mkinitcpio

MKINITCPIO(8)                  mkinitcpio manual                 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, --addhooks 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

       -d, --generatedir directory
           Set directory as the location where the initramfs is built. This
           might be useful to generate a shutdown ramfs in /run/initramfs.

       -D, --hookdir directory
           Set directory as the location where hooks will be searched for when
           generating the image.

       -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 (only supported for x86-based
           architectures), a specific kernel version or the special keyword
           none. In the latter case, no kernel modules are added to the image.

       -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, --allpresets
           Process all presets contained in /etc/mkinitcpio.d. See the -p
           option for more detail about presets.

       -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. This option may be specified
           multiple times to process multiple presets.

       -r, --moduleroot root
           Specifies the root directory to find modules in, defaulting to /.

       -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, --version
           Display version information.

       -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
           destintation 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 [ glob ] [ strip_prefix ]
           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.

               If the 'glob' argument is passed, only files and symlinks matching this glob
               will be added.

               If the 'strip_prefix' argument is passed, it will be used to strip the
               destination path (path in the initramfs image) from the prefix specified by
               the 'strip_prefix' argument. This can be useful when writing rootfs-overlay
               hooks.

       add_symlink path [ link-target ]
           Adds a symlink to the image at the specified path, optionally
           pointing to the specified link-target. If the link-target is not
           provided, it is assumed that this symlink exists in the real
           filesystem, and the target will be read using readlink. There is no
           checking done to ensure that the target of the symlink exists, and
           symlinks will not be followed recursively.

       add_all_modules [ -f filter ] pattern
           Adds 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
           Adds a runtime hook to the image, which is a busybox ash compatible
           shell script. The name of the script is guaranteed to match the
           name of the hook the script is called from.

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 and 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 and PARTLABEL are also supported. Identification via hex
           encoded major/minor device ID is supported for legacy reasons, but
           should be avoided as it tends to be fragile.

       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 10 seconds. If an invalid integer is passed, this
           variable will have no effect.

       rootflags=flaglist
           A comma-separated list of flags which will be passed onto the
           mount(8) command when mounting the root filesystem. Acceptable
           values are filesystem specific.

       rootfstype=fstype
           Overrides the type of filesystem being mounted as root. This should
           almost never be needed as mount(8) usually detects this on its own.

       rd.debug
           Enables shell debug (xtrace). If rd.log is not also a parameter on
           the kernel command line, this parameter implies rd.log=console.

       rd.log[=<console|file|kmsg|all>]
           Enables logging of early userspace messages. If specified, the
           optional parameter describes where this information is logged.
           Multiple options can be OR’d together using the pipe (|) character.
           Messages are always logged to the console unless the quiet
           parameter is passed. If the optional parameter is not specified,
           kmsg|console is assumed. If rd.log is not present on the kernel
           command line, no logging will take place.

           console
               Writes output to /dev/console.

           file
               Writes output to /run/initramfs/init.log.

           kmsg
               Writes output to the /dev/kmsg device (introduced in Linux
               3.5). This option is a no-op if your kernel lacks support for
               /dev/kmsg.

           all
               Writes output to all known log targets.

       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.

REPRODUCIBILITY
       mkinitcpio aims to create reproducible initramfs images by default.

       This means that two subsequent runs of mkinitcpio should produce two
       files that are identical at the binary level.

       Timestamps within the initramfs are set to the Unix epoch of
       1970-01-01.

       Note that in order for the build to be fully reproducible, the
       compressor specified (e.g. gzip, xz) must also produce reproducible
       archives. At the time of writing, as an inexhaustive example, the lzop
       compressor is incapable of producing reproducible archives due to the
       insertion of a runtime timestamp.

       More information can be found at https://reproducible-builds.org.

FILES
       /etc/mkinitcpio.conf
           Default configuration file for mkinitcpio.

       /etc/mkinitcpio.d
           Directory containing mkinitcpio presets.

       /etc/initcpio/install, /usr/lib/initcpio/install
           Search path for build time hooks.

       /etc/initcpio/hooks, /usr/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/Mkinitcpio

       initrd(4), lsinitcpio(1), mkinitcpio.conf(5), bootparam(7)

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 2006-2019



  mkinitcpio 26                   10/07/2019                     MKINITCPIO(8)