DRACUT(8)

NAME
dracut - low-level tool for generating an initramfs image

SYNOPSIS

dracut [OPTION...] [<image> [<kernel version>]]

DESCRIPTION

Create an initramfs <image> for the kernel with the version <kernel version>. If <kernel version> is omitted, then the version of the actual running kernel is used. If <image> is omitted or empty, then the default location /boot/initramfs-<kernel version>.img is used.

dracut creates an initial image used by the kernel for preloading the block device modules (such as IDE, SCSI or RAID) which are needed to access the root filesystem, mounting the root filesystem and booting into the real system.

At boot time, the kernel unpacks that archive into RAM disk, mounts and uses it as initial root file system. All finding of the root device happens in this early userspace.

For a complete list of kernel command line options see dracut.cmdline(7).

EXAMPLE

To create a initramfs image, the most simple command is:

    # dracut

This will generate a general purpose initramfs image, with all possible functionality resulting of the combination of the installed dracut modules and system tools. The image is /boot/initramfs-<kernel version>.img and contains the kernel modules of the currently active kernel with version <kernel version>.

If the initramfs image already exists, dracut will display an error message, and to overwrite the existing image, you have to use the --force option.

    # dracut --force

If you want to specify another filename for the resulting image you would issue a command like:

    # dracut foobar.img

To generate an image for a specific kernel version, the command would be:

    # dracut foobar.img 2.6.40-1.rc5.f20

A shortcut to generate the image at the default location for a specific kernel version is:

    # dracut --kver 2.6.40-1.rc5.f20

If you want to create lighter, smaller initramfs images, you may want to specify the --host-only or -H option. Using this option, the resulting image will contain only those dracut modules, kernel modules and filesystems, which are needed to boot this specific machine. This has the drawback, that you can’t put the disk on another controller or machine, and that you can’t switch to another root filesystem, without recreating the initramfs image. The usage of the --host-only option is only for experts and you will have to keep the broken pieces. At least keep a copy of a general purpose image (and corresponding kernel) as a fallback to rescue your system.

OPTIONS

--kver <kernel version>
    set the kernel version. This enables to specify the kernel version, without specifying the location of the initramfs image. For example:

    # dracut --kver 3.5.0-0.rc7.git1.2.fc18.x86_64

-f, --force
    overwrite existing initramfs file.

-m, --modules <list of dracut modules>
    specify a space-separated list of dracut modules to call when building the initramfs. Modules are located in /usr/lib/dracut/modules.d. This parameter can be specified multiple times.

        Note
        If [LIST] has multiple arguments, then you have to put these in quotes. For example:

            # dracut --modules "module1 module2"  ...

-o, --omit <list of dracut modules>
    omit a space-separated list of dracut modules. This parameter can be specified multiple times.

        Note
        If [LIST] has multiple arguments, then you have to put these in quotes. For example:

            # dracut --omit "module1 module2"  ...

-a, --add <list of dracut modules>
    add a space-separated list of dracut modules to the default set of modules. This parameter can be specified multiple times.

        Note
        If [LIST] has multiple arguments, then you have to put these in quotes. For example:

            # dracut --add "module1 module2"  ...

--force-add <list of dracut modules>
    force to add a space-separated list of dracut modules to the default set of modules, when -H is specified. This parameter can be specified multiple times.

        Note
        If [LIST] has multiple arguments, then you have to put these in quotes. For example:

            # dracut --force-add "module1 module2"  ...

-d, --drivers <list of kernel modules>
    specify a space-separated list of kernel modules to exclusively include in the initramfs. The kernel modules have to be specified without the ".ko" suffix. This parameter can be specified multiple times.

        Note
        If [LIST] has multiple arguments, then you have to put these in quotes. For example:

            # dracut --drivers "kmodule1 kmodule2"  ...

--add-drivers <list of kernel modules>
    specify a space-separated list of kernel modules to add to the initramfs. The kernel modules have to be specified without the ".ko" suffix. This parameter can be specified multiple times.

        Note
        If [LIST] has multiple arguments, then you have to put these in quotes. For example:

            # dracut --add-drivers "kmodule1 kmodule2"  ...

--omit-drivers <list of kernel modules>
    specify a space-separated list of kernel modules not to add to the initramfs. The kernel modules have to be specified without the ".ko" suffix. This parameter can be specified multiple times.

        Note
        If [LIST] has multiple arguments, then you have to put these in quotes. For example:

            # dracut --omit-drivers "kmodule1 kmodule2"  ...

--filesystems <list of filesystems>
    specify a space-separated list of kernel filesystem modules to exclusively include in the generic initramfs. This parameter can be specified multiple times.

        Note
        If [LIST] has multiple arguments, then you have to put these in quotes. For example:

            # dracut --filesystems "filesystem1 filesystem2"  ...

-k, --kmoddir <kernel directory>
    specify the directory, where to look for kernel modules

--fwdir <dir>[:<dir>...]++
    specify additional directories, where to look for firmwares. This parameter can be specified multiple times.

--kernel-only
    only install kernel drivers and firmware files

--no-kernel
    do not install kernel drivers and firmware files

--mdadmconf
    include local /etc/mdadm.conf

--nomdadmconf
    do not include local /etc/mdadm.conf

--lvmconf
    include local /etc/lvm/lvm.conf

--nolvmconf
    do not include local /etc/lvm/lvm.conf

--fscks [LIST]
    add a space-separated list of fsck tools, in addition to dracut.conf's specification; the installation is opportunistic (non-existing tools are ignored)

        Note
        If [LIST] has multiple arguments, then you have to put these in quotes. For example:

            # dracut --fscks "fsck.foo barfsck"  ...

--nofscks
    inhibit installation of any fsck tools

--strip
    strip binaries in the initramfs

--nostrip
    do not strip binaries in the initramfs (default)

--hardlink
    hardlink files in the initramfs (default)

--nohardlink
    do not hardlink files in the initramfs

--prefix <dir>
    prefix initramfs files with the specified directory

--noprefix
    do not prefix initramfs files (default)

-h, --help
    display help text and exit.

--debug
    output debug information of the build process

-v, --verbose
    increase verbosity level (default is info(4))

-q, --quiet
    decrease verbosity level (default is info(4))

-c, --conf <dracut configuration file>
    specify configuration file to use.

    Default: /etc/dracut.conf

--confdir <configuration directory>
    specify configuration directory to use.

    Default: /etc/dracut.conf.d

--tmpdir <temporary directory>
    specify temporary directory to use.

    Default: /var/tmp

--sshkey <sshkey file>
    ssh key file used with ssh-client module.

-l, --local
    activates the local mode. dracut will use modules from the current working directory instead of the system-wide installed modules in /usr/lib/dracut/modules.d. This is useful when running dracut from a git checkout.

-H, --hostonly
    Host-Only mode: Install only what is needed for booting the local host instead of a generic host and generate host-specific configuration.

        Warning
        If chrooted to another root other than the real root device, use "--fstab" and provide a valid /etc/fstab.

-N, --no-hostonly
    Disable Host-Only mode

--fstab
    Use /etc/fstab instead of /proc/self/mountinfo.

--add-fstab _<filename>_
    Add entries of <filename> to the initramfs /etc/fstab.

--mount "<device> <mountpoint> <filesystem type> <filesystem options>"
    Mount <device> on <mountpoint> with <filesystem type> and <filesystem options> in the initramfs

-i, --include <SOURCE>_ _<TARGET>
    include the files in the SOURCE directory into the TARGET directory in the final initramfs. If SOURCE is a file, it will be installed to TARGET in the final initramfs. This parameter can be specified multiple times.

-I, --install <file list>
    install the space separated list of files into the initramfs.

        Note
        If [LIST] has multiple arguments, then you have to put these in quotes. For example:

            # dracut --install "/bin/foo /sbin/bar"  ...

--gzip
    Compress the generated initramfs using gzip. This will be done by default, unless another compression option or --no-compress is passed. Equivalent to "--compress=gzip -9"

--bzip2
    Compress the generated initramfs using bzip2.

        Warning
        Make sure your kernel has bzip2 decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=bzip2"

--lzma
    Compress the generated initramfs using lzma.

        Warning
        Make sure your kernel has lzma decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=lzma -9"

--xz
    Compress the generated initramfs using xz.

        Warning
        Make sure your kernel has xz decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=xz --check=crc32 --lzma2=dict=1MiB"

--compress <compressor>
    Compress the generated initramfs using the passed compression program. If you pass it just the name of a compression program, it will call that program with known-working arguments. If you pass a quoted string with arguments, it will be called with exactly those arguments. Depending on what you pass, this may result in an initramfs that the kernel cannot decompress.

--no-compress
    Do not compress the generated initramfs. This will override any other compression options.

--list-modules
    List all available dracut modules.

-M, --show-modules
    Print included module’s name to standard output during build.

--keep
    Keep the initramfs temporary directory for debugging purposes.

FILES

/var/log/dracut.log
    logfile of initramfs image creation

/tmp/dracut.log
    logfile of initramfs image creation, if /var/log/dracut.log is not writable

/etc/dracut.conf
    see dracut.conf5

/etc/dracut.conf.d/*.conf
    see dracut.conf5

  Configuration in the initramfs

/etc/conf.d/
    Any files found in /etc/conf.d/ will be sourced in the initramfs to set initial values. Command line options will override these values set in the configuration files.

/etc/cmdline
    Can contain additional command line options.

AVAILABILITY

The dracut command is part of the dracut package and is available from https://dracut.wiki.kernel.org

AUTHORS

Harald Hoyer

Victor Lowther

Philippe Seewer

Warren Togami

Amadeusz Żołnowski

Jeremy Katz

David Dillow

Will Woods

SEE ALSO

dracut.cmdline(7) dracut.conf(5)