dracut - Man Page

• Generate an initramfs image for the current kernel without overriding any options: dracut
• Generate an initramfs image for the current kernel and overwrite the existing one: dracut --force
• Generate an initramfs image for a specific kernel: dracut --kver kernel_version
• List available modules: dracut --list-modules

tldr.sh

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

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, the default location will be determined by the local configuration or Linux distribution policy.

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.

Initramfs images are also called "initrd".

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

If you are dropped to an emergency shell, while booting your initramfs, the file /run/initramfs/rdsosreport.txt is created, which can be saved to a (to be mounted by hand) partition (usually /boot) or a USB stick. Additional debugging info can be produced by adding rd.debug to the kernel command line. /run/initramfs/rdsosreport.txt contains all logs and the output of some tools. It should be attached to any report about dracut problems.

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 contains the kernel modules of the currently active kernel with version <kernel-version>. The default location of the image is determined by the local configuration or Linux distribution policy.

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 --hostonly 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. It is recommended to keep a copy of a general purpose image (and corresponding kernel) as a fallback to rescue your system.

# lsinitrd | less

# lsinitrd -f /etc/ld.so.conf
include ld.so.conf.d/*.conf

# dracut --add module initramfs-module.img

# dracut --list-modules

# dracut -o "multipath lvm" no-multipath-lvm.img

# dracut --add-drivers mymod initramfs-with-mymod.img

# dracut --print-cmdline
 root=UUID=8b8b6f91-95c7-4da2-831b-171e12179081 rootflags=rw,relatime,discard,data=ordered rootfstype=ext4

# dracut --include cmdline-preset /etc/cmdline.d/mycmdline.conf initramfs-cmdline-pre.img

# mkdir -p rd.live.overlay/etc/cmdline.d
# mkdir -p rd.live.overlay/etc/conf.d
# echo "ip=dhcp" >> rd.live.overlay/etc/cmdline.d/mycmdline.conf
# echo export FOO=testtest >> rd.live.overlay/etc/conf.d/testvar.conf
# echo export BAR=testtest >> rd.live.overlay/etc/conf.d/testvar.conf
# tree rd.live.overlay/
rd.live.overlay/
`-- etc
    |-- cmdline.d
    |   `-- mycmdline.conf
    `-- conf.d
        `-- testvar.conf

# dracut --include rd.live.overlay / initramfs-rd.live.overlay.img

# dracut --install 'strace fsck.ext4 ssh' initramfs-dbg.img

# dracut -m "nfs network base" initramfs-nfs-only.img

# dracut -m "nfs network base" --host-only initramfs-nfs-host-only.img

If the boot process does not succeed, you have several options to debug the situation.

# mkdir -p /run/initramfs/etc/cmdline.d
# echo "rd.debug rd.break=pre-shutdown rd.break=shutdown" > /run/initramfs/etc/cmdline.d/debug.conf
# touch /run/initramfs/.need_shutdown

--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.

<output file> --rebuild

Append the current arguments to those with which the input initramfs image was built. This option helps in incrementally building the initramfs for testing. If optional <output file> is not provided, the input initramfs provided to rebuild will be used as output file.

-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 the 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 the list has multiple arguments, then you have to put these in quotes. For example:

# dracut --force-add "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 the list has multiple arguments, then you have to put these in quotes. For example:

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

-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. This option forces dracut to only include the specified dracut modules. In most cases the "--add" option is what you want to use.

Note
If the list has multiple arguments, then you have to put these in quotes. For example:

# dracut --modules "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 the 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 the list has multiple arguments, then you have to put these in quotes. For example:

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

--force-drivers <list of kernel modules>

See add-drivers above. But in this case it is ensured that the drivers are tried to be loaded early via modprobe.

Note
If the list has multiple arguments, then you have to put these in quotes. For example:

# dracut --force-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 the 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 the 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.

--libdirs <list of directories>

Specify a space-separated list of directories to look for libraries to include in the generic initramfs. This parameter can be specified multiple times.

Note
If the list has multiple arguments, then you have to put these in quotes. For example:

# dracut --libdirs "dir1 dir2"  ...

--kernel-cmdline <parameters>

Specify default kernel command line parameters. Despite its name, this command only sets initrd parameters.

--kernel-only

Only install kernel drivers and firmware files.

--no-kernel

Do not install kernel drivers and firmware files.

--early-microcode

Combine early microcode with ramdisk.

--no-early-microcode

Do not combine early microcode with ramdisk.

--print-cmdline

Print the kernel command line for the current disk layout.

--mdadmconf

Include local /etc/mdadm.conf file.

--nomdadmconf

Do not include local /etc/mdadm.conf file.

--lvmconf

Include local /etc/lvm/lvm.conf file.

--nolvmconf

Do not include local /etc/lvm/lvm.conf file.

--fscks <list of fsck tools>

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 the 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 (default).

--aggressive-strip

Strip more than just debug symbol and sections, for a smaller initramfs build. The --strip option must also be specified.

--nostrip

Do not strip binaries in the initramfs.

--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)).

--version

Display version and exit.

-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

-r, --sysroot <sysroot directory>

Specify the sysroot directory to collect files from. This is useful to create the initramfs image from a cross-compiled sysroot directory. For the extra helper variables, see Environment below.

Default: empty

--sshkey <sshkey file>

SSH key file used with ssh-client module.

--logfile <logfile>

Logfile to use; overrides any setting from the configuration files.

Default: /var/log/dracut.log

-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.

--hostonly-mode <mode>

Specify the host-only mode to use. <mode> could be one of "sloppy" or "strict". In "sloppy" host-only mode, extra drivers and modules will be installed, so minor hardware change won’t make the image unbootable (e.g. changed keyboard), and the image is still portable among similar hosts. With "strict" mode enabled, anything not necessary for booting the local host in its current state will not be included, and modules may do some extra job to save more space. Minor change of hardware or environment could make the image unbootable.

Default: sloppy

--hostonly-cmdline

Store kernel command line arguments needed in the initramfs.

--no-hostonly-cmdline

Do not store kernel command line arguments needed in the initramfs.

--no-hostonly-default-device

Do not generate implicit host devices like root, swap, fstab, etc. Use "--mount" or "--add-device" to explicitly add devices as needed.

--hostonly-i18n

Install only needed keyboard and font files according to the host configuration (default).

--no-hostonly-i18n

Install all keyboard and font files available.

--hostonly-nics <list of nics>

Only enable listed NICs in the initramfs. The list can be empty, so other modules can install only the necessary network drivers.

--persistent-policy <policy>

Use <policy> to address disks and partitions. <policy> can be any directory name found in /dev/disk (e.g. "by-uuid", "by-label"), or "mapper" to use /dev/mapper device names (default).

--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> [<dump frequency> [<fsck order>]]]"

Mount <device> on <mountpoint> with <filesystem type> in the initramfs. <filesystem options>, <dump options> and <fsck order> can be specified, see fstab manpage for the details. The default <filesystem options> is "defaults". The default <dump frequency> is "0". The default <fsck order> is "2".

--mount "<mountpoint>"

Like above, but <device>, <filesystem type> and <filesystem options> are determined by looking at the current mounts.

--add-device <device>

Bring up <device> in initramfs, <device> should be the device name. This can be useful in host-only mode for resume support when your swap is on LVM or an encrypted partition. [NB --device can be used for compatibility with earlier releases]

-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 the list has multiple arguments, then you have to put these in quotes. For example:

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

--install-optional <file list>

Install the space separated list of files into the initramfs, if they exist.

--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 -9".

--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 -T0".

--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 -T0".

--lzo

Compress the generated initramfs using lzop.

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

--lz4

Compress the generated initramfs using lz4.

Warning
Make sure your kernel has lz4 decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=lz4 -l -9".

--zstd

Compress the generated initramfs using Zstandard.

Warning
Make sure your kernel has zstd decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=zstd -15 -q -T0".

--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. The default value can also be set via the INITRD_COMPRESS environment variable.

--squash-compressor <compressor>

Compress the squashfs image using the passed compressor and compressor specific options for mksquashfs. You can refer to mksquashfs manual for supported compressors and compressor specific options. If squash module is not called when building the initramfs, this option will not take effect.

--no-compress

Do not compress the generated initramfs. This will override any other compression options.

--reproducible

Create reproducible images.

--no-reproducible

Do not create reproducible images.

--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.

--printsize

Print out the module install size.

--profile

Output profile information of the build process.

--ro-mnt

Mount / and /usr read-only by default.

-L, --stdlog <level>

[0-6] Specify logging level (to standard error).

          0 - suppress any messages
          1 - only fatal errors
          2 - all errors
          3 - warnings
          4 - info
          5 - debug info (here starts lots of output)
          6 - trace info (and even more)

--regenerate-all

Regenerate all initramfs images at the default location with the kernel versions found on the system. Additional parameters are passed through.

-p,  --parallel

Try to execute tasks in parallel. Currently only supported with --regenerate-all (build initramfs images for all kernel versions simultaneously).

--noimageifnotneeded

Do not create an image in host-only mode, if no kernel driver is needed and no /etc/cmdline/*.conf will be generated into the initramfs.

--loginstall <directory>

Log all files installed from the host to <directory>.

--uefi

Instead of creating an initramfs image, dracut will create an UEFI executable, which can be executed by an UEFI BIOS. The default output filename is <EFI>/EFI/Linux/linux-$kernel$-<MACHINE_ID>-<BUILD_ID>.efi. <EFI> might be /efi, /boot or /boot/efi depending on where the ESP partition is mounted. The <BUILD_ID> is taken from BUILD_ID in /usr/lib/os-release or if it exists /etc/os-release and is left out, if BUILD_ID is non-existent or empty.

--no-uefi

Disables UEFI mode.

--no-machineid

Affects the default output filename of --uefi and will discard the <MACHINE_ID> part.

--uefi-stub <file>

Specifies the UEFI stub loader, which will load the attached kernel, initramfs and kernel command line and boots the kernel. The default is $prefix/lib/systemd/boot/efi/linux<EFI-MACHINE-TYPE-NAME>.efi.stub.

--uefi-splash-image <file>

Specifies the UEFI stub loader’s splash image. Requires bitmap (.bmp) image format.

--kernel-image <file>

Specifies the kernel image, which to include in the UEFI executable. The default is /lib/modules/<KERNEL-VERSION>/vmlinuz or /boot/vmlinuz-<KERNEL-VERSION>.

--sbat <parameters>

Specifies the SBAT parameters, which to include in the UEFI executable. By default the default SBAT string added is "sbat,1,SBAT Version,sbat,1, https://github.com/rhboot/shim/blob/main/SBAT.md".

--enhanced-cpio

Attempt to use the dracut-cpio binary, which optimizes archive creation for copy-on-write filesystems by using the copy_file_range(2) syscall via Rust’s io::copy(). When specified, initramfs archives are also padded to ensure optimal data alignment for extent sharing. To retain reflink data deduplication benefits, this should be used alongside the --no-compress and --nostrip parameters, with initramfs source files, --tmpdir staging area and destination all on the same copy-on-write capable filesystem.

INITRD_COMPRESS

sets the default compression program. See --compress.

DRACUT_LDCONFIG

sets the ldconfig program path and options. Optional. Used for --sysroot.

Default: ldconfig

DRACUT_LDD

sets the ldd program path and options. Optional. Used for --sysroot.

Default: ldd

DRACUT_TESTBIN

sets the initially tested binary for detecting library paths. Optional. Used for --sysroot. In the cross-compiled sysroot, the default value (/bin/sh) is unusable, as it is an absolute symlink and points outside the sysroot directory.

Default: /bin/sh

DRACUT_INSTALL

overrides path and options for executing dracut-install internally. Optional. Can be used to debug dracut-install while running the main dracut script.

Default: dracut-install

Example: DRACUT_INSTALL="valgrind dracut-install"

DRACUT_COMPRESS_BZIP2,  DRACUT_COMPRESS_LBZIP2,  DRACUT_COMPRESS_LZMA,  DRACUT_COMPRESS_XZ,  DRACUT_COMPRESS_GZIP,  DRACUT_COMPRESS_PIGZ,  DRACUT_COMPRESS_LZOP,  DRACUT_COMPRESS_ZSTD,  DRACUT_COMPRESS_LZ4,  DRACUT_COMPRESS_CAT

overrides for compression utilities to support using them from non-standard paths.

Default values are the default compression utility names to be found in PATH.

DRACUT_ARCH

overrides the value of uname -m. Used for --sysroot.

Default: empty (the value of uname -m on the host system)

SYSTEMD_VERSION

overrides systemd version. Used for --sysroot.

SYSTEMCTL

overrides the systemctl binary. Used for --sysroot.

NM_VERSION

overrides the NetworkManager version. Used for --sysroot.

DRACUT_INSTALL_PATH

overrides PATH environment for dracut-install to look for binaries relative to --sysroot. In a cross-compiled environment (e.g. Yocto), PATH points to natively built binaries that are not in the host’s /bin, /usr/bin, etc. dracut-install still needs plain /bin and /usr/bin that are relative to the cross-compiled sysroot.

Default: PATH

DRACUT_INSTALL_LOG_TARGET

overrides DRACUT_LOG_TARGET for dracut-install. It allows running dracut-install* to run with different log target that dracut** runs with.

Default: DRACUT_LOG_TARGET

DRACUT_INSTALL_LOG_LEVEL

overrides DRACUT_LOG_LEVEL for dracut-install. It allows running dracut-install* to run with different log level that dracut** runs with.

Default: DRACUT_LOG_LEVEL

/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

/usr/lib/dracut/dracut.conf.d/*.conf

see dracut.conf5

The dracut command is part of the dracut package and is available from https://github.com/dracut-ng/dracut-ng

Harald Hoyer

Victor Lowther

Amadeusz Żołnowski

Hannes Reinecke

Daniel Molkentin

Will Woods

Philippe Seewer

Warren Togami

dracut.cmdline(7) dracut.conf(5) lsinitrd(1)

dracut.bootup(7), dracut-catimages(8), dracut.cmdline(7), dracut-cmdline.service(8), dracut.conf(5), dracut-initqueue.service(8), dracut.modules(7), dracut-mount.service(8), dracut-pre-mount.service(8), dracut-pre-pivot.service(8), dracut-pre-trigger.service(8), dracut-pre-udev.service(8), dracut-shutdown.service(8), lsinitrd(1), mkbootdisk(8), mkdumprd(8), systemd-network-generator.service(8), systemtap-service(8), virt-resize(1).