CONFIG(8) BSD System Manager's Manual CONFIG(8)NAMEconfig — build system configuration files
SYNOPSISconfig [-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 aug‐
mented 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 sys‐
tem 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 archi‐
tectures 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 direc‐
tory 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 con‐
tains complete symbols for all the source files, and enables an experi‐
enced 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 ker‐
nel 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 ALSOconfig(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 com‐
mand:
strings -n 3 kernel | sed -n 's/^___//p'
BUGS
The line numbers reported in error messages are usually off by one.
BSD May 8, 2007 BSD
