dracut.cmdline(7) — Arch manual pages

dracut.cmdline(7) — Arch manual pages
DRACUT.CMDLINE(7)
dracut
DRACUT.CMDLINE(7)
NAME
dracut.cmdline - dracut kernel command line options
DESCRIPTION
The root device used by the kernel is specified in the boot
configuration file on the kernel command line, as always.
The traditional
root=/dev/sda1
style device specification
is allowed, but not encouraged. The root device should better be identified
by LABEL or UUID. If a label is used, as in
root=LABEL=
the initramfs will search all
available devices for a filesystem with the appropriate label, and mount
that device as the root filesystem.
root=UUID=
will
mount the partition with that UUID as the root filesystem.
In the following all kernel command line parameters, which are
processed by dracut, are described.
"rd.*" parameters mentioned without "=" are
boolean parameters. They can be turned on/off by setting them to {0|1}. If
the assignment with "=" is missing "=1" is implied. For
example
rd.info
can be turned off with
rd.info=0
or turned on
with
rd.info=1
or
rd.info
. The last value in the kernel
command line is the value, which is honored.
Standard
init=

specify the path to the init program to be started after
the initramfs has finished
root=

specify the block device to use as the root filesystem.
Example
root=/dev/sda1
root=/dev/disk/by-path/pci-0000:00:1f.1-scsi-0:0:1:0-part1
root=/dev/disk/by-label/Root
root=LABEL=Root
root=/dev/disk/by-uuid/3f5ad593-4546-4a94-a374-bcfb68aa11f7
root=UUID=3f5ad593-4546-4a94-a374-bcfb68aa11f7
root=PARTUUID=3f5ad593-4546-4a94-a374-bcfb68aa11f7
rootfstype=

"auto" if not specified.
Example
rootfstype=ext4
rootflags=

specify additional mount options for the root filesystem.
If not set,
/etc/fstab
of the real root will be parsed for special
mount options and mounted accordingly.
ro
force mounting
and
/usr
(if it is a
separate device) read-only. If none of ro and rw is present, both are mounted
according to
/etc/fstab
rw
force mounting
and
/usr
(if it is a
separate device) read-write. See also ro option.
rootfallback=

specify the block device to use as the root filesystem,
if the normal root cannot be found. This can only be a simple block device
with a simple file system, for which the filesystem driver is either compiled
in, or added manually to the initramfs. This parameter can be specified
multiple times.
rd.auto
rd.auto=1
enable autoassembly of special devices like cryptoLUKS,
dmraid, mdraid or lvm. Default is off as of dracut version >= 024.
rd.hostonly=0
removes all compiled in configuration of the host system
the initramfs image was built on. This helps booting, if any disk layout
changed, especially in combination with rd.auto or other parameters specifying
the layout.
rd.cmdline=ask
prompts the user for additional kernel command line
parameters
rd.fstab=0
do not honor special mount options for the root
filesystem found in
/etc/fstab
of the real root.
resume=

resume from a swap partition
Example
resume=/dev/disk/by-path/pci-0000:00:1f.1-scsi-0:0:1:0-part1
resume=/dev/disk/by-uuid/3f5ad593-4546-4a94-a374-bcfb68aa11f7
resume=UUID=3f5ad593-4546-4a94-a374-bcfb68aa11f7
rd.skipfsck
skip fsck for rootfs and
/usr
. If you’re
mounting
/usr
read-only and the init system performs fsck before
remount, you might want to use this option to avoid duplication.
iso-scan/filename
Mount all mountable devices and search for ISO pointed by the
argument. When the ISO is found set it up as a loop device. Device
containing this ISO image will stay mounted at /run/initramfs/isoscandev.
Using iso-scan/filename with a Fedora/Red Hat/CentOS Live iso should just
work by copying the original kernel cmdline parameters. Requires the dracut
dmsquash-live
module.
Example
menuentry 'Live' --class gnu-linux --class gnu --class os {
set isolabel=Live-x86_64
set isofile="/boot/iso/Live-x86_64.iso"
loopback loop $isofile
linux (loop)/isolinux/vmlinuz0 boot=isolinux iso-scan/filename=$isofile root=live:LABEL=$isolabel ro rd.live.image quiet
initrd (loop)/isolinux/initrd0.img
Misc
rd.emergency=
[reboot|poweroff|halt]
specify, what action to execute in case of a critical
failure. rd.shell=0 must also be specified.
rd.driver.blacklist=

[,

,...]
do not load kernel module . This
parameter can be specified multiple times.
rd.driver.pre=

[,

,...]
force loading kernel module . This
parameter can be specified multiple times.
rd.driver.post=

[,

,...]
force loading kernel module after all
automatic loading modules have been loaded. This parameter can be specified
multiple times.
rd.driver.export
making all drivers from initramfs available to rootfs
after switch_root. This parameter can be set to
force
for exporting
over existing modules. Requires the dracut
kernel-modules-export
module.
rd.retry=

specify how long dracut should retry the initqueue to
configure devices. The default is 180 seconds. After 2/3 of the time, degraded
raids are force started. If you have hardware, which takes a very long time to
announce its drives, you might want to extend this value. Requires the dracut
initqueue
module.
rd.timeout=

specify how long dracut should wait for devices to
appear. The default is
, which means
forever
. Note that this
timeout should be longer than rd.retry to allow for proper
configuration.
rd.noverifyssl
accept self-signed certificates for ssl downloads.
Requires the dracut
url-lib
module.
rd.ctty=

specify the controlling terminal for the console. This is
useful, if you have multiple "console=" arguments.
rd.shutdown.timeout.umount=

specify how long dracut should wait for an individual
umount to finish during shutdown. This avoids the system from blocking when
unmounting a file system cannot complete and waits indefinitely. Value
means to wait
forever
. The default is 90 seconds. Requires the
dracut
shutdown
module.
Debug
If you are dropped to an emergency shell, 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.
rd.info
print informational output though "quiet" is
set
rd.shell
allow dropping to a shell, if root mounting fails
rd.debug
set -x for the dracut shell. If systemd is active in the
initramfs, all output is logged to the systemd journal, which you can inspect
with "journalctl -ab". If systemd is not active, the logs are
written to dmesg and
/run/initramfs/init.log
. If "quiet" is
set, it also logs to the console.
rd.memdebug=[0-5]
Print memory usage info at various points, set the
verbose level from 0 to 5.
Higher level means more debugging output:
0 - no output
1 - partial /proc/meminfo
2 - /proc/meminfo
3 - /proc/meminfo + /proc/slabinfo
4 - /proc/meminfo + /proc/slabinfo + memstrack summary
NOTE: memstrack is a memory tracing tool that tracks the total memory
consumption, and peak memory consumption of each kernel modules
and userspace progress during the whole initramfs runtime, report
is generated and the end of initramfs run.
5 - /proc/meminfo + /proc/slabinfo + memstrack (with top memory stacktrace)
NOTE: memstrack (with top memory stacktrace) will print top memory
allocation stack traces during the whole initramfs runtime.
rd.break
drop to a shell at the end
rd.break=
{cmdline|pre-udev|pre-trigger|initqueue|pre-mount|mount|pre-pivot|cleanup}
drop to a shell before the defined breakpoint starts.
This parameter can be specified multiple times.
rd.udev.log_level=
{err|info|debug}
set udev log level. The default is
err
I18N
Requires the dracut
i18n
module.
rd.vconsole.keymap=

keyboard translation table loaded by loadkeys; taken from
keymaps directory; will be written as KEYMAP to
/etc/vconsole.conf
in
the initramfs.
Example
rd.vconsole.keymap=de-latin1-nodeadkeys
rd.vconsole.keymap.ext=
names>
list of extra keymaps to bo loaded (sep. by space); will
be written as EXT_KEYMAP to
/etc/vconsole.conf
in the initramfs
rd.vconsole.unicode
boolean, indicating UTF-8 mode; will be written as
UNICODE to
/etc/vconsole.conf
in the initramfs
rd.vconsole.font=

console font; taken from consolefonts directory; will be
written as FONT to
/etc/vconsole.conf
in the initramfs.
Example
rd.vconsole.font=eurlatgr
rd.vconsole.font.map=
name>
see description of
-m
parameter in setfont manual;
taken from consoletrans directory; will be written as FONT_MAP to
/etc/vconsole.conf
in the initramfs
rd.vconsole.font.unimap=
name>
see description of
-u
parameter in setfont manual;
taken from unimaps directory; will be written as FONT_UNIMAP to
/etc/vconsole.conf
in the initramfs
rd.locale.LANG=

taken from the environment; if no UNICODE is defined we
set its value in basis of LANG value (whether it ends with ".utf8"
(or similar) or not); will be written as LANG to
/etc/locale.conf
in
the initramfs.
Example
rd.locale.LANG=pl_PL.utf8
rd.locale.LC_ALL=

taken from the environment; will be written as LC_ALL to
/etc/locale.conf
in the initramfs
LVM
Requires the dracut
lvm
module.
rd.lvm=0
disable LVM detection
rd.lvm.vg=

only activate all logical volumes in the the volume
groups with the given name. rd.lvm.vg can be specified multiple times on the
kernel command line.
rd.lvm.lv=
/name>
only activate the logical volumes with the given name.
rd.lvm.lv can be specified multiple times on the kernel command line.
rd.lvm.conf=0
remove any
/etc/lvm/lvm.conf
, which may exist in
the initramfs
crypto LUKS
Requires the dracut
crypt
module.
rd.luks=0
disable crypto LUKS detection
rd.luks.uuid=

only activate the LUKS partitions with the given UUID.
Any "luks-" of the LUKS UUID is removed before comparing to

. The comparisons also matches, if
uuid>
is only the beginning of the LUKS UUID, so you don’t have
to specify the full UUID. This parameter can be specified multiple times.

may be prefixed by the keyword
keysource:
, see
rd.luks.key
below.
rd.luks.allow-discards=

Allow using of discards (TRIM) requests for LUKS
partitions with the given UUID. Any "luks-" of the LUKS UUID is
removed before comparing to

. The comparisons also
matches, if

is only the beginning of the LUKS UUID,
so you don’t have to specify the full UUID. This parameter can be
specified multiple times.
rd.luks.allow-discards
Allow using of discards (TRIM) requests on all LUKS
partitions.
rd.luks.crypttab=0
do not check, if LUKS partition is in
/etc/crypttab
rd.luks.timeout=

specify how long dracut should wait when waiting for the
user to enter the password. This avoid blocking the boot if no password is
entered. It does not apply to luks key. The default is
, which means
forever
crypto LUKS - key on removable device support
NB: If systemd is included in the dracut initrd, dracut’s
built in removable device keying support won’t work. systemd will
prompt for a password from the console even if you’ve supplied
rd.luks.key
. You may be able to use standard systemd
man:fstab[5,external] syntax to get the same effect. If you do need
rd.luks.key
to work, you will have to exclude the "systemd"
dracut module and any modules that depend on it. See man:dracut.conf[5] and
for more
information.
rd.luks.key=
[:[:]]

is the pathname of a key file,
relative to the root of the filesystem on some device. It’s REQUIRED.
When

ends with
.gpg
it’s considered to be
key encrypted symmetrically with GPG. You will be prompted for the GPG
password on boot. GPG support requires the
crypt-gpg
dracut module,
which needs to be added explicitly.

identifies the device on which the key file
resides. It may be the kernel name of the device (should start with
"/dev/"), a UUID (prefixed with "UUID=") or a label
(prefix with "LABEL="). You don’t have to specify a full
UUID. Just its beginning will suffice, even if its ambiguous. All matching
devices will be probed. This parameter is recommended, but not required. If
it’s not present, all block devices will be probed, which may
significantly increase boot time.
If

is given, the specified key will only be
used for the specified LUKS device. Possible values are the same as for

. Unless you have several LUKS devices, you
don’t have to specify this parameter. The simplest usage is:
Example
rd.luks.key=/foo/bar.key
As you see, you can skip colons in such a case.
Note
Your LUKS partition must match your key file.
dracut provides keys to cryptsetup with
-d
(an older alias
for
--key-file
). This uses the entire binary content of the key file
as part of the secret. If you pipe a password into cryptsetup
without
-d
or
--key-file
, it will be treated as text user input, and
only characters before the first newline will be used. Therefore, when
you’re creating an encrypted partition for dracut to mount, and you
pipe a key into
cryptsetup luksFormat
,you must use
-d -
Here is an example for a key encrypted with GPG (warning:
--batch-mode
will overwrite the device without asking for
confirmation):
gpg --quiet --decrypt rootkey.gpg | \
cryptsetup --batch-mode --key-file - \
luksFormat /dev/sda47
If you use unencrypted key files, just use the key file pathname
instead of the standard input. For a random key with 256 bits of entropy,
you might use:
head -32c /dev/urandom > rootkey.key
cryptsetup --batch-mode --key-file rootkey.key \
luksFormat /dev/sda47
You can also use regular key files on an encrypted
keydev
Compared to using GPG encrypted keyfiles on an unencrypted device
this provides the following advantages:
•you can unlock your disk(s) using multiple
passphrases
•better security by not losing the key stretching
mechanism
To use an encrypted
keydev
you
must
ensure that it
becomes available by using the keyword
keysource
e.g.
rd.luks.uuid=keysource:aaaa
aaaa
being
the uuid of the encrypted
keydev
Example:
Lets assume you have three disks
and
with the uuids
aaaa
bbbb
and
cccc
You want to unlock
and
using keyfile
keyfile
The unlocked volumes be
A'
B'
and
C'
with the uuids
AAAA
BBBB
and
CCCC
keyfile
is saved on
C'
as
/keyfile
One luks keyslot of each
and
is setup
with a passphrase.
Another luks keyslot of each
and
is setup with
keyfile
To boot this configuration you could use:
rd.luks.uuid=aaaa
rd.luks.uuid=bbbb
rd.luks.uuid=keysource:cccc
rd.luks.key=/keyfile:UUID=CCCC
Dracut asks for the passphrase for
and uses the keyfile
to unlock
and
If getting the passphrase for
fails it falls back to asking for the
passphrases for
and
If you want
C'
to stay unlocked, specify a luks name for
it, e.g.
rd.luks.name=cccc=mykeys
, otherwise it gets
closed when not needed anymore.
rd.luks.key.tout=0
specify how many times dracut will try to read the keys
specified in rd.luks.key. This gives a chance to the removable device
containing the key to initialize.
MD RAID
Requires the dracut
mdraid
module.
rd.md=0
disable MD RAID detection
rd.md.imsm=0
disable MD RAID for imsm/isw raids, use DM RAID
instead
rd.md.ddf=0
disable MD RAID for SNIA ddf raids, use DM RAID
instead
rd.md.conf=0
ignore mdadm.conf included in initramfs
rd.md.waitclean=1
wait for any resync, recovery, or reshape activity to
finish before continuing
rd.md.uuid=

only activate the raid sets with the given UUID. This
parameter can be specified multiple times.
DM RAID
Requires the dracut
dmraid
module.
rd.dm=0
disable DM RAID detection
rd.dm.uuid=

only activate the raid sets with the given UUID. This
parameter can be specified multiple times.
MULTIPATH
Requires the dracut
multipath
module.
rd.multipath=0
disable multipath detection
rd.multipath=default
use default multipath settings
FIPS
Requires the dracut
fips
module.
rd.fips
enable FIPS
boot=

specify the device, where /boot is located.
Example
boot=/dev/sda1
boot=/dev/disk/by-path/pci-0000:00:1f.1-scsi-0:0:1:0-part1
boot=UUID=
boot=LABEL=
rd.fips.skipkernel
skip checksum check of the kernel image. Useful, if the
kernel image is not in a separate boot partition.
Network
Important
It is recommended to either bind an interface to a MAC with the
ifname
argument, or to use the systemd-udevd predictable network interface names.
Predictable network interface device names based on:
•firmware/bios-provided index numbers for on-board
devices
•firmware-provided pci-express hotplug slot index
number
•physical/geographical location of the
hardware
•the interface’s MAC address
See:
Two character prefixes based on the type of interface:
en
ethernet
wl
wlan
ww
wwan
Type of names:
o
on-board device index number
s[f][d]
hotplug slot index number
x
MAC address
[P]ps[f][d]
PCI geographical location
[P]ps[f][u][..][c][i]
USB port number chain
All multi-function PCI devices will carry the [f]
number in the device name, including the function 0 device.
When using PCI geography, The PCI domain is only prepended when it
is not 0.
For USB devices the full chain of port numbers of hubs is
composed. If the name gets longer than the maximum number of 15 characters,
the name is not exported. The usual USB configuration == 1 and interface ==
0 values are suppressed.
PCI ethernet card with firmware index "1"
•eno1
PCI ethernet card in hotplug slot with firmware index number
•ens1
PCI ethernet multi-function card with 2 ports
•enp2s0f0
•enp2s0f1
PCI wlan card
•wlp3s0
USB built-in 3G modem
•wwp0s29u1u4i6
USB Android phone
•enp0s29u1u2
The following options are supported by the
network-legacy
dracut module. Other network modules might support a slightly different set
of options; refer to the documentation of the specific network module in
use. For NetworkManager, see man:nm-initrd-generator[8].
ip=
{dhcp|on|any|dhcp6|auto6|either6|link6|single-dhcp}
dhcp|on|any
get ip from dhcp server from all interfaces. If
netroot=dhcp, loop sequentially through all interfaces (eth0, eth1, ...) and
use the first with a valid DHCP root-path.
single-dhcp
Send DHCP on all available interfaces in parallel, as
opposed to one after another. After the first DHCP response is received, stop
DHCP on all other interfaces. This gives the fastest boot time by using the IP
on interface for which DHCP succeeded first during early boot. Caveat: Does
not apply to Network Manager.
auto6
IPv6 autoconfiguration
dhcp6
IPv6 DHCP
either6
if auto6 fails, then dhcp6
link6
bring up interface for IPv6 link-local addressing
ip=

{dhcp|on|any|dhcp6|auto6|link6}
[:[

][:

]]
This parameter can be specified multiple times.
dhcp|on|any|dhcp6
get ip from dhcp server on a specific interface
auto6
do IPv6 autoconfiguration
link6
bring up interface for IPv6 link local address

optionally
set
on the
. This cannot be used in conjunction with the
ifname
argument for the same .
ip=

:[

]:




{none|off|dhcp|on|any|dhcp6|auto6|ibft}
[:[

][:

]]
explicit network configuration. If you want do define a
IPv6 address, put it in brackets (e.g. [2001:DB8::1]). This parameter can be
specified multiple times.

is optional and is the address
of the remote endpoint for pointopoint interfaces and it may be followed by a
slash and a decimal number, encoding the network prefix length.

optionally
set
on the
. This cannot be used in conjunction with the
ifname
argument for the same .
ip=

:[

]:




{none|off|dhcp|on|any|dhcp6|auto6|ibft}
[:[

][:

]]
explicit network configuration. If you want do define a
IPv6 address, put it in brackets (e.g. [2001:DB8::1]). This parameter can be
specified multiple times.

is optional and is the address
of the remote endpoint for pointopoint interfaces and it may be followed by a
slash and a decimal number, encoding the network prefix length.
ifname=


Assign network device name (i.e.
"bootnet") to the NIC with MAC .
Warning
Do
not
use the default kernel naming scheme for the
interface name,
as it can conflict with the kernel names. So, don’t use
"eth[0-9]+" for the interface name. Better name it
"bootnet" or "bluesocket".
rd.route=



[:

Add a static route with route options, which are
separated by a colon. IPv6 addresses have to be put in brackets.
Example
rd.route=192.168.200.0/24:192.168.100.222:ens10
rd.route=192.168.200.0/24:192.168.100.222
rd.route=192.168.200.0/24::ens10
rd.route=[2001:DB8:3::/8]:[2001:DB8:2::1]:ens10
bootdev=

specify network interface to use routing and netroot
information from. Required if multiple ip= lines are used.
BOOTIF=

specify network interface to use routing and netroot
information from.
rd.bootif=0
Disable BOOTIF parsing, which is provided by PXE
nameserver=

nameserver=

...]
specify nameserver(s) to use
rd.peerdns=0
Disable DNS setting of DHCP parameters.
biosdevname=0
boolean, turn off biosdevname network interface
renaming
rd.neednet=1
boolean, bring up network even without netroot set
vlan=


Setup vlan device named on
. We support the four styles of vlan names: VLAN_PLUS_VID
(vlan0005), VLAN_PLUS_VID_NO_PAD (vlan5), DEV_PLUS_VID (eth0.0005),
DEV_PLUS_VID_NO_PAD (eth0.5)
bond=

[:

:[:

[:]]]
Setup bonding device on top of
. is a comma-separated list of physical
(ethernet) interfaces. is a comma-separated list on bonding
options (modinfo bonding for details) in format compatible with initscripts.
If includes multi-valued arp_ip_target option, then its values
should be separated by semicolon. if the mtu is specified, it will be set on
the bond master. Bond without parameters assumes
bond=bond0:eth0,eth1:mode=balance-rr
team=


[:

Setup team device on top of
. is a comma-separated list of physical
(ethernet) interfaces. is the runner type to be used (see
man:teamd.conf[5,external]); defaults to activebackup. Team without parameters
assumes team=team0:eth0,eth1:activebackup
bridge=


Setup bridge with .
is a comma-separated list of physical (ethernet) interfaces.
Bridge without parameters assumes bridge=br0:eth0
NFS
Requires the dracut
nfs
module.
root=
__
[:

mount nfs share from :/,
if no server-ip is given, use dhcp next_server. If server-ip is an IPv6
address it has to be put in brackets, e.g. [2001:DB8::1]. NFS options can be
appended with the prefix ":" or "," and are separated by
",".
root=
nfs:[

:]
__
[:

],
root=
nfs4:[

:]
__
[:

],
root=
{dhcp|dhcp6}
netroot=dhcp alone directs initrd to look at the DHCP
root-path where NFS options can be specified.
Example
root-path=:[,]
root-path=nfs::[,]
root-path=nfs4::[,]
root=
/dev/nfs
nfsroot=
__
[:

Deprecated!
kernel
Documentation_/filesystems/nfsroot.txt_ defines this method. This is supported
by dracut, but not recommended.
rd.nfs.domain=

Set the NFSv4 domain name. Will override the settings in
/etc/idmap.conf
rd.net.dhcp.retry=

If this option is set, dracut will try to connect via
dhcp times before failing. Default is 1.
rd.net.timeout.dhcp=

If this option is set, dhclient is called with
"--timeout ".
rd.net.timeout.iflink=

Wait until link shows up. Default is 60
seconds.
rd.net.timeout.ifup=

Wait until link has state "UP".
Default is 20 seconds.
rd.net.timeout.route=

Wait until route shows up. Default is 20
seconds.
rd.net.timeout.ipv6dad=

Wait until IPv6 DAD is finished. Default
is 50 seconds.
rd.net.timeout.ipv6auto=

Wait until IPv6 automatic addresses are
assigned. Default is 40 seconds.
rd.net.timeout.carrier=

Wait until carrier is recognized. Default
is 10 seconds.
CIFS
Requires the dracut
cifs
module.
root=
cifs://[

[:

]@]


mount cifs share from :/, if no server-ip is
given, use dhcp next_server. if server-ip is an IPv6 address it has to be put
in brackets, e.g. [2001:DB8::1]. If a username or password are not specified
as part of the root, then they must be passed on the command line through
cifsuser/cifspass.
Warning
Passwords specified on the kernel command line are visible for all
users via the file
/proc/cmdline
and via dmesg or can be sniffed on the
network, when using DHCP with DHCP root-path.
cifsuser

Set the cifs username, if not specified as part of the
root.
cifspass

Set the cifs password, if not specified as part of the
root.
Warning
Passwords specified on the kernel command line are visible for all
users via the file
/proc/cmdline
and via dmesg or can be sniffed on the
network, when using DHCP with DHCP root-path.
iSCSI
Requires the dracut
iscsi
module.
root=
iscsi:[


[:


]@][

]:[

]:[

][:[

]:[

]]:[

]:

protocol defaults to "6", LUN defaults to
"0". If the "servername" field is provided by BOOTP or
DHCP, then that field is used in conjunction with other associated fields to
contact the boot server in the Boot stage. However, if the
"servername" field is not provided, then the "targetname"
field is then used in the Discovery Service stage in conjunction with other
associated fields. See
rfc4173
Warning
Passwords specified on the kernel command line are visible for all
users via the file
/proc/cmdline
and via dmesg or can be sniffed on the
network, when using DHCP with DHCP root-path.
Example
root=iscsi:192.168.50.1::::iqn.2009-06.dracut:target0
If servername is an IPv6 address, it has to be put in
brackets:
Example
root=iscsi:[2001:DB8::1]::::iqn.2009-06.dracut:target0
root=
???
netroot=
iscsi:[


[:


]@][

]:[

]:[

][:[

]:[

]]:[

]:

...
multiple netroot options allow setting up multiple iscsi
disks:
Example
root=UUID=12424547
netroot=iscsi:192.168.50.1::::iqn.2009-06.dracut:target0
netroot=iscsi:192.168.50.1::::iqn.2009-06.dracut:target1
If servername is an IPv6 address, it has to be put in
brackets:
Example
netroot=iscsi:[2001:DB8::1]::::iqn.2009-06.dracut:target0
Warning
Passwords specified on the kernel command line are visible for all
users via the file
/proc/cmdline
and via dmesg or can be sniffed on the
network, when using DHCP with DHCP root-path. You may want to use
rd.iscsi.firmware.
root=
???
rd.iscsi.initiator=

rd.iscsi.target.name=

rd.iscsi.target.ip=

rd.iscsi.target.port=

rd.iscsi.target.group=

rd.iscsi.username=

rd.iscsi.password=

rd.iscsi.in.username=

rd.iscsi.in.password=

manually specify all iscsistart parameter (see
iscsistart --help
Warning
Passwords specified on the kernel command line are visible for all
users via the file
/proc/cmdline
and via dmesg or can be sniffed on the
network, when using DHCP with DHCP root-path. You may want to use
rd.iscsi.firmware.
root=
???
netroot=
iscsi
rd.iscsi.firmware=1
will read the iscsi parameter from the BIOS
firmware
rd.iscsi.login_retry_max=

maximum number of login retries
rd.iscsi.param=

will be passed as "--param
" to iscsistart. This parameter can be specified multiple
times.
Example
"netroot=iscsi rd.iscsi.firmware=1 rd.iscsi.param=node.session.timeo.replacement_timeout=30"
will result in
iscsistart -b --param node.session.timeo.replacement_timeout=30
rd.iscsi.ibft
rd.iscsi.ibft=1
: Turn on iBFT
autoconfiguration for the interfaces
rd.iscsi.mp
rd.iscsi.mp=1
: Configure all iBFT
interfaces, not only used for booting (multipath)
rd.iscsi.waitnet=0
: Turn off waiting for all interfaces to
be up before trying to login to the iSCSI targets.
rd.iscsi.testroute=0
: Turn off checking, if the route to
the iSCSI target IP is possible before trying to login.
rd.iscsi.transport=

Set the iSCSI transport name (see
man:iscsiadm[8,external]). iSCSI offload transports like
bnx2i
don’t need the network to be up in order to bring up iSCSI connections.
This parameter indicates that network setup can be skipped in the initramfs,
which makes booting with iSCSI offload cards faster and more reliable. This
parameter currently only has an effect for
=bnx2i
or
=qedi
FCoE
Requires the dracut
fcoe
module.
rd.fcoe=0
disable FCoE and lldpad
fcoe=

{dcb|nodcb}
{fabric|vn2vn}
Try to connect to a FCoE SAN through the NIC specified by

or

or EDD settings. The second
argument specifies if DCB should be used. The optional third argument
specifies whether fabric or VN2VN mode should be used. This parameter can be
specified multiple times.
Note
letters in the MAC-address must be lowercase!
NVMf
Requires the dracut
nvmf
module.
rd.nonvmf
Disable NVMf
rd.nvmf.nonbft
Disable connecting to targets from the NVMe Boot Firmware
Table. Without this parameter, NBFT connections will take precedence over
rd.nvmf.discover
rd.nvmf.nostatic
Disable connecting to targets that have been statically
configured when the initramfs was built. Targets specified with
rd.nvmf.discover on the kernel command line will still be tried.
rd.nvmf.hostnqn=

NVMe host NQN to use
rd.nvmf.hostid=

NVMe host id to use
rd.nvmf.discover=
{rdma|fc|tcp}

,[

],[

Discover and connect to a NVMe-over-Fabric controller
specified by

and the optionally

or

. The first argument
specifies the transport to use; currently only
rdma
fc
, or
tcp
are supported. This parameter can be specified multiple times.
Examples
rd.nvmf.discover=tcp,192.168.10.10,,4420
rd.nvmf.discover=fc,nn-0x201700a05634f5bf:pn-0x201900a05634f5bf,nn-0x200000109b579ef3:pn-0x100000109b579ef3
rd.nvmf.discover=fc,auto
This special syntax determines that Fibre Channel
autodiscovery is to be used rather than regular NVMe discovery. It takes
precedence over all other
rd.nvmf.discover=
arguments.
NBD
Requires the dracut
nbd
module.
root=
???
netroot=
nbd:


[:

[:

[:

]]]
mount nbd share from .
NOTE: If "exportname" instead of "port" is
given the standard port is used. Newer versions of nbd are only supported
with "exportname".
root=/dev/root netroot=dhcp
with
dhcp
root-path=
nbd:


[:

[:

[:

]]]
netroot=dhcp alone directs initrd to look at the DHCP
root-path where NBD options can be specified. This syntax is only usable in
cases where you are directly mounting the volume as the rootfs.
NOTE: If "exportname" instead of "port" is
given the standard port is used. Newer versions of nbd are only supported
with "exportname".
VIRTIOFS
Requires the dracut
virtiofs
module.
root=
virtiofs:

mount virtiofs share using the tag . The
tag name is arbitrary and must match the tag given in the qemu
-device
command.
rootfstype=
virtiofs
root=

mount virtiofs share using the tag . The
tag name is arbitrary and must match the tag given in the qemu
-device
command.
Both formats are supported by the
virtiofs
dracut module.
See
for more
information.
Example
root=virtiofs:host rw
DASD
Requires the dracut
dasd
module.
rd.dasd=
....
same syntax as the kernel module parameter (s390 only).
For more details on the syntax see the IBM book "Linux on IBM Z and IBM
LinuxONE - Device Drivers, Features, and Commands"
This parameter can be specified multiple times.
NOTE: This parameter is no longer handled by dracut itself but
with the exact same syntax by
ZFCP
Requires the dracut
zfcp
module.
rd.zfcp=
ID>


rd.zfcp can be specified multiple times on the kernel
command line.
NOTE: This parameter is no longer handled by dracut itself but
with the exact same syntax by
rd.zfcp=

If NPIV is enabled and the
allow_lun_scan
parameter to the zfcp module is set to
then the zfcp driver will be
initiating a scan internally and the and
parameters can be omitted.
NOTE: This parameter is no longer handled by dracut itself but
with the exact same syntax by
Example
rd.zfcp=0.0.4000,0x5005076300C213e9,0x5022000000000000
rd.zfcp=0.0.4000
rd.zfcp.conf=0
ignore zfcp.conf included in the initramfs
ZNET
Requires the dracut
znet
module.
rd.znet=



Activates a channel-attached network interface on s390
architecture. is one of: qeth, lcs, ctc.
is a comma-separated list of ccw device bus-IDs. The list consists of 3
entries with nettype qeth, and 2 for other nettype. is a
comma-separated list of = pairs, where
refers to a device sysfs attribute to which gets written.
rd.znet can be specified multiple times on the kernel command line.
rd.znet_ifname=


Assign network device name (i.e.
"bootnet") to the NIC corresponds to the subchannels. This is useful
when dracut’s default "ifname=" doesn’t work due to
device having a changing MAC address.
Example
rd.znet=qeth,0.0.0600,0.0.0601,0.0.0602,layer2=1,portname=foo
rd.znet=ctc,0.0.0600,0.0.0601,protocol=bar
OverlayFS
Requires the dracut
overlayfs
module.
rd.overlay
Enables the use of the
OverlayFS
kernel module, if
available, to provide a copy-on-write union directory for the root filesystem.
OverlayFS overlays are directories of the files that have changed on the
read-only base (lower) filesystem. The root filesystem is provided through a
special overlay type mount that merges at least two directories, designated
the lower and the upper. If an OverlayFS upper directory is not present on the
boot device, a tmpfs directory will be created at
/run/overlayfs
to provide temporary storage.
Persistent storage can be provided on vfat or msdos formatted devices by
supplying the OverlayFS upper directory within an embedded filesystem that
supports the creation of trusted.* extended attributes and provides a valid
d_type in readdir responses, such as with btrfs, ext4, f2fs, & xfs. On
non-vfat-formatted devices, a persistent OverlayFS overlay can extend the
available root filesystem storage up to the capacity of the LiveOS disk
device.
The
rd.overlay.readonly
option, which allows a persistent
overlayfs to be mounted read-only through a higher level transient overlay
directory, has been implemented through the multiple lower layers feature of
OverlayFS.
rd.overlay=
{LABEL=|UUID=|PARTUUID=|PARTLABEL=|/dev/}
Specifies the storage device for persistent overlay (for
both live images and regular OverlayFS). When a block device is specified, it
will be mounted and used for persistent overlay storage. For live images with
LABEL= specification, if the labeled partition does not exist, it will be
automatically created using available free space on the device.
Supported device specifications:
LABEL=
- Use the device with
the specified filesystem label.
UUID=
- Use the device with
the specified UUID.
PARTUUID=
- Use the device
with the specified partition UUID.
PARTLABEL=
- Use the device
with the specified partition label.
/dev/
- Use the specified
device path directly.
Examples
rd.overlay=LABEL=persist
rd.overlay=UUID=12345678-1234-1234-1234-123456789abc
rd.overlay=/dev/sdb1
Booting live images
Requires the dracut
dmsquash-live
module. Dracut offers
multiple options for live booted images:
SquashFS (read-only) base filesystem image
Note — There are 3 separate overlay types
available:
•Device-mapper snapshots (the original
offering),
•Device-mapper thin provisioning snapshots (see
rd.live.overlay.thin
, a later offering), and
•OverlayFS based overlay mounts (a more recent
offering).
Using one of these technologies, the system will provide a
writable overlay for the base, read-only SquashFS root filesystem. These
methods enable a relatively fast boot and lower RAM usage.
With the original Device-mapper snapshot overlay, users
must be
careful
to avoid writing too many blocks to the snapshot device. Once
the blocks of the snapshot overlay are exhausted, the whole root filesystem
becomes read-only leading to application failures. The snapshot overlay
device is marked
Overflow
, and a difficult recovery is required to
repair and enlarge the overlay offline.
When
rd.overlay=
is not specified for persistent overlay
storage, or the specified file is not found or writable, a Device-mapper
snapshot based non-persistent or temporary overlay is automatically created
as a sparse file in RAM of the initramfs. This file will only consume
content space as required blocks are allocated. This snapshot based overlay
defaults to an apparent size of 32 GiB in RAM, and can be adjusted with the
rd.live.overlay.size=
kernel command line option. This file is hidden
(and appears deleted) when the boot process switches out of the initramfs to
the main root filesystem but its loop device remains connected to the
Device-mapper snapshot.
Even with large Device-mapper overlay files for write space, the
available root filesystem capacity is limited by the total allocated size of
the base root filesystem, which often provide only a small number of
gigabytes of free space.
This shortage could be remedied by building the root filesystem
with more allocated free space, or the OverlayFS based overlay mount method
can be used.
When the
rd.overlay
option is specified or when
rd.overlay=
points to an appropriate directory with a sister at
/../ovlwork
, then an OverlayFS based overlay mount
is employed. Such a persistent OverlayFS overlay can extend the available
root filesystem storage up to the capacity of the LiveOS disk device.
For non-persistent OverlayFS overlays, the
/run/overlayfs
directory in the
/run
tmpfs is used for temporary storage. This
filesystem is typically sized to one half of the RAM total in the system.
The command:
mount -o remount,size= /run
will resize this virtual filesystem after booting.
The internal SquashFS structure is traditionally expected to
be:
squashfs.img | SquashFS from LiveCD .iso
!(mount)
/LiveOS
|- rootfs.img | Usually a ext4 filesystem image to mount read-only
!(mount)
/bin | Base Live root filesystem
/boot |
/dev |
... |
For OverlayFS mount overlays, the internal SquashFS structure may
be a direct compression of the root filesystem:
squashfs.img | SquashFS from LiveCD .iso
!(mount)
/bin | Base Live root filesystem
/boot |
/dev |
... |
Dracut uses one of the overlay methods of live booting by default.
No additional command line options are required other than
root=
live:

or
root=
live:

to specify the location of your squashed
root filesystem.
•The compressed SquashFS image can be copied
during boot to RAM at
/run/initramfs/squashed.img
by
using the
rd.live.ram=1
option.
•A device with a persistent overlay can be booted
read-only by using the
rd.live.overlay.readonly
option on the kernel
command line. This will either cause a temporary, writable overlay to be
stacked over a read-only snapshot of the root filesystem or the OverlayFS
mount will use an additional lower layer with the root filesystem.
Uncompressed live filesystem image
When the live system was installed with the
--skipcompress
option of the
livecd-iso-to-disk
installation
script for Live USB devices, the root filesystem image,
rootfs.img
, is
expanded on installation and no SquashFS is involved during boot.
•If
rd.live.ram=1
is used in this
situation, the full, uncompressed root filesystem is copied during boot to
/run/initramfs/rootfs.img
in the
/run
tmpfs.
•If
rd.overlay=none
is provided as a kernel
command line option, a writable, linear Device-mapper target is created on
boot with no overlay.
Writable filesystem image
The system will retrieve a compressed filesystem image,
extract it to
/run/initramfs/fsimg/rootfs.img
, connect
it to a loop device, create a writable, linear Device-mapper target at
/dev/mapper/live-rw
, and mount that as a writable
volume at
. More RAM is required during boot but the
live filesystem is easier to manage if it becomes full. Users can make a
filesystem image of any size and that size will be maintained when the system
boots. There is no persistence of root filesystem changes between boots with
this option.
The filesystem structure is expected to be:
rootfs.tgz | Compressed tarball containing filesystem image
!(unpack)
/rootfs.img | Filesystem image at /run/initramfs/fsimg/
!(mount)
/bin | Live filesystem
/boot |
/dev |
... |
To use this boot option, ensure that
rd.writable.fsimg=1
is
in your kernel command line and add the
root=live:
to
specify the location of your compressed filesystem image tarball or SquashFS
image.
rd.writable.fsimg=
Enables writable filesystem support. The system will boot
with a fully writable (but non-persistent) filesystem without snapshots
(see notes above
about available live boot options)
. You can use
the
rootflags
option to set mount options for the live filesystem as
well
(see documentation about
rootflags in the
Standard
section above)
This implies that the
whole image is copied to RAM before the boot continues.
Note
There must be enough free RAM available to hold the complete
image.
This method is very suitable for diskless boots.
rd.minmem=

Specify minimum free RAM in MB after copying a live disk
image into memory. The default is 1024.
This parameter only applies together with the parameters
rd.writable.fsimg or rd.live.ram.
root=
live:

Boots a live image retrieved from

Requires the dracut
livenet
module. Valid handlers:
http, https,
ftp, torrent, tftp
Examples
root=live:http://example.com/liveboot.img
root=live:ftp://ftp.example.com/liveboot.img
root=live:torrent://example.com/liveboot.img.torrent
root=

This is an alias for
root=
live:

Boots a live image retrieved from

. Requires the dracut
livenet
module. Valid handlers:
http, https
Examples
root=http://example.com/root.squashfs
root=https://example.com/live.sqfs
rd.live.debug=
Enables debug output from the live boot process.
rd.live.dir=

Specifies the directory within the boot device where the
squashfs.img or rootfs.img can be found. By default, this is
/LiveOS
rd.live.squashimg=
image>
Specifies the filename for a SquashFS image of the root
filesystem. By default, this is
squashfs.img
rd.live.ram=
Copy the complete image to RAM and use this for booting.
This is useful when the image resides on, e.g., a DVD which needs to be
ejected later on.
rd.overlay={

[:
{|auto}
]|
none
Manage the usage of a persistent overlay for live images.

specifies the path to a
device with a mountable filesystem.

is a path within the

filesystem to either
•a file (that is loop mounted for a Device-mapper
overlay) or
•a directory (that is symbolically linked to
/run/overlayfs
for a OverlayFS mount overlay). (A
required sister directory
//../ovlwork
is automatically made.)
none
(the word itself) specifies that no
overlay will be used, such as when an uncompressed, writable live root
filesystem is available.
The above method shall be used to persist the changes made to the
root filesystem specified within the
root=
live:

or
root=
live:

device.
The default
pathspec
, when
:auto
or no

is given, is
//overlay--
where

and

are the LABEL and UUID of
the filesystem specified by the
root=
live:

device.
If a persistent overlay
is detected
at the standard LiveOS
path, and
rd.overlay
is not set to 1, the overlay type (either
Device-mapper or OverlayFS) will be detected and it will be used.
Examples
rd.overlay=/dev/sdb1:/persistent-overlay.img
rd.overlay=UUID=99440c1f-8daa-41bf-b965-b7240a8996f4
rd.live.overlay.cowfs=
[btrfs|ext4|xfs]
Specifies the filesystem to use when formatting the
overlay partition. The default is ext4.
rd.live.overlay.size=

Specifies a non-persistent Device-mapper overlay size in
MiB. The default is
32768
rd.live.overlay.readonly=
This is used to boot in a read-only mode with a normally
read-write persistent overlay. With this option,
•Device-mapper overlays will have an additional,
non-persistent, writable snapshot overlay stacked over a read-only snapshot
/dev/mapper/live‑ro
) of the base root
filesystem and the persistent overlay, or
•for writable
rootfs.img
images, the above over a read-only loop device, or
•an OverlayFS mount will link the persistent
overlay directory at
/run/overlayfs‑r
as an
additional read-only lower layer stacked over the base root filesystem, and
/run/overlayfs
becomes the temporary, writable, upper
directory overlay, to complete the bootable root filesystem.
rd.live.overlay.nouserconfirmprompt=
Suppresses the
Using temporary overlay
blocking
prompt that asks for a user confirmation before proceeding to boot. This
allows the boot process to continue to completion without user
interation.
rd.overlay.reset=
Specifies that a persistent overlay should be reset on
boot. All previous root filesystem changes are vacated by this action.
rd.live.overlay.thin=
Enables the usage of thin snapshots instead of classic dm
snapshots. The advantage of thin snapshots is that they support discards, and
will free blocks that are not claimed by the filesystem. In this use case,
this means that memory is given back to the kernel when the filesystem does
not claim it anymore.
ZIPL
Requires the dracut
zipl
module.
rd.zipl=

Update the dracut commandline with the values found in
the
dracut-cmdline.conf
file on the given device. The values are merged
into the existing commandline values and the udev events are regenerated.
Example
rd.zipl=UUID=0fb28157-99e3-4395-adef-da3f7d44835a
CIO_IGNORE
Requires the dracut
cio_ignore
module.
rd.cio_accept=

Remove the devices listed in from the
default cio_ignore kernel command-line settings. is a list
of comma-separated CCW device ids. The default for this value is taken from
the
/boot/zipl/active_devices.txt
file.
Example
rd.cio_accept=0.0.0180,0.0.0800,0.0.0801,0.0.0802
Plymouth Boot Splash
Requires the dracut
plymouth
module.
plymouth.enable=0
disable the plymouth bootsplash completely.
rd.plymouth=0
disable the plymouth bootsplash only for the
initramfs.
Kernel keys
masterkey=

Set the path name of the kernel master key.
Example
masterkey=/etc/keys/kmk-trusted.blob
masterkeytype=

Set the type of the kernel master key.
Example
masterkeytype=trusted
evmkey=

Set the path name of the EVM HMAC key.
Example
evmkey=/etc/keys/evm-trusted.blob
evmx509=

Set the path name of the EVM X.509 certificate.
Example
evmx509=/etc/keys/x509_evm.der
ecryptfskey=

Set the path name of the eCryptfs key.
Example
ecryptfskey=/etc/keys/ecryptfs-trusted.blob
Deprecated, renamed Options
Here is a list of options and their new replacement.
rd_NO_DM
rd.dm=0 (since version 008)
rd_NO_MDADMCONF
rd.md.conf=0 (since version 008)
rd_NO_MDIMSM
rd.md.imsm=0 (since version 008)
rd_NO_MD
rd.md=0 (since version 008)
rd_MD_UUID
rd.md.uuid (since version 008)
iscsi_initiator
rd.iscsi.initiator (since version 008)
iscsi_target_name
rd.iscsi.target.name (since version 008)
iscsi_target_ip
rd.iscsi.target.ip (since version 008)
iscsi_target_port
rd.iscsi.target.port (since version 008)
iscsi_target_group
rd.iscsi.target.group (since version 008)
iscsi_username
rd.iscsi.username (since version 008)
iscsi_password
rd.iscsi.password (since version 008)
iscsi_in_username
rd.iscsi.in.username (since version 008)
iscsi_in_password
rd.iscsi.in.password (since version 008)
iscsi_firmware
rd.iscsi.firmware=0 (since version 008)
rdudevdebug
rd.udev.udev_log=debug (since version 102)
rdudevinfo
rd.udev.udev_log=info (since version 102)
rd.udev.debug
rd.udev.udev_log=debug (since version 102)
rd.udev.info
rd.udev.udev_log=info (since version 102)
KEYMAP
vconsole.keymap (since version 008)
KEYTABLE
vconsole.keymap (since version 008)
SYSFONT
vconsole.font (since version 008)
CONTRANS
vconsole.font.map (since version 008)
UNIMAP
vconsole.font.unimap (since version 008)
UNICODE
vconsole.unicode (since version 008)
EXT_KEYMAP
vconsole.keymap.ext (since version 008)
rd.live.overlay.overlayfs
rd.overlay (since version 110)
rd.live.overlay.readonly
rd.overlay.readonly (since version 110)
rd.live.overlay
rd.overlay (since version 110)
rd.live.overlay.reset
rd.overlay.reset (since version 110)
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.
AUTHOR
Harald Hoyer
SEE ALSO
man:dracut[8] man:dracut.conf[5]
2026-02-27
dracut
Package information:
Package name:
extra/dracut
Version:
110-2
Upstream:
Licenses:
GPL-2.0-or-later
Manuals:
/listing/extra/dracut/
Table of contents