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

     config — build system configuration files

     config [-CVgp] [-I path] [-d destdir] [-s srcdir] SYSTEM_NAME
     config [-x kernel]

     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.

     -I path      Search in path for any file included by the include directive.
                  This option may be specified more than once.

     -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.

     -s srcdir    Use srcdir as the source directory, instead of the default

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

     -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.

     The config utility looks for kernel sources in the directory ../.. or the
     one given with the -s option.

     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

     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:

     kernel.debug is the complete debug kernel.

     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:

     “make install” installs kernel in the root file system.

     “make install.debug” installs kernel.debug in the root file system.

     /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.


     The SYNOPSIS portion of each device in section 4.

     Building 4.3 BSD UNIX System with Config.

     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'

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

BSD                               June 29, 2020                              BSD