path: root/mkinitcpio.8.txt

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mkinitcpio(8)
=============

Name
----
mkinitcpio - Create an initial ramdisk environment

Synopsis
--------
'mkinitcpio' [options]

Description
-----------
Creates an initial ramdisk environment for booting the linux kernel. The
initial ramdisk is in essence a very small environment (early userspace) which
loads various kernel modules and sets up necessary things before handing over
control to init. This makes it possible to have, for example, encrypted root
filesystems and root filesystems on a software RAID array. mkinitcpio allows
for easy extension with custom hooks, has autodetection at runtime, and many
other features.

Options
-------
*-A, \--add* 'hooks'::
	Add the additional 'hooks' to the image. These will be processed in order
	after all other hooks from the config file. Multiple hooks should be
	comma-separated. This option can be specified multiple times.

*-c, \--config* 'config'::
	Use 'config' file to generate the ramdisk. Default: /etc/mkinitcpio.conf

*-g, \--generate* 'filename'::
	Generate a CPIO image as 'filename'. Default: no; this means nothing will be
	written to the filesystem unless this option is specified.

*-H, \--hookhelp* 'hookname'::
	Output help for hookname 'hookname'.

*-h, \--help*::
	Output a short overview of available command-line switches.

*-k, \--kernel* 'kernelversion'::
	Use 'kernelversion', instead of the current running kernel. This may be a
	path to a kernel image or a specific kernel version.

*-L, \--listhooks*::
	List all available hooks.

*-M, \--automods*::
	Display modules found via autodetection. mkinitcpio will automatically try to
	determine which kernel modules are needed to start your computer. This option
	lists which modules were detected.

*-n, \--nocolor*::
	Disable color output.

*-p, \--preset* 'preset'::
	Build initramfs image(s) according to specified 'preset'. This may be a file in
	/etc/mkinitcpio.d (without the .preset extension) or a full, absolute path to a
	file.

*-S, \--skiphooks* 'hooks'::
	Skip 'hooks' when generating the image. Multiple hooks should be comma-separated.
	This option can be specified multiple times.

*-s, \--save*::
	Saves the build directory for the initial ramdisk. Default: no; This means
	the directory will not be retained if this option isn't specified. Useful for
	debugging purposes.

*-t, \--builddir* 'tmpdir'::
	Use 'tmpdir' as the temporary build directory instead of /tmp. 'tmpdir'
	must exist. The 'TMPDIR' environment variable is also honored to set this
	location, but the command line option will take precedence.

*-v, \--verbose*::
	Verbose output. Outputs more information about what's happening during
	creation of the ramdisk.

*-z, \--compress* 'compress'::
	Override the compression method with the 'compress' program.

About Presets
-------------
A preset is a pre-defined definition on how to create an initial ramdisk.
Instead of specifying the configuration file and which output file, every time
you generate a new initial ramdisk, you define a preset and use the -p switch
to generate an initial ramdisk according to your preset. Presets are located in
/etc/mkinitcpio.d

About Install Hooks
-------------------
Install hooks are bash scripts which are sourced during mkinitcpio runtime in
order to add modules, binaries, and other files to the image. A variety of
functions exist to facilitate this.

*add_module* 'modname'::

	Adds the module specified by 'modname' to the image. Dependencies are derived
	and added automatically.

*add_binary* 'binary' [ 'destination' ] [ 'mode' ]::

	Adds a binary to the image. The argument 'binary' need not be an absolute
	path and, if needed, a lookup will be performed. If the binary is a dynamically
	linked ELF binary, dependencies will be automatically added. Optionally, a
	destination within the initramfs image as well as a file mode can be specified.
	By default, the desintation and mode be taken from the source derived from
	'binary'.

*add_file* 'path' [ 'destination' ] [ 'mode' ]::

	Adds a file and any needed parent directories to the image. Optionally, a
	destination within the initramfs image as well as a file mode can be specified.
	By default, the destination and mode will be taken from the source and mode of
	the file specified by the 'path'.

*add_dir* 'path'::

	Adds a directory and its parents to the image.

*add_full_dir* 'directory'::

	Recursively adds a directory to the image by walking the given path and
	calling *add_file*, *add_dir*, and *add_symlink* accordingly. This function
	will not follow symlinks, nor will it add the targets of symlinks.

*add_all_modules* [ '-f filter' ] *pattern*::

	add modules to the image, without regard for the autodetect whitelist. *pattern*
	should be a subdirectory within the kernel tree describing a subset of modules to
	be included. Further refinement can be provided via the -f flag with an extended
	regular expression.

*add_checked_modules* [ '-f filter' ] *pattern*::

	Similar to *add_all_modules* with the constraint that only modules matching the
	whitelist generated by the autodetect hook will be added to the image. If the
	autodetect hook is not present in the image, this function is identical to
	*add_all_modules*.

*add_runscript* [ 'scriptname' ]::

	Adds a runtime hook to the image, which is a busybox ash compatible shell
	script. The name of the script is guarenteed to match the name of the hook the
	script is called. It *can* be overriden, but this is not recommended, as this
	only exists for legacy compatability.

About Runtime Hooks
-------------------
Runtime hooks added to the image via the *add_runscript* function from an
install hook are able to provide extra functionality during early userspace.
Specific functions in these files will run at different times. A hook can
define one or more of these. At each hook point, hooks are run in the order
that they are defined in the HOOKS variable, except for cleanup hooks which are
run in reverse.

*run_earlyhook*::

	Functions of this name will be run once the API mounts have been setup the
	kernel command line has been parsed. Daemons needed for early userspace should
	be started from this hook point.

*run_hook*::

	Functions of this name will be run after any early hooks, and after user
	defined modules have been installed. This is the most common hook point, and
	functionality such as scanning for LVM volumes and mapping encrypted volumes
	should be performed here.

*run_latehook*::

	Functions of this name will be run after root has been mounted. This is generally
	used for further necessary setup in the real root, such as mounting other system
	partitions.

*run_cleanuphook*::

	Functions of this name are run as late as possible. Any daemons started
	from a run_earlyhook function should be shut down here in preparation for
	switching to the real root.

Early Init Environment
----------------------
mkinitcpio gives special treatment to certain environment variables passed on
the kernel command line:

*break*['=<premount|postmount>']::
	If specified, mkinitcpio will start a shell during early init. The optional
	parameter controls when this occurs: when 'premount' or no parameter are
	specified, the shell will be launched prior to mounting root. If 'postmount'
	is specified, the shell will be launched after mounting root.

*disablehooks=*'hooklist'::
	This is a comma separated list of hooks which will be skipped during early
	init.

*earlymodules=*'modulelist'::
	This is a comma separated list of modules which will be loaded prior to any
	others. This is generally not needed, and usually points to a configuration
	or kernel problem.

*quiet*::
	Causes mkinitcpio to output fewer messages during boot. Errors will not be
	suppressed.

*ro*::
	Specifies that root should be mounted with readonly permissions. This is the
	default behavior.

*rw*::
	Specifies that root should be mounted with readwrite permissions. This is
	generally only useful if your initramfs uses the 'fsck' hook.

*root=*'rootdevice'::
	This variable describes the root partition which early init will mount
	before passing control to the real init. mkinitcpio understands a variety of
	formats, the most basic of which is the path to the block device, either
	directly, such as '/dev/sda2', or using a udev symlink such as
	'/dev/disk/by-label/CorsairF80-root'.  Support for identification by LABEL or
	UUID tags are also supported, such as, 'LABEL=CorsairF80-root'. As of
	util-linux 2.22, PARTUUID is also supported.  Identification via hex encoded
	major/minor device ID is supported for legacy reasons, but should not be used.

*rootdelay=*'seconds'::
	Sets the delay, in seconds, that mkinitcpio is willing to wait for the root
	device to show up, if it is not available immediately. This defaults to 5
	seconds. If an invalid integer is passed, this variable will have no effect.

These are only the variables that the core of mkinitcpio honor. Additional
hooks may look for other environment variables and should be documented by the
help output for the hook.

Files
-----
'/etc/mkinitcpio.conf'::
	Default configuration file for mkinitcpio.

'/etc/mkinitcpio.d'::
	Folder containing mkinitcpio presets.

'/usr/lib/initcpio/install'::
'/lib/initcpio/install'::
	Search path for build time hooks.

'/usr/lib/initcpio/hooks'::
'/lib/initcpio/hooks'::
	Search path for early userspace runtime hooks.

Examples
--------
*mkinitcpio*::
	Perform a 'dry-run'. This will generate an initial ramdisk but will not
	write anything. Use -g to create the real image.

*mkinitcpio -p linux*::
	Create an initial ramdisk based on the 'linux' preset.

*mkinitcpio -g /boot/initramfs-linux.img -k /boot/vmlinuz-linux*::
	Create an initial ramdisk for the kernel at /boot/vmlinuz-linux. The
	resulting image will be written to /boot/initramfs-linux.img.

See also
--------
A more thorough article on configuring mkinitcpio:
<http://wiki.archlinux.org/index.php/Configuring_mkinitcpio>

*initrd*(4), *lsinitcpio*(1)

Bugs
----
Upon writing this manpage, there were no noticeable bugs present. Please visit
<http://bugs.archlinux.org/> for an up to date list.

Authors
-------
mkinitcpio is created and maintained by the Arch Linux Developer community.

Copyright
---------
Copyright (c) Arch Linux 2006-2012