KERNEL BUILD CONFIGURATION

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.

LINT CONFIGURATION

A so-called “lint” configuration should include everything from the kernel that can possibly be selected. The rationale is to provide a way to reach all the code a user might select, in order to make sure all options and drivers compile without error for a given source tree.

When used with the -L flag, config takes the regular configuration file config-file and prints on the standard output a configuration file that includes config-file, selects all options and file-systems the user can possibly select, and defines an instance of every possible attachment as described by the kernel option definition files used by config-file.

The resulting configuration file is meant as a way to select all possible features in order to test that each of them compiles. It is not meant to result in a kernel binary that can run on any hardware.

Unlike the first synopsis form, the provided srcdir is relative to the current working directory. In the first synopsis form, it is relative to the build directory.