There are several different ways to run the
config program. The traditional way is to run
config from the
conf subdirectory of the machine-specific directory of the system source (usually
/sys/arch/MACHINE/conf, where
MACHINE is one of
vax,
hp300, and so forth), and to specify as the
config-file the name of a machine description file located in that directory.
config will by default create files in the directory
../compile/SYSTEMNAME, where
SYSTEMNAME is the last path component of
config-file.
config will assume that the top-level kernel source directory is located four directories above the build directory.
Another way is to create the build directory yourself, place the machine description file in the build directory with the name
CONFIG, and run
config from within the build directory without specifying a
config-file.
config will then by default create files in the current directory. If you run
config this way, you must specify the location of the top-level kernel source directory using the
-s option or by using the “
source” directive at the beginning of the machine description file.
Finally, you can specify the build directory for
config and run it from anywhere. You can specify a build directory with the
-b option or by using the “
build” directive at the beginning of the machine description file. You must specify the location of the top-level kernel source directory if you specify a build directory.
If
config-file is a binary kernel,
config will try to extract the configuration file embedded into it, which will be present if that kernel was built either with
INCLUDE_CONFIG_FILE or
INCLUDE_JUST_CONFIG options. This work mode requires you to manually specify a build directory with the
-b option, which implies the need to provide a source tree too.
If the
-p option is supplied,
.PROF is appended to the default compilation directory name, and
config acts as if the lines “
makeoptions PROF="-pg"” and “
options GPROF” appeared in the machine description file. This will build a system that includes profiling code; see
kgmon(8) and
gprof(1). The
-p flag is expected to be used for “one-shot” profiles of existing systems; for regular profiling, it is probably wiser to create a separate machine description file containing the
makeoptions line.
The old undocumented
-g flag is no longer supported. Instead, use “
makeoptions DEBUG="-g"” and (typically) “
options KGDB”.
The output of
config consists of a number of files, principally
ioconf.c, a description of I/O devices that may be attached to the system; and a
Makefile, used by
make(1) in building the kernel.
After running
config, it is wise to run “
make depend” in the directory where the new makefile was created.
config prints a reminder of this when it completes.
If
config stops due to errors, the problems reported should be corrected and
config should be run again.
config attempts to avoid changing the compilation directory if there are configuration errors, but this code is not well-tested, and some problems (such as running out of disk space) are unrecoverable.