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CONFIG(8)               FreeBSD System Manager's Manual              CONFIG(8)

NAME
     config - build system configuration files

SYNOPSIS
     config [-CVgp] [-d destdir] SYSTEM_NAME
     config [-x kernel]

DESCRIPTION
     The config utility builds a set of system configuration files from the
     file SYSTEM_NAME which describes the system to configure.  A second file
     tells config what files are needed to generate a system and can be
     augmented by configuration specific set of files that give alternate
     files for a specific machine (see the FILES section below).

     Available options and operands:

     -V               Print the config version number.

     -C               If the INCLUDE_CONFIG_FILE is present in a configuration
                      file, kernel image will contain full configuration files
                      included literally (preserving comments).  This flag is
                      kept for backward compatibility.

     -d destdir       Use destdir as the output directory, instead of the
                      default one.  Note that config does not append
                      SYSTEM_NAME to the directory given.

     -m               Print the MACHINE and MACHINE_ARCH values for this
                      kernel and exit.

     -g               Configure a system for debugging.

     -x kernel        Print kernel configuration file embedded into a kernel
                      file.  This option makes sense only if options
                      INCLUDE_CONFIG_FILE entry was present in your
                      configuration file.

     -p               Configure a system for profiling; for example, kgmon(8)
                      and gprof(1).  If two or more -p options are supplied,
                      config configures a system for high resolution
                      profiling.

     SYSTEM_NAME      Specify the name of the system configuration file
                      containing device specifications, configuration options
                      and other system parameters for one system
                      configuration.

     The config utility should be run from the conf subdirectory of the system
     source (usually /sys/ARCH/conf), where ARCH represents one of the
     architectures supported by FreeBSD.  The config utility creates the
     directory ../compile/SYSTEM_NAME or the one given with the -d option as
     necessary and places all output files there.  The output of config
     consists of a number of files; for the i386, they are: Makefile, used by
     make(1) in building the system; header files, definitions of the number
     of various devices that will be compiled into the system.

     After running config, it is necessary to run ``make depend'' in the
     directory where the new makefile was created.  The config utility prints
     a reminder of this when it completes.

     If any other error messages are produced by config, the problems in the
     configuration file should be corrected and config should be run again.
     Attempts to compile a system that had configuration errors are likely to
     fail.

DEBUG KERNELS
     Traditional BSD kernels are compiled without symbols due to the heavy
     load on the system when compiling a ``debug'' kernel.  A debug kernel
     contains complete symbols for all the source files, and enables an
     experienced kernel programmer to analyse the cause of a problem.  The
     debuggers available prior to 4.4BSD-Lite were able to find some
     information from a normal kernel; gdb(1) provides very little support for
     normal kernels, and a debug kernel is needed for any meaningful analysis.

     For reasons of history, time and space, building a debug kernel is not
     the default with FreeBSD: a debug kernel takes up to 30% longer to build
     and requires about 30 MB of disk storage in the build directory, compared
     to about 6 MB for a non-debug kernel.  A debug kernel is about 11 MB in
     size, compared to about 2 MB for a non-debug kernel.  This space is used
     both in the root file system and at run time in memory.  Use the -g
     option to build a debug kernel.  With this option, config causes two
     kernel files to be built in the kernel build directory:

     +o   kernel.debug is the complete debug kernel.

     +o   kernel is a copy of the kernel with the debug symbols stripped off.
         This is equivalent to the normal non-debug kernel.

     There is currently little sense in installing and booting from a debug
     kernel, since the only tools available which use the symbols do not run
     on-line.  There are therefore two options for installing a debug kernel:

     +o   ``make install'' installs kernel in the root file system.

     +o   ``make install.debug'' installs kernel.debug in the root file system.

FILES
     /sys/conf/files                                         list of common
                                                             files system is
                                                             built from
     /sys/conf/Makefile.ARCH                                 generic makefile
                                                             for the ARCH
     /sys/conf/files.ARCH                                    list of ARCH
                                                             specific files
     /sys/ARCH/compile/SYSTEM_NAME                           default kernel
                                                             build directory
                                                             for system
                                                             SYSTEM_NAME on
                                                             ARCH.

SEE ALSO
     config(5)

     The SYNOPSIS portion of each device in section 4.

     Building 4.3 BSD UNIX System with Config.

HISTORY
     The config utility appeared in 4.1BSD.

     Before support for -x was introduced, options INCLUDE_CONFIG_FILE
     included entire configuration file that used to be embedded in the new
     kernel.  This meant that strings(1) could be used to extract it from a
     kernel: to extract the configuration information, you had to use the
     command:

           strings -n 3 kernel | sed -n 's/^___//p'

BUGS
     The line numbers reported in error messages are usually off by one.

FreeBSD 11.0-PRERELEASE           May 8, 2007          FreeBSD 11.0-PRERELEASE

NAME | SYNOPSIS | DESCRIPTION | DEBUG KERNELS | FILES | SEE ALSO | HISTORY | BUGS

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