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DRACUT(8) dracut DRACUT(8)
dracut - low-level tool for generating an initramfs/initrd image
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
man: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.
Dracut is expected to run as the root user to have unrestricted
access to the root filesystem during initramfs generation. Running
dracut as any user other than root supports only a limited set of
functionalities. As an example, to facilitate secure sulogin in
the emergency console with the host password requires read access
to /etc/shadow on the host, which is usually only allowed for the
root user.
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.
To see the contents of the image created by dracut, you can use
the lsinitrd tool.
# lsinitrd | less
To display the contents of a file in the initramfs also use the
lsinitrd tool:
# lsinitrd -f /etc/ld.so.conf
include ld.so.conf.d/*.conf
Some dracut modules are turned off by default and have to be
activated manually. You can do this by adding the dracut modules
to the configuration file /etc/dracut.conf or
/etc/dracut.conf.d/myconf.conf. See man:dracut.conf[5] You can
also add dracut modules on the command line by using the -a or
--add option:
# dracut --add module initramfs-module.img
To see a list of available dracut modules, use the --list-modules
option:
# dracut --list-modules
Tip
Omitted modules will override added modules. --force-add can
be used to add a module in host-only mode if it is specified
as omitted (usually via a distribution configuration file).
Sometimes you don’t want a dracut module to be included for
reasons of speed, size or functionality. To do this, either
specify the omit_dracutmodules variable in the dracut.conf or
/etc/dracut.conf.d/myconf.conf configuration file (see
man:dracut.conf[5]) or use the -o or --omit option on the command
line:
# dracut -o "multipath lvm" no-multipath-lvm.img
If you need a special kernel module in the initramfs, which is not
automatically picked up by dracut, you have the use the
--add-drivers option on the command line or the drivers variable
in the /etc/dracut.conf or /etc/dracut.conf.d/myconf.conf
configuration file (see man:dracut.conf[5]):
# dracut --add-drivers mymod initramfs-with-mymod.img
An initramfs generated without the "hostonly" mode, does not
contain any system configuration files (except for some special
exceptions), so the configuration has to be done on the kernel
command line. With this flexibility, you can easily boot from a
changed root partition, without the need to recompile the
initramfs image. So, you could completely change your root
partition (move it inside a md raid with encryption and LVM on
top), as long as you specify the correct filesystem LABEL or UUID
on the kernel command line for your root device, dracut will find
it and boot from it.
Files from the host root filesystem under the /etc, /var, or /run
directories should only be copied over to the generated initramfs
in "hostonly" mode, as these host directories are meant to be
customized by users for each host. Only host files from the /usr
directory in the host root filesystem are meant to be included in
the generated initramfs in both "hostonly" and "non-hostonly"
mode. As an example /etc/fstab and /etc/cryptab files should be
only consulted when dracut is run in "hostonly" mode.
The only exception to this rule is the /etc/dracut.conf file and
/etc/dracut.conf.d/ directory that is considered both in
"hostonly" and "non-hostonly" modes.
Some command line arguments (e.g. --include) can override the
default "hostonly"/"non-hostonly" modes.
Generic initrd’s are larger, but should be able to automatically
boot any bootable configuration with appropriate boot flags (root
device, network configuration information, etc.)
The kernel command line can also be provided by the dhcp server
with the root-path option. See NETWORK BOOT.
For a full reference of all kernel command line parameters, see
man:dracut.cmdline[7].
To get a quick start for the suitable kernel command line on your
system, use the --print-cmdline option:
# dracut --print-cmdline
root=UUID=8b8b6f91-95c7-4da2-831b-171e12179081 rootflags=rw,relatime,discard,data=ordered rootfstype=ext4
Specifying the root Device
This is the only option dracut really needs to boot from your root
partition. Because your root partition can live in various
environments, there are a lot of formats for the root= option. The
most basic one is root=<path to device node>:
root=/dev/sda2
Because device node names can change, dependent on the drive
ordering, you are encouraged to use the filesystem identifier
(UUID) or filesystem label (LABEL) to specify your root partition:
root=UUID=19e9dda3-5a38-484d-a9b0-fa6b067d0331
or
root=LABEL=myrootpartitionlabel
To see all UUIDs or LABELs on your system, do:
# ls -l /dev/disk/by-uuid
or
# ls -l /dev/disk/by-label
If your root partition is on the network see NETWORK BOOT.
Keyboard Settings
If you have to input passwords for encrypted disk volumes, you
might want to set the keyboard layout and specify a display font.
A typical german kernel command line would contain:
rd.vconsole.font=eurlatgr rd.vconsole.keymap=de-latin1-nodeadkeys rd.locale.LANG=de_DE.UTF-8
Setting these options can override the setting stored on your
system, if you use a modern init system, like systemd.
Blacklisting Kernel Modules
Sometimes it is required to prevent the automatic kernel module
loading of a specific kernel module. To do this, just add
rd.driver.blacklist=<kernel module name>, with <kernel module
name> not containing the .ko suffix, to the kernel command line.
For example:
rd.driver.blacklist=mptsas rd.driver.blacklist=nouveau
The option can be specified multiple times on the kernel command
line.
Speeding up the Boot Process
If you want to speed up the boot process, you can specify as much
information for dracut on the kernel command as possible. For
example, you can tell dracut, that you root partition is not on a
LVM volume or not on a raid partition, or that it lives inside a
specific crypto LUKS encrypted volume. By default, dracut searches
everywhere. A typical dracut kernel command line for a plain
primary or logical partition would contain:
rd.luks=0 rd.lvm=0 rd.md=0 rd.dm=0
This turns off every automatic assembly of LVM, MD raids, DM raids
and crypto LUKS.
Of course, you could also omit the dracut modules in the initramfs
creation process, but then you would lose the possibility to turn
it on on demand.
To add your own files to the initramfs image, you have several
possibilities.
The --include option let you specify a source path and a target
path. For example
# dracut --include cmdline-preset /etc/cmdline.d/mycmdline.conf initramfs-cmdline-pre.img
will create an initramfs image, where the file cmdline-preset will
be copied inside the initramfs to /etc/cmdline.d/mycmdline.conf.
# 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
This will put the contents of the rd.live.overlay directory into
the root of the initramfs image.
The --install option let you specify several files, which will get
installed in the initramfs image at the same location, as they are
present on initramfs creation time.
# dracut --install 'strace fsck.ext4 ssh' initramfs-dbg.img
This will create an initramfs with the strace, fsck.ext4 and ssh
executables, together with the libraries needed to start those.
The --install option can be specified multiple times.
If your root partition is on a network drive, you have to have the
network dracut modules installed to create a network aware
initramfs image.
If you specify ip=dhcp on the kernel command line, then dracut
asks a dhcp server about the ip address for the machine. The dhcp
server can also serve an additional root-path, which will set the
root device for dracut. With this mechanism, you have static
configuration on your client machine and a centralized boot
configuration on your TFTP/DHCP server. If you can’t pass a kernel
command line, then you can inject /etc/cmdline.d/mycmdline.conf,
with a method described in INJECTING CUSTOM FILES.
Reducing the Image Size
To reduce the size of the initramfs, you should create it with by
omitting all dracut modules, which you know, you don’t need to
boot the machine.
You can also specify the exact dracut and kernel modules to
produce a very tiny initramfs image.
For example for a NFS image, you would do:
# dracut -m "nfs network base" initramfs-nfs-only.img
Then you would boot from this image with your target machine and
reduce the size once more by creating it on the target machine
with the --host-only option:
# dracut -m "nfs network base" --host-only initramfs-nfs-host-only.img
This will reduce the size of the initramfs image significantly.
If the boot process does not succeed, you have several options to
debug the situation.
1. Remove 'splash' and 'quiet' from the kernel command line
2. Add 'rd.shell' to the kernel command line. This will present a
shell should dracut be unable to locate your root device
3. Add 'rd.shell rd.debug log_buf_len=1M' to the kernel command
line so that dracut shell commands are printed as they are
executed
4. The file /run/initramfs/rdsosreport.txt is generated, which
contains all the logs and the output of all significant tools,
which are mentioned later.
If you want to save that output, simply mount /boot by hand or
insert an USB stick and mount that. Then you can store the output
for later inspection.
All bug reports
In all cases, the following should be mentioned and attached to
your bug report:
• The exact kernel command-line used. Typically from the
bootloader configuration file (e.g. /boot/grub2/grub.cfg) or
from /proc/cmdline.
• A copy of your disk partition information from /etc/fstab,
which might be obtained booting an old working initramfs or a
rescue medium.
• Turn on dracut debugging (see the debugging dracut section),
and attach the file /run/initramfs/rdsosreport.txt.
• If you use a dracut configuration file, please include
/etc/dracut.conf and all files in /etc/dracut.conf.d/*.conf
Network root device related problems
This section details information to include when experiencing
problems on a system whose root device is located on a network
attached volume (e.g. iSCSI, NFS or NBD). As well as the
information from All bug reports, include the following
information:
• Please include the output of
# /sbin/ifup <interfacename>
# ip addr show
Configure a serial console
Successfully debugging dracut will require some form of console
logging during the system boot. This section documents configuring
a serial console connection to record boot messages.
1. First, enable serial console output for both the kernel and
the bootloader.
2. Open the file /boot/grub2/grub.cfg for editing. Below the line
'timeout=5', add the following:
serial --unit=0 --speed=9600
terminal --timeout=5 serial console
3. Also in /boot/grub2/grub.cfg, add the following boot arguments
to the 'kernel' line:
console=tty0 console=ttyS0,9600
4. When finished, the /boot/grub2/grub.cfg file should look
similar to the example below.
default=0
timeout=5
serial --unit=0 --speed=9600
terminal --timeout=5 serial console
title Fedora (2.6.29.5-191.fc11.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 console=ttyS0,9600
initrd /dracut-2.6.29.5-191.fc11.x86_64.img
5. More detailed information on how to configure the kernel for
console output can be found at
http://www.faqs.org/docs/Linux-HOWTO/Remote-Serial-Console-HOWTO.html#CONFIGURE-KERNEL.
6. Redirecting non-interactive output
Note
You can redirect all non-interactive output to /dev/kmsg
and the kernel will put it out on the console when it
reaches the kernel buffer by doing
# exec >/dev/kmsg 2>&1 </dev/console
Using the dracut shell
dracut offers a shell for interactive debugging in the event
dracut fails to locate your root filesystem. To enable the shell:
1. Add the boot parameter 'rd.shell' to your bootloader
configuration file (e.g. /boot/grub2/grub.cfg)
2. Remove the boot arguments 'splash' and 'quiet'
A sample /boot/grub2/grub.cfg bootloader configuration file is
listed below.
default=0
timeout=5
serial --unit=0 --speed=9600
terminal --timeout=5 serial console
title Fedora (2.6.29.5-191.fc11.x86_64)
root (hd0,0)
kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 rd.shell
initrd /dracut-2.6.29.5-191.fc11.x86_64.img
3. If system boot fails, you will be dropped into a shell as seen
in the example below.
No root device found
Dropping to debug shell.
#
4. Use this shell prompt to gather the information requested
above (see All bug reports).
Accessing the root volume from the dracut shell
From the dracut debug shell, you can manually perform the task of
locating and preparing your root volume for boot. The required
steps will depend on how your root volume is configured. Common
scenarios include:
• A block device (e.g. /dev/sda7)
• A LVM logical volume (e.g. /dev/VolGroup00/LogVol00)
• An encrypted device (e.g.
/dev/mapper/luks-4d5972ea-901c-4584-bd75-1da802417d83)
• A network attached device (e.g.
netroot=iscsi:@192.168.0.4::3260::iqn.2009-02.org.example:for.all)
The exact method for locating and preparing will vary. However, to
continue with a successful boot, the objective is to locate your
root volume and create a symlink /dev/root which points to the
file system. For example, the following example demonstrates
accessing and booting a root volume that is an encrypted LVM
Logical volume.
1. Inspect your partitions using parted
# parted /dev/sda -s p
Model: ATA HTS541060G9AT00 (scsi)
Disk /dev/sda: 60.0GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Number Start End Size Type File system Flags
1 32.3kB 10.8GB 107MB primary ext4 boot
2 10.8GB 55.6GB 44.7GB logical lvm
2. You recall that your root volume was a LVM logical volume.
Scan and activate any logical volumes.
# lvm vgscan
# lvm vgchange -ay
3. You should see any logical volumes now using the command
blkid:
# blkid
/dev/sda1: UUID="3de247f3-5de4-4a44-afc5-1fe179750cf7" TYPE="ext4"
/dev/sda2: UUID="Ek4dQw-cOtq-5MJu-OGRF-xz5k-O2l8-wdDj0I" TYPE="LVM2_member"
/dev/mapper/linux-root: UUID="def0269e-424b-4752-acf3-1077bf96ad2c" TYPE="crypto_LUKS"
/dev/mapper/linux-home: UUID="c69127c1-f153-4ea2-b58e-4cbfa9257c5e" TYPE="ext4"
/dev/mapper/linux-swap: UUID="47b4d329-975c-4c08-b218-f9c9bf3635f1" TYPE="swap"
4. From the output above, you recall that your root volume exists
on an encrypted block device. Following the guidance disk
encryption guidance from the Installation Guide, you unlock
your encrypted root volume.
# UUID=$(cryptsetup luksUUID /dev/mapper/linux-root)
# cryptsetup luksOpen /dev/mapper/linux-root luks-$UUID
Enter passphrase for /dev/mapper/linux-root:
Key slot 0 unlocked.
5. Next, make a symbolic link to the unlocked root volume
# ln -s /dev/mapper/luks-$UUID /dev/root
6. With the root volume available, you may continue booting the
system by exiting the dracut shell
# exit
Additional dracut boot parameters
For more debugging options, see man:dracut.cmdline[7].
Debugging dracut on shutdown
To debug the shutdown sequence on systemd systems, you can
rd.break on pre-shutdown or shutdown.
To do this from an already booted system:
# 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
This will give you a dracut shell after the system pivot’ed back
in the initramfs.
--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. If a module appears in both add and omit
lists, it will be omitted. 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>
A space-separated list of dracut modules appended to the
default set of modules when host-only (-H) mode is specified.
Unlike --add, --force-add will override omittied (-o) modules;
it is thus useful to ensure that a module is added even if it
is specified as omitted in configuration files. 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. Warning: Avoid manually
omitting dracut modules, as you may inadvertently remove
essential ones that dracut can’t detect or warn you about.
Using this option is not recommended and is at your own risk.
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. This option is not recommended to use
(use at your own risk).
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. This option forces dracut to only
include the specified kernel modules. In most cases the
"--add-drivers" option is what you want to use. This option is
not recommended to use (use at your own risk).
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 part of the kernel command line required to boot for the
current disk layout. This option does not return all kernel
command line options that dracut might add to the initrd.
--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
--add-confdir <configuration directory>
Add an extra configuration directory to use *.conf files from.
If the directory is not existed, will look for subdirectory
under confdir.
Default: empty
--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 files from the host root filesystem,
including from directories that are customized by system
administrators and users such as /etc and generate
host-specific configuration (default). Resilience to minor
hardware changes of the generated initramfs is controlled by
hostonly-mode .
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" ...
--remove <file/dir list>
Remove a space-separated list of files and directories from
the initramfs.
--install-optional <file list>
Install the space separated list of files into the initramfs,
if they exist.
--gzip
Compress the generated initramfs using gzip.
Warning
Make sure your kernel has gzip decompression support
compiled in, otherwise you will not be able to boot.
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
man: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
PKG_CONFIG
sets the pkg-config program path and options. Optional. Most
useful together with --sysroot.
Default: pkg-config
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
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. Deprecated,
better use /etc/cmdline.d/*.conf.
/etc/cmdline.d/*.conf
Can contain additional command line options.
The dracut command is part of the dracut package and is available
from https://github.com/dracut-ng/dracut-ng ""
<"https://github.com/dracut-ng/dracut-ng">
Harald Hoyer
Victor Lowther
Amadeusz Żołnowski
Hannes Reinecke
Daniel Molkentin
Will Woods
Philippe Seewer
Warren Togami
man:dracut.cmdline[7] man:dracut.conf[5] man:lsinitrd[1].SH
COLOPHON This page is part of the dracut (event driven initramfs
infrastructure) project. Information about the project can be
found at ⟨https://github.com/dracut-ng//dracut-ng⟩. If you have a
bug report for this manual page, see
⟨https://github.com/dracut-ng/dracut-ng/issues⟩. This page was
obtained from the project's upstream Git repository
⟨https://github.com/dracut-ng/dracut-ng.git⟩ on 2025-08-11. (At
that time, the date of the most recent commit that was found in
the repository was 2025-08-09.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
dracut 2025-08-09 DRACUT(8)
Pages that refer to this page: lsinitrd(1), dracut.bootup(7), dracut-catimages(8), systemd-network-generator.service(8), systemtap-service(8)
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