x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
DRACUT(8) dracut DRACUT(8)
NAME
dracut - low-level tool for generating an initramfs/initrd 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,
depending on bootloader specification, the default location can be
/efi/<machine-id>/<kernel-version>/initrd,
/boot/<machine-id>/<kernel-version>/initrd,
/boot/efi/<machine-id>/<kernel-version>/initrd,
/lib/modules/<kernel-version>/initrd or /boot/initrd-<kernel-version>.
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, depending on bootloader
specification, can be /efi/<machine-id>/<kernel-version>/initrd,
/boot/<machine-id>/<kernel-version>/initrd,
/boot/efi/<machine-id>/<kernel-version>/initrd,
/lib/modules/<kernel-version>/initrd or /boot/initrd-<kernel-version>,
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.
Inspecting the Contents
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
Adding dracut Modules
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 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
Omitting dracut Modules
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 dracut.conf(5)),
or use the -o or --omit option on the command line:
# dracut -o "multipath lvm" no-multipath-lvm.img
Adding Kernel Modules
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 dracut.conf(5)):
# dracut --add-drivers mymod initramfs-with-mymod.img
Boot parameters
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.
The kernel command line can also be provided by the dhcp server with
the root-path option. See the section called "Network Boot".
For a full reference of all kernel command line parameters, see
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 the section called
"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.
Injecting custom Files
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. --include
can only be specified once.
# 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.ext3 ssh' initramfs-dbg.img
This will create an initramfs with the strace, fsck.ext3 and ssh
executables, together with the libraries needed to start those. The
--install option can be specified multiple times.
Network Boot
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 the section
called "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.
TROUBLESHOOTING
If the boot process does not succeed, you have several options to debug
the situation.
Identifying your problem area
1. Remove 'rhgb' 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.
Information to include in your report
All bug reports
In all cases, the following should be mentioned and attached to
your bug report:
o The exact kernel command-line used. Typically from the
bootloader configuration file (e.g. /boot/grub2/grub.cfg) or
from /proc/cmdline.
o A copy of your disk partition information from /etc/fstab,
which might be obtained booting an old working initramfs or a
rescue medium.
o Turn on dracut debugging (see the debugging dracut section),
and attach the file /run/initramfs/rdsosreport.txt.
o 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 the section called "All bug reports", include the
following information:
o Please include the output of
# /sbin/ifup <interfacename>
# ip addr show
Debugging dracut
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 'rhgb' 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 the section called "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:
o A block device (e.g. /dev/sda7)
o A LVM logical volume (e.g. /dev/VolGroup00/LogVol00)
o An encrypted device (e.g.
/dev/mapper/luks-4d5972ea-901c-4584-bd75-1da802417d83)
o 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="ext3"
/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 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.
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.
<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.
--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-existant 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>.
--check-supported
The kernel may be configured to check whether a module is supported
by the vendor before allowing it to be loaded. On these systems,
it's possible to generate an initramfs image that will fail to boot
due to unsupported modules being refused. This option enables a
check that will issue a warning if a module built without the
support option enabled is encountered while building the image. Use
of this option assumes that the kernel requires supported modules
and will issue a warning on every module if used otherwise.
--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.
ENVIRONMENT
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
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
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.
AVAILABILITY
The dracut command is part of the dracut package and is available from
https://github.com/dracutdevs/dracut
AUTHORS
Harald Hoyer
Victor Lowther
Amadeusz olnowski
Hannes Reinecke
Daniel Molkentin
Will Woods
Philippe Seewer
Warren Togami
SEE ALSO
dracut.cmdline(7) dracut.conf(5) lsinitrd(1)
dracut 03/07/2025 DRACUT(8)
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