NAME

       config — build system configuration files

SYNOPSIS

       config [-CVgp] [-I path] [-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.

       -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.

       -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.

Debian                                             May 8, 2007                                         CONFIG(8)