depmod8

Usage

Overview

Linux kernel modules can provide services (called "symbols") for other modules to use (using one of the EXPORT_SYMBOL variants in the code). If a second module uses this symbol, that second module clearly depends on the first module. These dependencies can get quite complex.

depmod creates a list of module dependencies by reading each module under <BASEDIR>/<MODULEDIR>/version. By default <MODULEDIR> is /lib/modules and <BASEDIR> is empty. See options below to override when needed. It determines what symbols each module exports and needs. This list is written to modules.dep, and a binary hashed version named modules.dep.bin, in the same directory. If filenames are given on the command line, only those modules are examined (which is rarely useful unless all modules are listed). depmod also creates a list of symbols provided by modules in the file named modules.symbols and its binary hashed version, modules.symbols.bin. Finally, depmod will output a file named modules.devname if modules supply special device names (devname) that should be populated in /dev on boot (by a utility such as systemd-tmpfiles).

If a version is provided, then that kernel version's module directory is used rather than the current kernel version (as returned by uname -r).

Options

-a, --all

Probe all modules. This option is enabled by default if no file names are given in the command-line.

-A, --quick

This option scans to see if any modules are newer than the modules.dep file before any work is done: if not, it silently exits rather than regenerating the files.

-b basedir, --basedir=basedir

Override the base directory <BASEDIR> where modules are located. If your modules are not currently in the (normal) directory /lib/modules/version, but in a staging area, you can specify a basedir which is prepended to the directory name. This basedir is stripped from the resulting modules.dep file, so it is ready to be moved into the normal location. Use this option if you are a distribution vendor who needs to pre-generate the meta-data files rather than running depmod again later.

If a relative path is given, it's relative to the current working directory.

Example:

depmod -b /my/build/staging/dir/

This expects all input files under /my/build/staging/dir/lib/modules/$(uname -r) and generates index files under that same directory.

-m moduledir, --moduledir=moduledir

Override the module directory <MODULEDIR>, which defaults to /lib/modules prefix set at build time. This is useful when building modules.dep file in basedir for a system that uses a different prefix, e.g. /usr/lib/modules vs /lib/modules.

Relative and absolute paths are accepted, but they are always relative to the basedir.

Examples:

depmod -b /tmp/build -m /kernel-modules
depmod -b /tmp/build -m kernel-modules

This expects all input files under /tmp/build/kernel-modules/$(uname -r) and generates index files under that same directory.

Without an accompanying -b argument, the moduledir is relative to /. Example:

depmod -m foo/bar

This expects all input files under /foo/bar/$(uname -r) and generates index files under the same directory. Unless libkmod is prepared to handle that arbitrary location, it won't work in runtime.

-o outdir, --outdir=outdir

Set the output directory where depmod will store any generated file. outdir serves as a root to that location, similar to how basedir is used. Also this setting takes precedence and if used together with basedir it will result in the input being that directory, but the output being the one set by outdir.

If a relative path is given, it's relative to the current working directory.

Example:

depmod -o /my/build/staging/dir/

This expects all input files under /lib/modules/$(uname -r) and generates index files under /my/build/staging/dir/lib/modules/$(uname -r).

-C file or directory, --config=file or directory

-e, --errsyms

When combined with the -F option, this reports any symbols which a module needs which are not supplied by other modules or the kernel. Normally, any symbols not provided by modules are assumed to be provided by the kernel (which should be true in a perfect world), but this assumption can break especially when additionally updated third party drivers are not correctly installed or were built incorrectly.

-E Module.symvers, --symvers=Module.symvers

When combined with the -e option, this reports any symbol versions supplied by modules that do not match with the symbol versions provided by the kernel in its Module.symvers. This option is mutually incompatible with -F.

-F System.map, --filesyms=System.map

Supplied with the System.map produced when the kernel was built, this allows the -e option to report unresolved symbols. This option is mutually incompatible with -E.

-h, --help

Print the help message and exit.

-n, --show, --dry-run

This sends the resulting modules.dep and the various map files to standard output rather than writing them into the module directory.

-P

Some architectures prefix symbols with an extraneous character. This specifies a prefix character (for example '_') to ignore.

-v, --verbose

In verbose mode, depmod will print (to stdout) all the symbols each module depends on and the module's file name which provides that symbol.

-V, --version

Show version of program and exit. See below for caveats when run on older kernels.

-w

Warn on duplicate dependencies, aliases, symbol versions, etc.