dracut

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.

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.

Usage

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 --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. The usage of the --hostonly 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.

# lsinitrd | less

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

# dracut --add bootchart initramfs-bootchart.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.ext3 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

Troubleshooting

If the boot process does not succeed, you have several options to debug the situation. Some of the basic operations are covered here. For more information you should also visit: https://www.kernel.org/pub/linux/utils/boot/dracut/dracut.html

# 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

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.

-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"  ...

-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"  ...

-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 [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 [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"  ...

--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 [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 [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-cmdline <parameters>

specify default kernel command line 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

--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 (default)

--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))

-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.

--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-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.

--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"

--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 hostonly 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 [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"

--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 "lzma --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 "lzma --compress=xz --check=crc32 --lzma2=dict=1MiB"

--lzo

Compress the generated initramfs using lzop.

--lz4

Compress the generated initramfs using lz4.

--zstd

Compress the generated initramfs using Zstandard.

--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.

--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.

--loginstall <DIR>

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

--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-existant or empty.

--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 or $prefix/lib/gummiboot/linux<EFI-MACHINE-TYPE-NAME>.efi.stub

--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>

Environment

INITRD_COMPRESS

sets the default compression program. See --compress.

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

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

see dracut.conf5

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) lsinitrd(1)

Referenced By

bootup(7), 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), mkinitrd(8), new-kernel-pkg(8), systemtap-service(8), virt-resize(1).