|
HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | SYNOPSIS | DESCRIPTION | USAGE | TROUBLESHOOTING | OPTIONS | ENVIRONMENT | FILES | AVAILABILITY | AUTHORS | SEE ALSO | COLOPHON |
|
|
|
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, 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/initramfs-<kernel-version>.img.
dracut creates an initial image used by the kernel for preloading
the block device modules (such as IDE, SCSI or RAID) which are
needed to access the root filesystem, mounting the root
filesystem and booting into the real system.
At boot time, the kernel unpacks that archive into RAM disk,
mounts and uses it as initial root file system. All finding of
the root device happens in this early userspace.
Initramfs images are also called "initrd".
For a complete list of kernel command line options see
dracut.cmdline(7).
If you are dropped to an emergency shell, while booting your
initramfs, the file /run/initramfs/rdsosreport.txt is created,
which can be saved to a (to be mounted by hand) partition
(usually /boot) or a USB stick. Additional debugging info can be
produced by adding rd.debug to the kernel command line.
/run/initramfs/rdsosreport.txt contains all logs and the output
of some tools. It should be attached to any report about dracut
problems.
To create a initramfs image, the most simple command is:
# dracut
This will generate a general purpose initramfs image, with all
possible functionality resulting of the combination of the
installed dracut modules and system tools. The image, 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/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.
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.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.
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.
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:
• 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 the section called “All bug reports”,
include the following information:
• 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:
• 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 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. 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-existent
or empty.
--no-uefi
Disables UEFI mode.
--no-machineid
Affects the default output filename of --uefi and will
discard the <MACHINE_ID> part.
--uefi-stub <file>
Specifies the UEFI stub loader, which will load the attached
kernel, initramfs and kernel command line and boots the
kernel. The default is
$prefix/lib/systemd/boot/efi/linux<EFI-MACHINE-TYPE-NAME>.efi.stub.
--uefi-splash-image <file>
Specifies the UEFI stub loader’s splash image. Requires
bitmap (.bmp) image format.
--kernel-image <file>
Specifies the kernel image, which to include in the UEFI
executable. The default is
/lib/modules/<KERNEL-VERSION>/vmlinuz or
/boot/vmlinuz-<KERNEL-VERSION>.
--sbat <parameters>
Specifies the SBAT parameters, which to include in the UEFI
executable. By default the default SBAT string added is
"sbat,1,SBAT Version,sbat,1,
https://github.com/rhboot/shim/blob/main/SBAT.md ".
--enhanced-cpio
Attempt to use the dracut-cpio binary, which optimizes
archive creation for copy-on-write filesystems by using the
copy_file_range(2) syscall via Rust’s io::copy(). When
specified, initramfs archives are also padded to ensure
optimal data alignment for extent sharing. To retain reflink
data deduplication benefits, this should be used alongside
the --no-compress and --nostrip parameters, with initramfs
source files, --tmpdir staging area and destination all on
the same copy-on-write capable filesystem.
INITRD_COMPRESS
sets the default compression program. See --compress.
DRACUT_LDCONFIG
sets the ldconfig program path and options. Optional. Used
for --sysroot.
Default: ldconfig
DRACUT_LDD
sets the ldd program path and options. Optional. Used for
--sysroot.
Default: ldd
DRACUT_TESTBIN
sets the initially tested binary for detecting library paths.
Optional. Used for --sysroot. In the cross-compiled sysroot,
the default value (/bin/sh) is unusable, as it is an absolute
symlink and points outside the sysroot directory.
Default: /bin/sh
DRACUT_INSTALL
overrides path and options for executing dracut-install
internally. Optional. Can be used to debug dracut-install
while running the main dracut script.
Default: dracut-install
Example: DRACUT_INSTALL="valgrind dracut-install"
DRACUT_COMPRESS_BZIP2, DRACUT_COMPRESS_LBZIP2,
DRACUT_COMPRESS_LZMA, DRACUT_COMPRESS_XZ, DRACUT_COMPRESS_GZIP,
DRACUT_COMPRESS_PIGZ, DRACUT_COMPRESS_LZOP, DRACUT_COMPRESS_ZSTD,
DRACUT_COMPRESS_LZ4, DRACUT_COMPRESS_CAT
overrides for compression utilities to support using them
from non-standard paths.
Default values are the default compression utility names to
be found in PATH.
DRACUT_ARCH
overrides the value of uname -m. Used for --sysroot.
Default: empty (the value of uname -m on the host system)
SYSTEMD_VERSION
overrides systemd version. Used for --sysroot.
SYSTEMCTL
overrides the systemctl binary. Used for --sysroot.
NM_VERSION
overrides the NetworkManager version. Used for --sysroot.
DRACUT_INSTALL_PATH
overrides PATH environment for dracut-install to look for
binaries relative to --sysroot. In a cross-compiled
environment (e.g. Yocto), PATH points to natively built
binaries that are not in the host’s /bin, /usr/bin, etc.
dracut-install still needs plain /bin and /usr/bin that are
relative to the cross-compiled sysroot.
Default: PATH
DRACUT_INSTALL_LOG_TARGET
overrides DRACUT_LOG_TARGET for dracut-install. It allows
running dracut-install* to run with different log target that
dracut** runs with.
Default: DRACUT_LOG_TARGET
DRACUT_INSTALL_LOG_LEVEL
overrides DRACUT_LOG_LEVEL for dracut-install. It allows
running dracut-install* to run with different log level that
dracut** runs with.
Default: DRACUT_LOG_LEVEL
/var/log/dracut.log
logfile of initramfs image creation
/tmp/dracut.log
logfile of initramfs image creation, if /var/log/dracut.log
is not writable
/etc/dracut.conf
see dracut.conf5
/etc/dracut.conf.d/*.conf
see dracut.conf5
/usr/lib/dracut/dracut.conf.d/*.conf
see dracut.conf5
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/dracutdevs/dracut
Harald Hoyer
Victor Lowther
Amadeusz Żołnowski
Hannes Reinecke
Daniel Molkentin
Will Woods
Philippe Seewer
Warren Togami
dracut.cmdline(7) dracut.conf(5) lsinitrd(1)
This page is part of the dracut (event driven initramfs
infrastructure) project. Information about the project can be
found at ⟨https://dracut.wiki.kernel.org/index.php/Main_Page⟩.
If you have a bug report for this manual page, send it to
initramfs@vger.kernel.org. This page was obtained from the
project's upstream Git repository
⟨https://github.com/dracutdevs/dracut.git⟩ on 2024-06-14. (At
that time, the date of the most recent commit that was found in
the repository was 2024-03-21.) 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
man-pages@man7.org
dracut 059-204-g6acfecae 09/13/2023 DRACUT(8)
Pages that refer to this page: lsinitrd(1), dracut.conf(5), dracut.bootup(7), dracut.cmdline(7), dracut.modules(7), dracut-catimages(8), systemd-network-generator.service(8), systemtap-service(8)
|
HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|