modules.conf - configuration file for loading kernel modules

The behavior of modprobe(8) (and depmod(8) ) can be modified by the (optional) configuration file /etc/modules.conf.

The configuration file consists of a set of lines.

All empty lines, and all text on a line after a '#', will be ignored.

Lines may be continued by ending the line with a '\'.

The remaining lines should all conform to one of the following formats:

[add] above module module_list alias alias_name result [add] below module module_list define VARIABLE WORD depfile=A_PATH else elseif EXPRESSION endif if EXPRESSION include PATH_TO_CONFIG_FILE insmod_opt=GENERIC_OPTIONS_TO_INSMOD install module command ... keep [add] options module MODULE_SPECIFIC_OPTIONS path=A_PATH path[TAG]=A_PATH generic_stringfile=A_PATH pcimapfile=A_PATH isapnpmapfile=A_PATH usbmapfile=A_PATH parportmapfile=A_PATH ieee1394mapfile=A_PATH pnpbiosmapfile=A_PATH [add] probe name module_list [add] probeall name module_list prune filename post-install module command ... post-remove module command ... pre-install module command ... pre-remove module command ... remove module command ... persistdir directory_name

All arguments to a directive will be processed to handle shell meta-characters, which means that "shell tricks" like wild-cards and commands enclosed in back-quotes can be used:

path[misc]=/lib/modules/1.1.5?/local path[net]=/lib/modules/`uname -r`/net

DANGER: Applying shell expansion to user supplied input is a major security risk. Modutils code only does meta expansion via shell commands for trusted data. Basically this means only for data in the config file. Even that assumes that the user cannot run modprobe as root while supplying their own config file. Programs (including the kernel) that invoke modutils programs as root with user supplied input must pass exactly one user supplied parameter and must set safe mode or risk creating local root exploits. See modprobe for details on safe mode.

Directives may be repeated multiple times. Note that some directives can have an optional prefix: add. When this prefix is used, the new module_list will be added to the previous module_list instead of replacing it.

All commands (in post-install, post-remove, pre-install, pre-remove, and remove) are executed using the system() call. Commands need to be posixly correct, as they will be processed by /bin/sh.

Notice that in systems running Debian GNU/Linux, this file is automatically generated by the script update-modules based on the contents in /etc/modutils/. If you want to manage this file by yourself make sure you remove the first header line which indicates to the script that it can regenerate it. If you don't, your local changes will be lost on package upgrade. Instead of modifying this file you should modify the content of files under the /etc/modutils/ directory.

A_PATH is the fully qualified path to the target. It is possible to use shell meta-characters in A_PATH including command output, such as `uname -r` and `kernelversion`.

These two commands are also understood internally in these utilities as meaning the version number of the current kernel and the current kernel version respectively (e.g.: 2.2.3 and 2.2).

WORD is a sequence if non-white characters. If ' " or ` is found in the string, all characters up to the matching ' " or ` will also be included, even whitespace. Every WORD will then be expanded w.r.t. meta-characters. If the expanded result gives more than one word then only the first word of the result will be used.

EXPRESSION below can be:

WORD compare_op WORD

where compare_op is one of ==, !=, <, <=, >= or >. The string values of the WORDs are compared.

-n WORD compare_op WORD

where compare_op is one of ==, !=, <, <=, >= or >. The numeric values of the WORDs are compared.

WORD

If the expansion of WORD fails, or if the expansion is "0" (zero), "false" or "" (empty) then the expansion has the value FALSE. Otherwise the expansion has the value TRUE

-f FILENAME

Test if the file FILENAME exists.

-k

Test if "autoclean" is enabled (i.e. called from the kernel).

! EXPRESSION

A negated expression is also an expression.

This is a description of the legal directives.

define VARIABLE WORD

Do a putenv(" VARIABLE=WORD" ). Variables can be created and modified by this directive. The variables will be available in the environment, which makes them usable for all commands executed in the current session.

depfile=A_PATH

This is the path to the dependency file that will be created by depmod and used by modprobe to find the modules and their dependent modules. Normally the default value should be used, see below.

if EXPRESSION

If the expression is evaluated to be TRUE then all directives up to the matching else, elseif or endif are processed. Otherwise they are ignored. if directives may be nested up to an internal maximum of 20.

Note: please avoid having any path directives conditionally processed. Since modprobe has enough built-in "smarts", a conditionally processed path directive will gain you nothing but confusion. Really.

else

If the previous matching if or elseif directive evaluated its expression to be FALSE then the directives enclosed by the (optional) else directive and its matching endif directive will be processed.

elseif EXPRESSION

If the previous matching if or elseif directives evaluated their expression to be FALSE and if the expression for this directive evaluates to TRUE then the directives up to the next matching elseif, else or endif directive will be processed.

endif

This directive ends the chain of matching if, elseif or else directive(s) controlling the conditional processing of configuration file directives.

if EXPRESSION any config lines elseif EXPRESSION any config lines else any config lines endif

The else and elseif directives are optional.

include PATH_TO_CONFIG_FILE

To handle different platforms or configurations with a single configuration file can be quite complex. With the use of the include directive, conditionally processed by if directives, this is now easier to handle.

insmod_opt=GENERIC_OPTIONS_TO_INSMOD

If insmod should need some special options, not specified elsewhere, this directive makes it possible to add such an option, to be used for every invocation. The standard default options to insmod does normally not have to be modified unless some special situation needs to be handled.

keep

If this word is found on a line before any lines that contain the path descriptions, the default set of paths will be saved, and thus added to. Otherwise the normal behavior is that the default set will be replaced by the set of paths in the configuration file.

path=A_PATH

path[TAG]=A_PATH

The A_PATH argument specifies an additional directory to search for modules. The path directive can carry an optional tag. This tells us a little more about the purpose of the modules in this directory and allows some automated operations by modprobe. The tag is appended to the "path" keyword enclosed in square brackets. If the tag is missing, the tag "misc" is assumed.

One very useful tag is boot, which can be used to mark all directories containing modules that should be loaded at boot-time.

Note that you must specify the keep directive to prevent any path directives from over-riding the default paths.

generic_stringfile=A_PATH

This is the path to the generic_string file that will be created by depmod and used by install scripts that need string information from modules. Normally the default value should be used, see below. pcimapfile=A_PATH This is the path to the pcimap file that will be created by depmod and used by install scripts to find the module that supports a pci device. Normally the default value should be used, see below.

isapnpmapfile=A_PATH

This is the path to the isapnpmap file that will be created by depmod and used by install scripts to find the module that supports an ISA PNP device. Normally the default value should be used, see below.

usbmapfile=A_PATH

This is the path to the usbmap file that will be created by depmod and used by install scripts to find the module that supports an USB device. Normally the default value should be used, see below.

parportmapfile=A_PATH

This is the path to the parportmap file that will be created by depmod and used by install scripts to find the module that supports an parport device. Normally the default value should be used, see below.

ieee1394mapfile=A_PATH

This is the path to the ieee1394map file that will be created by depmod and used by install scripts to find the module that supports an ieee1394 device. Normally the default value should be used, see below.

pnpbiosmapfile=A_PATH

This is the path to the pnpbiosmap file that will be created by depmod and used by install scripts to find the module that supports an pnpbios device. Normally the default value should be used, see below.

alias alias_name result

The "alias" directive can be used to give alias names to modules. A line in /etc/modules.conf that looks like this:

alias iso9660 isofs

makes it possible to write modprobe iso9660 although there is no object file for such a module available.

Note that the line:

alias some_module off

will make modprobe ignore requests to load that module. Another special alias is:

alias some_module null

which will make requests for some_module always succeed, but no module will actually be installed. This can be used as a base for stacks created via the above and below directives.

alias a b alias b a

If the final result of an alias mapping does not match the name of any module then modprobe applies probe and probeall mappings to the result. If those do not succeed then the module is not found. This makes constructs like this give sensible results (from devfs).

alias /dev/sg* /dev/sg probeall /dev/sg scsi-hosts sg

It is legal for an alias to map module A to module B and for module A to exist at the same time but this construct is ambiguous and is not recommended. For historical reasons, the kernel sound system has a module called sound.o but the sound developers also want an alias from sound to the module for the user's sound card, e.g. "alias sound sb". In an attempt to support this requirement but still maintain the defined behavior where options can be applied to aliases, modprobe bypasses alias expansion when processing a module name if the name was obtained via modules.dep, otherwise aliases are expanded. This is not guaranteed to give the expected behavior on all combinations of aliases and real modules, you should avoid using an alias with the same name as a real module.

[add] probe name module_list

[add] probeall name module_list

These directives can only be used when name is the name of the module requested on the command line of modprobe. The effect is that when a request for name is made, the modules in module_list will be tried, in the specified order. The difference between the directives is that probe will continue until the first successful module insertion, while probeall will continue until the end of the list. The exit status reflects whether any module has been successfully installed or not. The optional add prefix adds the new list to the previous list instead of replacing it.

prune filename

The top level module directory for a kernel install contains files which are not modules. These include modules.dep, modules.generic_string, modules.pcimap, modules.isapnpmap, modules.usbmap, modules.parportmap, modules.ieee1394map, modules.pnpbiosmap, the build symlink to the kernel source tree and any other files that the install process wants to save from a kernel build. To prevent depmod issuing warnings about "not an ELF file", these non-module files should appear in the prune list. depmod has a built in prune list which cannot be removed because it lists files which will exist for any kernel build. If you add your own files to the top level modules directory, add a prune statement for each filename. Note: The prune list is only used when scanning the top directory of a path, and only if the directory contains at least one subdirectory from the standard list of subdirectory names, i.e. it appears to be a top level directory built from a kernel install. The prune list has no effect on subdirectories of a path.

[add] options [-k] module [MODULE_SPECIFIC_OPTIONS]

All module names, including aliased names, can have their own options directives. Options specified for an alias have higher priority than the options specified for more "basic" names. This rule is used to resolve conflicting options directives. Options given on the command line have the highest priority. If there is -k before the module name, then the module won't be autocleaned even if modprobe has been invoked with the -k autoclean option. The optional add prefix adds the new list to the previous list instead of replacing it. If the result of an alias is not a real module then any options that were constructed from the alias chain are discarded before invoking probe[all]. If any of the MODULE_SPECIFIC_OPTIONS contain characters that are special to the shell (e.g. space, comma, parentheses) then the option must be enclosed in '"..."'. The '' delimit the option in modules.conf, the "" delimit the option when it is passed to the shell. For example,

abc='"def,ghi jkl (xyz)"'

[add] above module module_list

This directive makes it possible for one module to "pull in" another set of modules on top of itself in a module stack, as seen in the output of the lsmod(8) command. The above directive is useful for those circumstances when the dependencies are more complex than what can be described in the modules.dep dependency file. This is an optimized case of the post-install and pre-remove directives. Note that failure of installing the module will not influence the exit status of modprobe. The optional add prefix adds the new list to the previous list instead of replacing it.

[add] below module module_list

This directive makes it possible for one module to "push" another set of modules below itself in a module stack, as seen in the output of the lsmod(8) command. The below directive is useful for those circumstances when the dependencies are more complex than what can be described in the modules.dep dependency file. This is an optimized case of the pre-install and post-remove directives. Note that failure of installing the module will not influence the exit status of modprobe. The optional add prefix adds the new list to the previous list instead of replacing it.

The following directives are useful for (optionally) executing specific commands when loading and unloading a module. Note that even aliased module names can have these directives, which will be executed in the proper order together with any directives for the unaliased module name.

pre-install module command

Execute command before installing the specified module. See the below directive as well.

install module command

Execute command instead of the default insmod when installing the specified module.

post-install module command

Execute command after installing the specified module. See the above directive as well.

pre-remove module command

Execute command before removing the specified module. See the above directive as well.

remove module command

Execute command instead of the default (built-in) rmmod when removing the specified module.

post-remove module command

Execute command after removing the specified module. See the below directive as well.

persistdir=directory_name When rmmod removes a module that contains persistent module parameters, it stores the (possibly) modified parameters underneath directory_name. When modprobe loads a module that contains persistent module parameters, it looks under directory_name for any previous values for those parameters. You must set persistdir to the name of a directory that is readable when modules are loaded and is writable when modules are unloaded, the default value is /var/lib/modules/persist. Many Linux distributions load their modules before mounting filesystems, this can cause problems for persistent data. If /var is a separate partition and it is mounted after modules are loaded then insmod has nowhere to read persistent data from. You have two choices when /var is on a separate partition.

1) Specify persistdir pointing at a directory in the root partition, say /lib/modules/persist. This assumes that the root partition is writable when rmmod runs.

2) Load any filesystem related modules first, mount the /var partition then load the rest of the modules. This assumes that the filesystem modules have no persistent data.

If the configuration file '/etc/modules.conf' is missing, or if any directive is not overridden, the following defaults are assumed:

depfile=/lib/modules/`uname -r`/modules.dep generic_stringfile=/lib/modules/`uname -r`/modules.generic_string pcimapfile=/lib/modules/`uname -r`/modules.pcimap isapnpmapfile=/lib/modules/`uname -r`/modules.isapnpmap usbmapfile=/lib/modules/`uname -r`/modules.usbmap parportmapfile=/lib/modules/`uname -r`/modules.parportmap ieee1394mapfile=/lib/modules/`uname -r`/modules.ieee1394map pnpbiosmapfile=/lib/modules/`uname -r`/modules.pnpbiosmap

path[boot]=/lib/modules/boot path[toplevel]=/lib/modules/`uname -r` path[toplevel]=/lib/modules/`kernelversion` path[toplevel]=/lib/modules/default path[toplevel]=/lib/modules

persistdir=/var/lib/modules/persist

There are also a set of default alias and options directives. Since this set is continuously extended, no list will be given here. The (current) default set can be viewed by using the modprobe -c command with an empty /etc/modules.conf file.

All options directives specify the options needed for a module, as in:

modprobe de620 bnc=1

These options will be overridden by any options given in the /etc/modules.conf file, and on the modprobe command line.

Remember that it is possible to have an options directive for aliased module names as well as for the non-aliased name. This is useful for e.g. the dummy module:

alias dummy0 dummy options dummy0 -o dummy0

For historical reasons, if /etc/modules.conf does not exist, modutils will read /etc/conf.modules instead. However the use of this historical name is deprecated and it should be replaced with /etc/modules.conf. This version of modutils issues a warning message if /etc/conf.modules exists, later versions will give an error message and refuse to load modules.

depmod(8), modprobe(8), insmod(8), update-modules(8)

Bjorn Ekwall <bj0rn@blox.se>
Keith Owens <kaos@ocs.com.au>