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:

     •   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.

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.