Linux Kernel Configuration

Build Targets

These targets build the kernel itself in a variety of ways.

Table 11.4. Build targets

Target	Description
`all`	Builds all of the different targets needed for this kernel to be able to be used. This includes both the modules and the static portion of the kernel.
`vmlinux`	Builds just the static portion of the kernel, not any loadable modules.
`modules`	Builds all of the loadable kernel modules for this configuration.
`modules_install`	Installs all of the modules into the specified location. If no location is specified with the `INSTALL_MODULE_PATH` environment variable, they are installed in the default root directory of the machine.
`dir/`	Builds all of the files in the specified directory and in all subdirectories below it.
`dir/file.`[ `o` \| `i` \| `s` ]	Builds only the specified file.
`dir/file.ko`	Builds all of the needed files and links them together to form the specified module.
`tags`	Builds all of the needed tags that most common text editors can use while editing the source code.
`TAGS`	Builds all of the needed tags that most common text editors can use while editing the source code.
`cscope`	Builds a cscope image, useful in source tree searches, of the source tree for the architecture specified by the configuration file (not all of the kernel source files).

You can also pass a number of environment variables to make that will change the build. These can be specified for almost any target.

Table 11.5. Environment variables

Variable	Value	Description
`V`	`0`	This tells the build system to run in a quiet manner, showing only the file that is currently being built, and not the entire command that is running in order to build that file. This is the default option for the build system.
`V`	`1`	This tells the build system to operate in a verbose way, showing the full command that is being used to generate each of the specific files.
`O`	`dir`	This tells the build system to locate all output files in the `dir` directory, including the kernel configuration files. This allows the kernel to be built from a read-only filesystem and have the output placed in another location.
`C`	`1`	This checks all C files that are about to be built with the `sparse` tool, which detects common programming errors in the kernel source files. sparse can be downloaded using git from `git://git.kernel.org/pub/scm/devel/sparse/sparse.git`. Nightly snapshots can be found at `https://www.codemonkey.org.uk/projects/git-snapshots/sparse/`. More information on how to use sparse can be found in the `Documentation/sparse.txt` file in the kernel source tree.
`C`	`2`	This forces all C files to be checked with the `sparse` tool, even if they did not need to be built.