build system configuration files
utility builds a set of system
configuration files from the file SYSTEM_NAME
which describes the system to configure. A second file tells
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
Available options and operands:
- Print the
config version number.
- 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.
- Search in path for any file included by
include directive. This option may
be specified more than once.
- Use destdir as the output directory,
instead of the default one. Note that
config does not append
SYSTEM_NAME to the directory given.
- Use srcdir as the source directory,
instead of the default one.
- Print the MACHINE and MACHINE_ARCH values for this kernel and exit.
- Configure a system for debugging.
- Print kernel configuration file embedded into a kernel file. This option
makes sense only if
INCLUDE_CONFIG_FILE entry was present in your configuration
- Configure a system for profiling; for example,
If two or more
-p options are supplied,
config configures a system for high
- Specify the name of the system configuration file containing device
specifications, configuration options and other system parameters for one
utility should be run from the
subdirectory of the system source
represents one of the
architectures supported by FreeBSD
utility creates the directory
or the one given with the
necessary and places all output files there. The output of
consists of a number of files; for
the i386, they are: Makefile
, used by
in building the system; header files, definitions of the number of various
devices that will be compiled into the system.
utility looks for kernel sources
in the directory ../..
or the one given
, it is necessary to run
” in the directory where the
new makefile was created. The
utility prints a reminder of this when it completes.
If any other error messages are produced by
, the problems in the configuration
file should be corrected and
be run again. Attempts to compile a system that had configuration errors are
likely to fail.
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;
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
option to build a debug kernel. With
causes two kernel files
to be built in the kernel build directory:
- kernel.debug is the complete debug
- kernel is a copy of the kernel with the
debug symbols stripped off. This is equivalent to the normal non-debug
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
- list of common files system is built from
- generic makefile for the ARCH
- list of ARCH specific files
- default kernel build directory for system
portion of each
device in section 4.
Building 4.3 BSD UNIX System with
utility appeared in
Before support for
configuration file that used to be embedded in the new kernel. This meant that
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
The line numbers reported in error messages are usually off by one.