same: X will pop up a graphical login prompt.         
                                                                              
          The ttys(5) method has the advantage of documenting which vty X     
          will start on and passing the responsibility of restarting the X    
          server on logout to init(8). The rc(8) method makes it easy to kill 
          xdm if there is a problem starting the X server.                    
                                                                              
          If loaded from rc(8), xdm should be started without any arguments.  
          xdm must start after getty(8) runs, or else getty and xdm will      
          conflict, locking out the console. The best way around this is to   
          have the script sleep 10 seconds or so then launch xdm.             
                                                                              
          When starting xdm from /etc/ttys, there still is a chance of        
          conflict between xdm and getty(8). One way to avoid this is to add  
          the vt number in /usr/local/lib/X11/xdm/Xservers:                   
                                                                              
          :0 local /usr/local/bin/X vt4                                       
                                                                              
          The above example will direct the X server to run in /dev/ttyv3.    
          Note the number is offset by one. The X server counts the vty from  
          one, whereas the FreeBSD kernel numbers the vty from zero.          
   11.11. Why do I get Couldn't open console when I run xconsole?             
          When X is started with startx, the permissions on /dev/console will 
          not get changed, resulting in things like xterm -C and xconsole not 
          working.                                                            
                                                                              
          This is because of the way console permissions are set by default.  
          On a multi-user system, one does not necessarily want just any user 
          to be able to write on the system console. For users who are        
          logging directly onto a machine with a VTY, the fbtab(5) file       
          exists to solve such problems.                                      
                                                                              
          In a nutshell, make sure an uncommented line of the form is in      
          /etc/fbtab (see fbtab(5)):                                          
                                                                              
          /dev/ttyv0 0600 /dev/console                                        
                                                                              
          It will ensure that whomever logs in on /dev/ttyv0 will own the     
          console.                                                            
   11.12. Why does my PS/2 mouse misbehave under X?                           
          The mouse and the mouse driver may have become out of               
          synchronization. In rare cases, the driver may also erroneously     
          report synchronization errors:                                      
                                                                              
          psmintr: out of sync (xxxx != yyyy)                                 
                                                                              
          If this happens, disable the synchronization check code by setting  
          the driver flags for the PS/2 mouse driver to 0x100. This can be    
          easiest achieved by adding hint.psm.0.flags="0x100" to              
          /boot/loader.conf and rebooting.                                    
   11.13. How do I reverse the mouse buttons?                                 
          Type xmodmap -e "pointer = 3 2 1". Add this command to ~/.xinitrc   
          or ~/.xsession to make it happen automatically.                     
   11.14. How do I install a splash screen and where do I find them?          
          The detailed answer for this question can be found in the Boot Time 
          Splash Screens section of the FreeBSD Handbook.                     
   11.15. Can I use the Windows keys on my keyboard in X?                     
          Yes. Use xmodmap(1) to define which functions the keys should       
          perform.                                                            
                                                                              
          Assuming all Windows keyboards are standard, the keycodes for these 
          three keys are the following:                                       
                                                                              
            * 115 - Windows key, between the left-hand Ctrl and Alt keys      
                                                                              
            * 116 - Windows key, to the right of AltGr                        
                                                                              
            * 117 - Menu, to the left of the right-hand Ctrl                  
                                                                              
          To have the left Windows key print a comma, try this.               
                                                                              
          # xmodmap -e "keycode 115 = comma"                                  
                                                                              
          To have the Windows key-mappings enabled automatically every time X 
          is started, either put the xmodmap commands in ~/.xinitrc or,       
          preferably, create a ~/.xmodmaprc and include the xmodmap options,  
          one per line, then add the following line to ~/.xinitrc:            
                                                                              
          xmodmap $HOME/.xmodmaprc                                            
                                                                              
          For example, to map the 3 keys to be F13, F14, and F15,             
          respectively. This would make it easy to map them to useful         
          functions within applications or the window manager.                
                                                                              
          To do this, put the following in ~/.xmodmaprc.                      
                                                                              
          keycode 115 = F13                                                   
          keycode 116 = F14                                                   
          keycode 117 = F15                                                   
                                                                              
          For the x11-wm/fvwm2 desktop manager, one could map the keys so     
          that F13 iconifies or de-iconifies the window the cursor is in, F14 
          brings the window the cursor is in to the front or, if it is        
          already at the front, pushes it to the back, and F15 pops up the    
          main Workplace menu even if the cursor is not on the desktop, which 
          is useful when no part of the desktop is visible.                   
                                                                              
          The following entries in ~/.fvwmrc implement the aforementioned     
          setup:                                                              
                                                                              
          Key F13        FTIWS    A        Iconify                            
          Key F14        FTIWS    A        RaiseLower                         
          Key F15        A        A        Menu Workplace Nop                 
   11.16. How can I get 3D hardware acceleration for OpenGL(R)?               
          The availability of 3D acceleration depends on the version of Xorg  
          and the type of video chip. For an nVidia chip, use the binary      
          drivers provided for FreeBSD by installing one of the following     
          ports:                                                              
                                                                              
          The latest versions of nVidia cards are supported by the            
          x11/nvidia-driver port.                                             
                                                                              
          Older drivers are available as x11/nvidia-driver-###                
                                                                              
          nVidia provides detailed information on which card is supported by  
          which driver on their web site:                                     
          http://www.nvidia.com/object/IO_32667.html.                         
                                                                              
          For Matrox G200/G400, check the x11-drivers/xf86-video-mga port.    
                                                                              
          For ATI Rage 128 and Radeon see ati(4), r128(4) and radeon(4).      

                             Chapter 12. Networking

   12.1. Where can I get information on "diskless booting"?

   12.2. Can a FreeBSD box be used as a dedicated network router?

   12.3. Does FreeBSD support NAT or Masquerading?

   12.4. How can I set up Ethernet aliases?

   12.5. Why can I not NFS-mount from a Linux(R) box?

   12.6. Why does mountd keep telling me it can't change attributes and that
   I have a bad exports list on my FreeBSD NFS server?

   12.7. How do I enable IP multicast support?

   12.8. Why do I have to use the FQDN for hosts on my site?

   12.9. Why do I get an error, Permission denied, for all networking
   operations?

   12.10. Why is my ipfw "fwd" rule to redirect a service to another machine
   not working?

   12.11. How can I redirect service requests from one machine to another?

   12.12. Where can I get a bandwidth management tool?

   12.13. Why do I get /dev/bpf0: device not configured?

   12.14. How do I mount a disk from a Windows(R) machine that is on my
   network, like smbmount in Linux(R)?

   12.15. What are these messages about: Limiting icmp/open port/closed port
   response in my log files?

   12.16. What are these arp: unknown hardware address format error messages?

   12.17. Why do I keep seeing messages like: 192.168.0.10 is on fxp1 but got
   reply from 00:15:17:67:cf:82 on rl0, and how do I disable it?

   12.18. How do I compile an IPv6 only kernel?

12.1.  Where can I get information on "diskless booting"?                            
       "Diskless booting" means that the FreeBSD box is booted over a network, and   
       reads the necessary files from a server instead of its hard disk. For full    
       details, see the Handbook entry on diskless booting.                          
12.2.  Can a FreeBSD box be used as a dedicated network router?                      
       Yes. Refer to the Handbook entry on advanced networking, specifically the     
       section on routing and gateways.                                              
12.3.  Does FreeBSD support NAT or Masquerading?                                     
       Yes. For instructions on how to use NAT over a PPP connection, see the        
       Handbook entry on PPP. To use NAT over some other sort of network connection, 
       look at the natd section of the Handbook.                                     
12.4.  How can I set up Ethernet aliases?                                            
       If the alias is on the same subnet as an address already configured on the    
       interface, add netmask 0xffffffff to this command:                            
                                                                                     
       # ifconfig ed0 alias 192.0.2.2 netmask 0xffffffff                             
                                                                                     
       Otherwise, specify the network address and netmask as usual:                  
                                                                                     
       # ifconfig ed0 alias 172.16.141.5 netmask 0xffffff00                          
                                                                                     
       More information can be found in the FreeBSD Handbook.                        
12.5.  Why can I not NFS-mount from a Linux(R) box?                                  
       Some versions of the Linux(R) NFS code only accept mount requests from a      
       privileged port; try to issue the following command:                          
                                                                                     
       # mount -o -P linuxbox:/blah /mnt                                             
12.6.  Why does mountd keep telling me it can't change attributes and that I have a  
       bad exports list on my FreeBSD NFS server?                                    
       The most frequent problem is not understanding the correct format of          
       /etc/exports. Review exports(5) and the NFS entry in the Handbook, especially 
       the section on configuring NFS.                                               
12.7.  How do I enable IP multicast support?                                         
       Install the net/mrouted package or port and add mrouted_enable="YES" to       
       /etc/rc.conf start this service at boot time.                                 
12.8.  Why do I have to use the FQDN for hosts on my site?                           
       See the answer in the FreeBSD Handbook.                                       
12.9.  Why do I get an error, Permission denied, for all networking operations?      
       If the kernel is compiled with the IPFIREWALL option, be aware that the       
       default policy is to deny all packets that are not explicitly allowed.        
                                                                                     
       If the firewall is unintentionally misconfigured, restore network operability 
       by typing the following as root:                                              
                                                                                     
       # ipfw add 65534 allow all from any to any                                    
                                                                                     
       Consider setting firewall_type="open" in /etc/rc.conf.                        
                                                                                     
       For further information on configuring this firewall, see the Handbook        
       chapter.                                                                      
12.10. Why is my ipfw "fwd" rule to redirect a service to another machine not        
       working?                                                                      
       Possibly because network address translation (NAT) is needed instead of just  
       forwarding packets. A "fwd" rule only forwards packets, it does not actually  
       change the data inside the packet. Consider this rule:                        
                                                                                     
       01000 fwd 10.0.0.1 from any to foo 21                                         
                                                                                     
       When a packet with a destination address of foo arrives at the machine with   
       this rule, the packet is forwarded to 10.0.0.1, but it still has the          
       destination address of foo. The destination address of the packet is not      
       changed to 10.0.0.1. Most machines would probably drop a packet that they     
       receive with a destination address that is not their own. Therefore, using a  
       "fwd" rule does not often work the way the user expects. This behavior is a   
       feature and not a bug.                                                        
                                                                                     
       See the FAQ about redirecting services, the natd(8) manual, or one of the     
       several port redirecting utilities in the Ports Collection for a correct way  
       to do this.                                                                   
12.11. How can I redirect service requests from one machine to another?              
       FTP and other service requests can be redirected with the sysutils/socket     
       package or port. Replace the entry for the service in /etc/inetd.conf to call 
       socket, as seen in this example for ftpd:                                     
                                                                                     
       ftp stream tcp nowait nobody /usr/local/bin/socket socket ftp.example.com ftp 
                                                                                     
       where ftp.example.com and ftp are the host and port to redirect to,           
       respectively.                                                                 
12.12. Where can I get a bandwidth management tool?                                  
       There are three bandwidth management tools available for FreeBSD. dummynet(4) 
       is integrated into FreeBSD as part of ipfw(4). ALTQ has been integrated into  
       FreeBSD as part of pf(4). Bandwidth Manager from Emerging Technologies is a   
       commercial product.                                                           
12.13. Why do I get /dev/bpf0: device not configured?                                
       The running application requires the Berkeley Packet Filter (bpf(4)), but it  
       was removed from a custom kernel. Add this to the kernel config file and      
       build a new kernel:                                                           
                                                                                     
       device bpf        # Berkeley Packet Filter                                    
12.14. How do I mount a disk from a Windows(R) machine that is on my network, like   
       smbmount in Linux(R)?                                                         
       Use the SMBFS toolset. It includes a set of kernel modifications and a set of 
       userland programs. The programs and information are available as              
       mount_smbfs(8) in the base system.                                            
12.15. What are these messages about: Limiting icmp/open port/closed port response   
       in my log files?                                                              
       This kernel message indicates that some activity is provoking it to send a    
       large amount of ICMP or TCP reset (RST) responses. ICMP responses are often   
       generated as a result of attempted connections to unused UDP ports. TCP       
       resets are generated as a result of attempted connections to unopened TCP     
       ports. Among others, these are the kinds of activities which may cause these  
       messages:                                                                     
                                                                                     
         * Brute-force denial of service (DoS) attacks (as opposed to single-packet  
           attacks which exploit a specific vulnerability).                          
                                                                                     
         * Port scans which attempt to connect to a large number of ports (as        
           opposed to only trying a few well-known ports).                           
                                                                                     
       The first number in the message indicates how many packets the kernel would   
       have sent if the limit was not in place, and the second indicates the limit.  
       This limit is controlled using net.inet.icmp.icmplim. This example sets the   
       limit to 300 packets per second:                                              
                                                                                     
       # sysctl net.inet.icmp.icmplim=300                                            
                                                                                     
       To disable these messages without disabling response limiting, use            
       net.inet.icmp.icmplim_output to disable the output:                           
                                                                                     
       # sysctl net.inet.icmp.icmplim_output=0                                       
                                                                                     
       Finally, to disable response limiting completely, set net.inet.icmp.icmplim   
       to 0. Disabling response limiting is discouraged for the reasons listed       
       above.                                                                        
12.16. What are these arp: unknown hardware address format error messages?           
       This means that some device on the local Ethernet is using a MAC address in a 
       format that FreeBSD does not recognize. This is probably caused by someone    
       experimenting with an Ethernet card somewhere else on the network. This is    
       most commonly seen on cable modem networks. It is harmless, and should not    
       affect the performance of the FreeBSD system.                                 
12.17. Why do I keep seeing messages like: 192.168.0.10 is on fxp1 but got reply     
       from 00:15:17:67:cf:82 on rl0, and how do I disable it?                       
       A packet is coming from outside the network unexpectedly. To disable them,    
       set net.link.ether.inet.log_arp_wrong_iface to 0.                             
12.18. How do I compile an IPv6 only kernel?                                         
       Configure your kernel with these settings:                                    
                                                                                     
       include GENERIC                                                               
       ident GENERIC-IPV6ONLY                                                        
       makeoptions MKMODULESENV+="WITHOUT_INET_SUPPORT="                             
       nooptions INET                                                                
       nodevice gre                                                                  

                              Chapter 13. Security

   13.1. What is a sandbox?

   13.2. What is securelevel?

   13.3. What is this UID 0 toor account? Have I been compromised?

   13.1. What is a sandbox?                                                   
         "Sandbox" is a security term. It can mean two things:                
                                                                              
           * A process which is placed inside a set of virtual walls that are 
             designed to prevent someone who breaks into the process from     
             being able to break into the wider system.                       
                                                                              
             The process is only able to run inside the walls. Since nothing  
             the process does in regards to executing code is supposed to be  
             able to breach the walls, a detailed audit of its code is not    
             needed in order to be able to say certain things about its       
             security.                                                        
                                                                              
             The walls might be a user ID, for example. This is the           
             definition used in the security(7) and named(8) man pages.       
                                                                              
             Take the ntalk service, for example (see inetd(8)). This service 
             used to run as user ID root. Now it runs as user ID tty. The tty 
             user is a sandbox designed to make it more difficult for someone 
             who has successfully hacked into the system via ntalk from being 
             able to hack beyond that user ID.                                
                                                                              
           * A process which is placed inside a simulation of the machine. It 
             means that someone who is able to break into the process may     
             believe that he can break into the wider machine but is, in      
             fact, only breaking into a simulation of that machine and not    
             modifying any real data.                                         
                                                                              
             The most common way to accomplish this is to build a simulated   
             environment in a subdirectory and then run the processes in that 
             directory chrooted so that / for that process is this directory, 
             not the real / of the system).                                   
                                                                              
             Another common use is to mount an underlying file system         
             read-only and then create a file system layer on top of it that  
             gives a process a seemingly writeable view into that file        
             system. The process may believe it is able to write to those     
             files, but only the process sees the effects - other processes   
             in the system do not, necessarily.                               
                                                                              
             An attempt is made to make this sort of sandbox so transparent   
             that the user (or hacker) does not realize that he is sitting in 
             it.                                                              
                                                                              
         UNIX(R) implements two core sandboxes. One is at the process level,  
         and one is at the userid level.                                      
                                                                              
         Every UNIX(R) process is completely firewalled off from every other  
         UNIX(R) process. One process cannot modify the address space of      
         another.                                                             
                                                                              
         A UNIX(R) process is owned by a particular userid. If the user ID is 
         not the root user, it serves to firewall the process off from        
         processes owned by other users. The user ID is also used to firewall 
         off on-disk data.                                                    
   13.2. What is securelevel?                                                 
         securelevel is a security mechanism implemented in the kernel. When  
         the securelevel is positive, the kernel restricts certain tasks; not 
         even the superuser (root) is allowed to do them. The securelevel     
         mechanism limits the ability to:                                     
                                                                              
           * Unset certain file flags, such as schg (the system immutable     
             flag).                                                           
                                                                              
           * Write to kernel memory via /dev/mem and /dev/kmem.               
                                                                              
           * Load kernel modules.                                             
                                                                              
           * Alter firewall rules.                                            
                                                                              
         To check the status of the securelevel on a running system:          
                                                                              
         # sysctl -n kern.securelevel                                         
                                                                              
         The output contains the current value of the securelevel. If it is   
         greater than 0, at least some of the securelevel's protections are   
         enabled.                                                             
                                                                              
         The securelevel of a running system cannot be lowered as this would  
         defeat its purpose. If a task requires that the securelevel be       
         non-positive, change the kern_securelevel and                        
         kern_securelevel_enable variables in /etc/rc.conf and reboot.        
                                                                              
         For more information on securelevel and the specific things all the  
         levels do, consult init(8).                                          
                                                                              
           Warning:                                                           
                                                                              
         Securelevel is not a silver bullet; it has many known deficiencies.  
         More often than not, it provides a false sense of security.          
                                                                              
         One of its biggest problems is that in order for it to be at all     
         effective, all files used in the boot process up until the           
         securelevel is set must be protected. If an attacker can get the     
         system to execute their code prior to the securelevel being set      
         (which happens quite late in the boot process since some things the  
         system must do at start-up cannot be done at an elevated             
         securelevel), its protections are invalidated. While this task of    
         protecting all files used in the boot process is not technically     
         impossible, if it is achieved, system maintenance will become a      
         nightmare since one would have to take the system down, at least to  
         single-user mode, to modify a configuration file.                    
                                                                              
         This point and others are often discussed on the mailing lists,      
         particularly the FreeBSD security mailing list. Search the archives  
         here for an extensive discussion. A more fine-grained mechanism is   
         preferred.                                                           
   13.3. What is this UID 0 toor account? Have I been compromised?            
         Do not worry. toor is an "alternative" superuser account, where toor 
         is root spelled backwards. It is intended to be used with a          
         non-standard shell so the default shell for root does not need to    
         change. This is important as shells which are not part of the base   
         distribution, but are instead installed from ports or packages, are  
         installed in /usr/local/bin which, by default, resides on a          
         different file system. If root's shell is located in /usr/local/bin  
         and the file system containing /usr/local/bin) is not mounted, root  
         will not be able to log in to fix a problem and will have to reboot  
         into single-user mode in order to enter the path to a shell.         
                                                                              
         Some people use toor for day-to-day root tasks with a non-standard   
         shell, leaving root, with a standard shell, for single-user mode or  
         emergencies. By default, a user cannot log in using toor as it does  
         not have a password, so log in as root and set a password for toor   
         before using it to login.                                            

                       Chapter 14. Serial Communications

   This section answers common questions about serial communications with
   FreeBSD.

   14.1. How do I get the boot: prompt to show on the serial console?

   14.2. How do I tell if FreeBSD found my serial ports or modem cards?

   14.3. How do I access the serial ports on FreeBSD? (x86-specific)

   14.4. How do I enable support for a multi-port serial card?

   14.5. Can I set the default serial parameters for a port?

   14.6. Why can I not run tip or cu?

14.1. How do I get the boot: prompt to show on the serial console?                  
      See this section of the Handbook.                                             
14.2. How do I tell if FreeBSD found my serial ports or modem cards?                
      As the FreeBSD kernel boots, it will probe for the serial ports for which the 
      kernel is configured. Either watch the boot messages closely or run this      
      command after the system is up and running:                                   
                                                                                    
      % grep -E '^(sio|uart)[0-9]' < /var/run/dmesg.boot                            
      sio0: <16550A-compatible COM port> port 0x3f8-0x3ff irq 4 flags 0x10 on acpi0 
      sio0: type 16550A                                                             
      sio1: <16550A-compatible COM port> port 0x2f8-0x2ff irq 3 on acpi0            
      sio1: type 16550A                                                             
                                                                                    
      This example shows two serial ports. The first is on IRQ4, port address       
      0x3f8, and has a 16550A-type UART chip. The second uses the same kind of chip 
      but is on IRQ3 and is at port address 0x2f8. Internal modem cards are treated 
      just like serial ports, except that they always have a modem attached to the  
      port.                                                                         
                                                                                    
      The GENERIC kernel includes support for two serial ports using the same IRQ   
      and port address settings in the above example. If these settings are not     
      right for the system, or if there are more modem cards or serial ports than   
      the kernel is configured for, reconfigure using the instructions in building  
      a kernel for more details.                                                    
14.3. How do I access the serial ports on FreeBSD? (x86-specific)                   
      The third serial port, sio2, or COM3, is on /dev/cuad2 for dial-out devices,  
      and on /dev/ttyd2 for dial-in devices. What is the difference between these   
      two classes of devices?                                                       
                                                                                    
      When opening /dev/ttydX in blocking mode, a process will wait for the         
      corresponding cuadX device to become inactive, and then wait for the carrier  
      detect line to go active. When the cuadX device is opened, it makes sure the  
      serial port is not already in use by the ttydX device. If the port is         
      available, it steals it from the ttydX device. Also, the cuadX device does    
      not care about carrier detect. With this scheme and an auto-answer modem,     
      remote users can log in and local users can still dial out with the same      
      modem and the system will take care of all the conflicts.                     
14.4. How do I enable support for a multi-port serial card?                         
      The section on kernel configuration provides information about configuring    
      the kernel. For a multi-port serial card, place an sio(4) line for each       
      serial port on the card in the device.hints(5) file. But place the IRQ        
      specifiers on only one of the entries. All of the ports on the card should    
      share one IRQ. For consistency, use the last serial port to specify the IRQ.  
      Also, specify the following option in the kernel configuration file:          
                                                                                    
      options COM_MULTIPORT                                                         
                                                                                    
      The following /boot/device.hints example is for an AST 4-port serial card on  
      IRQ 12:                                                                       
                                                                                    
      hint.sio.4.at="isa"                                                           
      hint.sio.4.port="0x2a0"                                                       
      hint.sio.4.flags="0x701"                                                      
      hint.sio.5.at="isa"                                                           
      hint.sio.5.port="0x2a8"                                                       
      hint.sio.5.flags="0x701"                                                      
      hint.sio.6.at="isa"                                                           
      hint.sio.6.port="0x2b0"                                                       
      hint.sio.6.flags="0x701"                                                      
      hint.sio.7.at="isa"                                                           
      hint.sio.7.port="0x2b8"                                                       
      hint.sio.7.flags="0x701"                                                      
      hint.sio.7.irq="12"                                                           
                                                                                    
      The flags indicate that the master port has minor number 7 (0x700), and all   
      the ports share an IRQ (0x001).                                               
14.5. Can I set the default serial parameters for a port?                           
      See the Serial Communications section in the FreeBSD Handbook.                
14.6. Why can I not run tip or cu?                                                  
      The built-in tip(1) and cu(1) utilities can only access the /var/spool/lock   
      directory via user uucp and group dialer. Use the dialer group to control who 
      has access to the modem or remote systems by adding user accounts to dialer.  
                                                                                    
      Alternatively, everyone can be configured to run tip(1) and cu(1) by typing:  
                                                                                    
      # chmod 4511 /usr/bin/cu                                                      
      # chmod 4511 /usr/bin/tip                                                     

                      Chapter 15. Miscellaneous Questions

   15.1. FreeBSD uses a lot of swap space even when the computer has free
   memory left. Why?

   15.2. Why does top show very little free memory even when I have very few
   programs running?

   15.3. Why will chmod not change the permissions on symlinks?

   15.4. Can I run DOS binaries under FreeBSD?

   15.5. What do I need to do to translate a FreeBSD document into my native
   language?

   15.6. Why does my email to any address at FreeBSD.org bounce?

   15.7. Where can I find a free FreeBSD account?

   15.8. What is the cute little red guy's name?

   15.9. Can I use the BSD daemon image?

   15.10. Do you have any BSD daemon images I could use?

   15.11. I have seen an acronym or other term on the mailing lists and I do
   not understand what it means. Where should I look?

   15.12. Why should I care what color the bikeshed is?

   15.1.  FreeBSD uses a lot of swap space even when the computer has free    
          memory left. Why?                                                   
          FreeBSD will proactively move entirely idle, unused pages of main   
          memory into swap in order to make more main memory available for    
          active use. This heavy use of swap is balanced by using the extra   
          free memory for caching.                                            
                                                                              
          Note that while FreeBSD is proactive in this regard, it does not    
          arbitrarily decide to swap pages when the system is truly idle.     
          Thus, the system will not be all paged out after leaving it idle    
          overnight.                                                          
   15.2.  Why does top show very little free memory even when I have very few 
          programs running?                                                   
          The simple answer is that free memory is wasted memory. Any memory  
          that programs do not actively allocate is used within the FreeBSD   
          kernel as disk cache. The values shown by top(1) labeled as Inact   
          and Laundry are cached data at different aging levels. This cached  
          data means the system does not have to access a slow disk again for 
          data it has accessed recently, thus increasing overall performance. 
          In general, a low value shown for Free memory in top(1) is good,    
          provided it is not very low.                                        
   15.3.  Why will chmod not change the permissions on symlinks?              
          Symlinks do not have permissions, and by default, chmod(1) will     
          follow symlinks to change the permissions on the source file, if    
          possible. For the file, foo with a symlink named bar, this command  
          will always succeed.                                                
                                                                              
          % chmod g-w bar                                                     
                                                                              
          However, the permissions on bar will not have changed.              
                                                                              
          When changing modes of the file hierarchies rooted in the files     
          instead of the files themselves, use either -H or -L together with  
          -R to make this work. See chmod(1) and symlink(7) for more          
          information.                                                        
                                                                              
            Warning:                                                          
                                                                              
          -R does a recursive chmod(1). Be careful about specifying           
          directories or symlinks to directories to chmod(1). To change the   
          permissions of a directory referenced by a symlink, use chmod(1)    
          without any options and follow the symlink with a trailing slash    
          (/). For example, if foo is a symlink to directory bar, to change   
          the permissions of foo (actually bar), do something like:           
                                                                              
          % chmod 555 foo/                                                    
                                                                              
          With the trailing slash, chmod(1) will follow the symlink, foo, to  
          change the permissions of the directory, bar.                       
   15.4.  Can I run DOS binaries under FreeBSD?                               
          Yes. A DOS emulation program, emulators/doscmd, is available in the 
          FreeBSD Ports Collection.                                           
                                                                              
          If doscmd will not suffice, emulators/pcemu emulates an 8088 and    
          enough BIOS services to run many DOS text-mode applications. It     
          requires the X Window System.                                       
                                                                              
          The Ports Collection also has emulators/dosbox. The main focus of   
          this application is emulating old DOS games using the local file    
          system for files.                                                   
   15.5.  What do I need to do to translate a FreeBSD document into my native 
          language?                                                           
          See the Translation FAQ in the FreeBSD Documentation Project        
          Primer.                                                             
   15.6.  Why does my email to any address at FreeBSD.org bounce?             
          The FreeBSD.org mail system implements some Postfix checks on       
          incoming mail and rejects mail that is either from misconfigured    
          relays or otherwise appears likely to be spam. Some of the specific 
          requirements are:                                                   
                                                                              
            * The IP address of the SMTP client must "reverse-resolve" to a   
              forward confirmed hostname.                                     
                                                                              
            * The fully-qualified hostname given in the SMTP conversation     
              (either HELO or EHLO) must resolve to the IP address of the     
              client.                                                         
                                                                              
          Other advice to help mail reach its destination include:            
                                                                              
            * Mail should be sent in plain text, and messages sent to mailing 
              lists should generally be no more than 200KB in length.         
                                                                              
            * Avoid excessive cross posting. Choose one mailing list which    
              seems most relevant and send it there.                          
                                                                              
          If you still have trouble with email infrastructure at FreeBSD.org, 
          send a note with the details to <postmaster@freebsd.org>; Include a 
          date/time interval so that logs may be reviewed - and note that we  
          only keep one week's worth of mail logs. (Be sure to specify the    
          time zone or offset from UTC.)                                      
   15.7.  Where can I find a free FreeBSD account?                            
          While FreeBSD does not provide open access to any of their servers, 
          others do provide open access UNIX(R) systems. The charge varies    
          and limited services may be available.                              
                                                                              
          Arbornet, Inc, also known as M-Net, has been providing open access  
          to UNIX(R) systems since 1983. Starting on an Altos running System  
          III, the site switched to BSD/OS in 1991. In June of 2000, the site 
          switched again to FreeBSD. M-Net can be accessed via telnet and SSH 
          and provides basic access to the entire FreeBSD software suite.     
          However, network access is limited to members and patrons who       
          donate to the system, which is run as a non-profit organization.    
          M-Net also provides an bulletin board system and interactive chat.  
   15.8.  What is the cute little red guy's name?                             
          He does not have one, and is just called "the BSD daemon". If you   
          insist upon using a name, call him "beastie". Note that "beastie"   
          is pronounced "BSD".                                                
                                                                              
          More about the BSD daemon is available on his home page.            
   15.9.  Can I use the BSD daemon image?                                     
          Perhaps. The BSD daemon is copyrighted by Marshall Kirk McKusick.   
          Check his Statement on the Use of the BSD Daemon Figure for         
          detailed usage terms.                                               
                                                                              
          In summary, the image can be used in a tasteful manner, for         
          personal use, so long as appropriate credit is given. Before using  
          the logo commercially, contact Kirk McKusick <mckusick@FreeBSD.org> 
          for permission. More details are available on the BSD Daemon's home 
          page.                                                               
   15.10. Do you have any BSD daemon images I could use?                      
          Xfig and eps drawings are available under                           
          /usr/share/examples/BSD_daemon/.                                    
   15.11. I have seen an acronym or other term on the mailing lists and I do  
          not understand what it means. Where should I look?                  
          Refer to the FreeBSD Glossary.                                      
   15.12. Why should I care what color the bikeshed is?                       
          The really, really short answer is that you should not. The         
          somewhat longer answer is that just because you are capable of      
          building a bikeshed does not mean you should stop others from       
          building one just because you do not like the color they plan to    
          paint it. This is a metaphor indicating that you need not argue     
          about every little feature just because you know enough to do so.   
          Some people have commented that the amount of noise generated by a  
          change is inversely proportional to the complexity of the change.   
                                                                              
          The longer and more complete answer is that after a very long       
          argument about whether sleep(1) should take fractional second       
          arguments, Poul-Henning Kamp <phk@FreeBSD.org> posted a long        
          message entitled "A bike shed (any color will do) on greener        
          grass...". The appropriate portions of that message are quoted      
          below.                                                              
                                                                              
            "What is it about this bike shed?" Some of you have asked me.     
                                                                              
            It is a long story, or rather it is an old story, but it is       
            quite short actually. C. Northcote Parkinson wrote a book in      
            the early 1960s, called "Parkinson's Law", which contains a lot   
            of insight into the dynamics of management.                       
                                                                              
            [snip a bit of commentary on the book]                            
                                                                              
            In the specific example involving the bike shed, the other        
            vital component is an atomic power-plant, I guess that            
            illustrates the age of the book.                                  
                                                                              
            Parkinson shows how you can go into the board of directors and    
            get approval for building a multi-million or even billion         
            dollar atomic power plant, but if you want to build a bike shed   
            you will be tangled up in endless discussions.                    
                                                                              
            Parkinson explains that this is because an atomic plant is so     
            vast, so expensive and so complicated that people cannot grasp    
            it, and rather than try, they fall back on the assumption that    
            somebody else checked all the details before it got this far.     
            Richard P. Feynmann gives a couple of interesting, and very       
            much to the point, examples relating to Los Alamos in his         
            books.                                                            
                                                                              
            A bike shed on the other hand. Anyone can build one of those      
            over a weekend, and still have time to watch the game on TV. So   
            no matter how well prepared, no matter how reasonable you are     
            with your proposal, somebody will seize the chance to show that   
            he is doing his job, that he is paying attention, that he is      
            here.                                                             
                                                                              
            In Denmark we call it "setting your fingerprint". It is about     
            personal pride and prestige, it is about being able to point      
            somewhere and say "There! I did that." It is a strong trait in    
            politicians, but present in most people given the chance. Just    
            think about footsteps in wet cement.                              
            --Poul-Henning Kamp <phk@FreeBSD.org> on freebsd-hackers, October 
                                                                      2, 1999 

                        Chapter 16. The FreeBSD Funnies

   16.1. How cool is FreeBSD?

   16.2. Who is scratching in my memory banks??

   16.3. How many FreeBSD hackers does it take to change a lightbulb?

   16.4. Where does data written to /dev/null go?

   16.5. My colleague sits at the computer too much, how can I prank her?

   16.1. How cool is FreeBSD?                                                 
         Q. Has anyone done any temperature testing while running FreeBSD? I  
         know Linux(R) runs cooler than DOS, but have never seen a mention of 
         FreeBSD. It seems to run really hot.                                 
                                                                              
         A. No, but we have done numerous taste tests on blindfolded          
         volunteers who have also had 250 micrograms of LSD-25 administered   
         beforehand. 35% of the volunteers said that FreeBSD tasted sort of   
         orange, whereas Linux(R) tasted like purple haze. Neither group      
         mentioned any significant variances in temperature. We eventually    
         had to throw the results of this survey out entirely anyway when we  
         found that too many volunteers were wandering out of the room during 
         the tests, thus skewing the results. We think most of the volunteers 
         are at Apple now, working on their new "scratch and sniff" GUI. It   
         is a funny old business we are in!                                   
                                                                              
         Seriously, FreeBSD uses the HLT (halt) instruction when the system   
         is idle thus lowering its energy consumption and therefore the heat  
         it generates. Also if you have ACPI (Advanced Configuration and      
         Power Interface) configured, then FreeBSD can also put the CPU into  
         a low power mode.                                                    
   16.2. Who is scratching in my memory banks??                               
         Q. Is there anything "odd" that FreeBSD does when compiling the      
         kernel which would cause the memory to make a scratchy sound? When   
         compiling (and for a brief moment after recognizing the floppy drive 
         upon startup, as well), a strange scratchy sound emanates from what  
         appears to be the memory banks.                                      
                                                                              
         A. Yes! You will see frequent references to "daemons" in the BSD     
         documentation, and what most people do not know is that this refers  
         to genuine, non-corporeal entities that now possess your computer.   
         The scratchy sound coming from your memory is actually high-pitched  
         whispering exchanged among the daemons as they best decide how to    
         deal with various system administration tasks.                       
                                                                              
         If the noise gets to you, a good fdisk /mbr from DOS will get rid of 
         them, but do not be surprised if they react adversely and try to     
         stop you. In fact, if at any point during the exercise you hear the  
         satanic voice of Bill Gates coming from the built-in speaker, take   
         off running and do not ever look back! Freed from the                
         counterbalancing influence of the BSD daemons, the twin demons of    
         DOS and Windows(R) are often able to re-assert total control over    
         your machine to the eternal damnation of your soul. Now that you     
         know, given a choice you would probably prefer to get used to the    
         scratchy noises, no?                                                 
   16.3. How many FreeBSD hackers does it take to change a lightbulb?         
         One thousand, one hundred and sixty-nine:                            
                                                                              
         Twenty-three to complain to -CURRENT about the lights being out;     
                                                                              
         Four to claim that it is a configuration problem, and that such      
         matters really belong on -questions;                                 
                                                                              
         Three to submit PRs about it, one of which is misfiled under doc and 
         consists only of "it's dark";                                        
                                                                              
         One to commit an untested lightbulb which breaks buildworld, then    
         back it out five minutes later;                                      
                                                                              
         Eight to flame the PR originators for not including patches in their 
         PRs;                                                                 
                                                                              
         Five to complain about buildworld being broken;                      
                                                                              
         Thirty-one to answer that it works for them, and they must have      
         updated at a bad time;                                               
                                                                              
         One to post a patch for a new lightbulb to -hackers;                 
                                                                              
         One to complain that he had patches for this three years ago, but    
         when he sent them to -CURRENT they were just ignored, and he has had 
         bad experiences with the PR system; besides, the proposed new        
         lightbulb is non-reflexive;                                          
                                                                              
         Thirty-seven to scream that lightbulbs do not belong in the base     
         system, that committers have no right to do things like this without 
         consulting the Community, and WHAT IS -CORE DOING ABOUT IT!?         
                                                                              
         Two hundred to complain about the color of the bicycle shed;         
                                                                              
         Three to point out that the patch breaks style(9);                   
                                                                              
         Seventeen to complain that the proposed new lightbulb is under GPL;  
                                                                              
         Five hundred and eighty-six to engage in a flame war about the       
         comparative advantages of the GPL, the BSD license, the MIT license, 
         the NPL, and the personal hygiene of unnamed FSF founders;           
                                                                              
         Seven to move various portions of the thread to -chat and -advocacy; 
                                                                              
         One to commit the suggested lightbulb, even though it shines dimmer  
         than the old one;                                                    
                                                                              
         Two to back it out with a furious flame of a commit message, arguing 
         that FreeBSD is better off in the dark than with a dim lightbulb;    
                                                                              
         Forty-six to argue vociferously about the backing out of the dim     
         lightbulb and demanding a statement from -core;                      
                                                                              
         Eleven to request a smaller lightbulb so it will fit their           
         Tamagotchi if we ever decide to port FreeBSD to that platform;       
                                                                              
         Seventy-three to complain about the SNR on -hackers and -chat and    
         unsubscribe in protest;                                              
                                                                              
         Thirteen to post "unsubscribe", "How do I unsubscribe?", or "Please  
         remove me from the list", followed by the usual footer;              
                                                                              
         One to commit a working lightbulb while everybody is too busy        
         flaming everybody else to notice;                                    
                                                                              
         Thirty-one to point out that the new lightbulb would shine 0.364%    
         brighter if compiled with TenDRA (although it will have to be        
         reshaped into a cube), and that FreeBSD should therefore switch to   
         TenDRA instead of GCC;                                               
                                                                              
         One to complain that the new lightbulb lacks fairings;               
                                                                              
         Nine (including the PR originators) to ask "what is MFC?";           
                                                                              
         Fifty-seven to complain about the lights being out two weeks after   
         the bulb has been changed.                                           
                                                                              
         Nik Clayton <nik@FreeBSD.org> adds:                                  
                                                                              
         I was laughing quite hard at this.                                   
                                                                              
         And then I thought, "Hang on, shouldn't there be '1 to document it.' 
         in that list somewhere?"                                             
                                                                              
         And then I was enlightened :-)                                       
                                                                              
         Thomas Abthorpe <tabthorpe@FreeBSD.org> says: "None, real FreeBSD    
         hackers are not afraid of the dark!"                                 
   16.4. Where does data written to /dev/null go?                             
         It goes into a special data sink in the CPU where it is converted to 
         heat which is vented through the heatsink / fan assembly. This is    
         why CPU cooling is increasingly important; as people get used to     
         faster processors, they become careless with their data and more and 
         more of it ends up in /dev/null, overheating their CPUs. If you      
         delete /dev/null (which effectively disables the CPU data sink) your 
         CPU may run cooler but your system will quickly become constipated   
         with all that excess data and start to behave erratically. If you    
         have a fast network connection you can cool down your CPU by reading 
         data out of /dev/random and sending it off somewhere; however you    
         run the risk of overheating your network connection and / or         
         angering your ISP, as most of the data will end up getting converted 
         to heat by their equipment, but they generally have good cooling, so 
         if you do not overdo it you should be OK.                            
                                                                              
         Paul Robinson adds:                                                  
                                                                              
         There are other methods. As every good sysadmin knows, it is part of 
         standard practice to send data to the screen of interesting variety  
         to keep all the pixies that make up your picture happy. Screen       
         pixies (commonly mis-typed or re-named as "pixels") are categorized  
         by the type of hat they wear (red, green or blue) and will hide or   
         appear (thereby showing the color of their hat) whenever they        
         receive a little piece of food. Video cards turn data into           
         pixie-food, and then send them to the pixies - the more expensive    
         the card, the better the food, so the better behaved the pixies are. 
         They also need constant stimulation - this is why screen savers      
         exist.                                                               
                                                                              
         To take your suggestions further, you could just throw the random    
         data to console, thereby letting the pixies consume it. This causes  
         no heat to be produced at all, keeps the pixies happy and gets rid   
         of your data quite quickly, even if it does make things look a bit   
         messy on your screen.                                                
                                                                              
         Incidentally, as an ex-admin of a large ISP who experienced many     
         problems attempting to maintain a stable temperature in a server     
         room, I would strongly discourage people sending the data they do    
         not want out to the network. The fairies who do the packet switching 
         and routing get annoyed by it as well.                               
   16.5. My colleague sits at the computer too much, how can I prank her?     
         Install games/sl and wait for her to mistype sl for ls.              

                          Chapter 17. Advanced Topics

   17.1. How can I learn more about FreeBSD's internals?

   17.2. How can I contribute to FreeBSD? What can I do to help?

   17.3. What are snapshots and releases?

   17.4. How can I make the most of the data I see when my kernel panics?

   17.5. Why has dlsym() stopped working for ELF executables?

   17.6. How can I increase or reduce the kernel address space on i386?

17.1. How can I learn more about FreeBSD's internals?                             
      See the FreeBSD Architecture Handbook.                                      
                                                                                  
      Additionally, much general UNIX(R) knowledge is directly applicable to      
      FreeBSD.                                                                    
17.2. How can I contribute to FreeBSD? What can I do to help?                     
      We accept all types of contributions: documentation, code, and even art.    
      See the article on Contributing to FreeBSD for specific advice on how to do 
      this.                                                                       
                                                                                  
      And thanks for the thought!                                                 
17.3. What are snapshots and releases?                                            
      There are currently 3 active/semi-active branches in the FreeBSD Subversion 
      Repository. (Earlier branches are only changed very rarely, which is why    
      there are only 3 active branches of development):                           
                                                                                  
        * stable/11/ AKA 11-STABLE                                                
                                                                                  
        * stable/12/ AKA 12-STABLE                                                
                                                                                  
        * head/ AKA -CURRENT AKA 13-CURRENT                                       
                                                                                  
      HEAD is not an actual branch tag. It is a symbolic constant for the         
      current, non-branched development stream known as -CURRENT.                 
                                                                                  
      Right now, -CURRENT is the 13.X development stream; the 12-STABLE branch,   
      stable/12/, forked off from -CURRENT in December 2018 and the 11-STABLE     
      branch, stable/11/, forked off from -CURRENT in October 2016.               
17.4. How can I make the most of the data I see when my kernel panics?            
      Here is typical kernel panic:                                               
                                                                                  
      Fatal trap 12: page fault while in kernel mode                              
      fault virtual address   = 0x40                                              
      fault code              = supervisor read, page not present                 
      instruction pointer     = 0x8:0xf014a7e5                                    
      stack pointer           = 0x10:0xf4ed6f24                                   
      frame pointer           = 0x10:0xf4ed6f28                                   
      code segment            = base 0x0, limit 0xfffff, type 0x1b                
                              = DPL 0, pres 1, def32 1, gran 1                    
      processor eflags        = interrupt enabled, resume, IOPL = 0               
      current process         = 80 (mount)                                        
      interrupt mask          =                                                   
      trap number             = 12                                                
      panic: page fault                                                           
                                                                                  
      This message is not enough. While the instruction pointer value is          
      important, it is also configuration dependent as it varies depending on the 
      kernel image. If it is a GENERIC kernel image from one of the snapshots, it 
      is possible for somebody else to track down the offending function, but for 
      a custom kernel, only you can tell us where the fault occurred.             
                                                                                  
      To proceed:                                                                 
                                                                                  
       1. Write down the instruction pointer value. Note that the 0x8: part at    
          the beginning is not significant in this case: it is the 0xf0xxxxxx     
          part that we want.                                                      
                                                                                  
       2. When the system reboots, do the following:                              
                                                                                  
       % nm -n kernel.that.caused.the.panic | grep f0xxxxxx                       
                                                                                  
          where f0xxxxxx is the instruction pointer value. The odds are you will  
          not get an exact match since the symbols in the kernel symbol table are 
          for the entry points of functions and the instruction pointer address   
          will be somewhere inside a function, not at the start. If you do not    
          get an exact match, omit the last digit from the instruction pointer    
          value and try again:                                                    
                                                                                  
       % nm -n kernel.that.caused.the.panic | grep f0xxxxx                        
                                                                                  
          If that does not yield any results, chop off another digit. Repeat      
          until there is some sort of output. The result will be a possible list  
          of functions which caused the panic. This is a less than exact          
          mechanism for tracking down the point of failure, but it is better than 
          nothing.                                                                
                                                                                  
      However, the best way to track down the cause of a panic is by capturing a  
      crash dump, then using kgdb(1) to generate a stack trace on the crash dump. 
                                                                                  
      In any case, the method is this:                                            
                                                                                  
       1. Make sure that the following line is included in the kernel             
          configuration file:                                                     
                                                                                  
       makeoptions     DEBUG=-g          # Build kernel with gdb(1) debug symbols 
                                                                                  
       2. Change to the /usr/src directory:                                       
                                                                                  
       # cd /usr/src                                                              
                                                                                  
       3. Compile the kernel:                                                     
                                                                                  
       # make buildkernel KERNCONF=MYKERNEL                                       
                                                                                  
       4. Wait for make(1) to finish compiling.                                   
                                                                                  
       5. # make installkernel KERNCONF=MYKERNEL                                  
                                                                                  
       6. Reboot.                                                                 
                                                                                  
        Note:                                                                     
                                                                                  
      If KERNCONF is not included, the GENERIC kernel will instead be built and   
      installed.                                                                  
                                                                                  
      The make(1) process will have built two kernels.                            
      /usr/obj/usr/src/sys/MYKERNEL/kernel and                                    
      /usr/obj/usr/src/sys/MYKERNEL/kernel.debug. kernel was installed as         
      /boot/kernel/kernel, while kernel.debug can be used as the source of        
      debugging symbols for kgdb(1).                                              
                                                                                  
      To capture a crash dump, edit /etc/rc.conf and set dumpdev to point to      
      either the swap partition or AUTO. This will cause the rc(8) scripts to use 
      the dumpon(8) command to enable crash dumps. This command can also be run   
      manually. After a panic, the crash dump can be recovered using savecore(8); 
      if dumpdev is set in /etc/rc.conf, the rc(8) scripts will run savecore(8)   
      automatically and put the crash dump in /var/crash.                         
                                                                                  
        Note:                                                                     
                                                                                  
      FreeBSD crash dumps are usually the same size as physical RAM. Therefore,   
      make sure there is enough space in /var/crash to hold the dump.             
      Alternatively, run savecore(8) manually and have it recover the crash dump  
      to another directory with more room. It is possible to limit the size of    
      the crash dump by using options MAXMEM=N where N is the size of kernel's    
      memory usage in KBs. For example, for 1 GB of RAM, limit the kernel's       
      memory usage to 128 MB, so that the crash dump size will be 128 MB instead  
      of 1 GB.                                                                    
                                                                                  
      Once the crash dump has been recovered , get a stack trace as follows:      
                                                                                  
      % kgdb /usr/obj/usr/src/sys/MYKERNEL/kernel.debug /var/crash/vmcore.0       
      (kgdb) backtrace                                                            
                                                                                  
      Note that there may be several screens worth of information. Ideally, use   
      script(1) to capture all of them. Using the unstripped kernel image with    
      all the debug symbols should show the exact line of kernel source code      
      where the panic occurred. The stack trace is usually read from the bottom   
      up to trace the exact sequence of events that lead to the crash. kgdb(1)    
      can also be used to print out the contents of various variables or          
      structures to examine the system state at the time of the crash.            
                                                                                  
        Tip:                                                                      
                                                                                  
      If a second computer is available, kgdb(1) can be configured to do remote   
      debugging, including setting breakpoints and single-stepping through the    
      kernel code.                                                                
                                                                                  
        Note:                                                                     
                                                                                  
      If DDB is enabled and the kernel drops into the debugger, a panic and a     
      crash dump can be forced by typing panic at the ddb prompt. It may stop in  
      the debugger again during the panic phase. If it does, type continue and it 
      will finish the crash dump.                                                 
17.5. Why has dlsym() stopped working for ELF executables?                        
      The ELF toolchain does not, by default, make the symbols defined in an      
      executable visible to the dynamic linker. Consequently dlsym() searches on  
      handles obtained from calls to dlopen(NULL, flags) will fail to find such   
      symbols.                                                                    
                                                                                  
      To search, using dlsym(), for symbols present in the main executable of a   
      process, link the executable using the --export-dynamic option to the ELF   
      linker (ld(1)).                                                             
17.6. How can I increase or reduce the kernel address space on i386?              
      By default, the kernel address space is 1 GB (2 GB for PAE) for i386. When  
      running a network-intensive server or using ZFS, this will probably not be  
      enough.                                                                     
                                                                                  
      Add the following line to the kernel configuration file to increase         
      available space and rebuild the kernel:                                     
                                                                                  
      options KVA_PAGES=N                                                         
                                                                                  
      To find the correct value of N, divide the desired address space size (in   
      megabytes) by four. (For example, it is 512 for 2 GB.)                      

                          Chapter 18. Acknowledgments

   This innocent little Frequently Asked Questions document has been written,
   rewritten, edited, folded, spindled, mutilated, eviscerated, contemplated,
   discombobulated, cogitated, regurgitated, rebuilt, castigated, and
   reinvigorated over the last decade, by a cast of hundreds if not
   thousands. Repeatedly.

   We wish to thank every one of the people responsible, and we encourage you
   to join them in making this FAQ even better.
