Provided by: dracut-core_103-1ubuntu3_amd64 
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=<label_of_root> the initramfs will search all available devices for a
filesystem with the appropriate label, and mount that device as the root filesystem.
root=UUID=<uuidnumber> 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=<path to real init>
specify the path to the init program to be started after the initramfs has finished
root=<path to blockdevice>
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=<filesystem type>
"auto" if not specified.
Example.
rootfstype=ext4
rootflags=<mount options>
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=<path to blockdevice>
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=<path to resume partition>
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.
Example.
menuentry 'Live Fedora 20' --class fedora --class gnu-linux --class gnu --class os {
set isolabel=Fedora-Live-LXDE-x86_64-20-1
set isofile="/boot/iso/Fedora-Live-LXDE-x86_64-20-1.iso"
loopback loop $isofile
linux (loop)/isolinux/vmlinuz0 boot=isolinux iso-scan/filename=$isofile root=live:LABEL=$isolabel ro rd.live.image quiet rhgb
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=<drivername>[,<drivername>,...]
do not load kernel module <drivername>. This parameter can be specified multiple
times.
rd.driver.pre=<drivername>[,<drivername>,...]
force loading kernel module <drivername>. This parameter can be specified multiple
times.
rd.driver.post=<drivername>[,<drivername>,...]
force loading kernel module <drivername> after all automatic loading modules have been
loaded. This parameter can be specified multiple times.
rd.retry=<seconds>
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.
rd.timeout=<seconds>
specify how long dracut should wait for devices to appear. The default is 0, 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.
rd.ctty=<terminal device>
specify the controlling terminal for the console. This is useful, if you have multiple
"console=" arguments.
rd.shutdown.timeout.umount=<seconds>
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 0 means to wait forever. The default is 90
seconds.
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 initramsfs 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
rd.vconsole.keymap=<keymap base file name>
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=<list of keymap base file 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=<font base file name>
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=<console map base file 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=<unicode table base file 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=<locale>
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=<locale>
taken from the environment; will be written as LC_ALL to /etc/locale.conf in the
initramfs
LVM
rd.lvm=0
disable LVM detection
rd.lvm.vg=<volume group name>
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=<volume group name>/<logical volume 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
rd.luks=0
disable crypto LUKS detection
rd.luks.uuid=<luks uuid>
only activate the LUKS partitions with the given UUID. Any "luks-" of the LUKS UUID is
removed before comparing to <luks uuid>. The comparisons also matches, if <luks 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. <luks uuid> may be prefixed by the
keyword keysource:, see rd.luks.key below.
rd.luks.allow-discards=<luks uuid>
Allow using of discards (TRIM) requests for LUKS partitions with the given UUID. Any
"luks-" of the LUKS UUID is removed before comparing to <luks uuid>. The comparisons
also matches, if <luks 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.
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=<seconds>
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 0, 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 fstab(5) 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 dracut.conf(5) and
https://bugzilla.redhat.com/show_bug.cgi?id=905683 for more information.
rd.luks.key=<keypath>[:<keydev>[:<luksdev>]]
<keypath> is the pathname of a key file, relative to the root of the filesystem on
some device. It’s REQUIRED. When <keypath> 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 comes with the crypt-gpg module, which needs to be added explicitly.
<keydev> 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 <luksdev> is given, the specified key will only be used for the specified LUKS
device. Possible values are the same as for <keydev>. 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 A, B and C with the uuids aaaa, bbbb and cccc. You
want to unlock A and B 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 A, B and C is setup with a passphrase. Another luks keyslot
of each A and B 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 C and uses the keyfile to unlock A and B. If
getting the passphrase for C fails it falls back to asking for the passphrases for A
and B.
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 initialise.
MD RAID
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=<md raid uuid>
only activate the raid sets with the given UUID. This parameter can be specified
multiple times.
DM RAID
rd.dm=0
disable DM RAID detection
rd.dm.uuid=<dm raid uuid>
only activate the raid sets with the given UUID. This parameter can be specified
multiple times.
MULTIPATH
rd.multipath=0
disable multipath detection
rd.multipath=default
use default multipath settings
FIPS
rd.fips
enable FIPS
boot=<boot device>
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=<uuid>
boot=LABEL=<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: http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames
Two character prefixes based on the type of interface:
en
ethernet
wl
wlan
ww
wwan
Type of names:
o<index>
on-board device index number
s<slot>[f<function>][d<dev_id>]
hotplug slot index number
x<MAC>
MAC address
[P<domain>]p<bus>s<slot>[f<function>][d<dev_id>]
PCI geographical location
[P<domain>]p<bus>s<slot>[f<function>][u<port>][..][c<config>][i<interface>]
USB port number chain
All multi-function PCI devices will carry the [f<function>] 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 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=<interface>:{dhcp|on|any|dhcp6|auto6|link6}[:[<mtu>][:<macaddr>]]
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
<macaddr>
optionally set <macaddr> on the <interface>. This cannot be used in conjunction
with the ifname argument for the same <interface>.
ip=<client-IP>:[<peer>]:<gateway-IP>:<netmask>:<client_hostname>:<interface>:{none|off|dhcp|on|any|dhcp6|auto6|ibft}[:[<mtu>][:<macaddr>]]
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. <peer>
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.
<macaddr>
optionally set <macaddr> on the <interface>. This cannot be used in conjunction
with the ifname argument for the same <interface>.
ip=<client-IP>:[<peer>]:<gateway-IP>:<netmask>:<client_hostname>:<interface>:{none|off|dhcp|on|any|dhcp6|auto6|ibft}[:[<dns1>][:<dns2>]]
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. <peer>
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=<interface>:<MAC>
Assign network device name <interface> (i.e. "bootnet") to the NIC with MAC <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=<net>/<netmask>:<gateway>[:<interface>]
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=<interface>
specify network interface to use routing and netroot information from. Required if
multiple ip= lines are used.
BOOTIF=<MAC>
specify network interface to use routing and netroot information from.
rd.bootif=0
Disable BOOTIF parsing, which is provided by PXE
nameserver=<IP> [nameserver=<IP> ...]
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=<vlanname>:<phydevice>
Setup vlan device named <vlanname> on <phydevice>. 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=<bondname>[:<bondslaves>:[:<options>[:<mtu>]]]
Setup bonding device <bondname> on top of <bondslaves>. <bondslaves> is a
comma-separated list of physical (ethernet) interfaces. <options> is a comma-separated
list on bonding options (modinfo bonding for details) in format compatible with
initscripts. If <options> 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=<teammaster>:<teamslaves>[:<teamrunner>]
Setup team device <teammaster> on top of <teamslaves>. <teamslaves> is a
comma-separated list of physical (ethernet) interfaces. <teamrunner> is the runner
type to be used (see teamd.conf(5)); defaults to activebackup. Team without parameters
assumes team=team0:eth0,eth1:activebackup
bridge=<bridgename>:<ethnames>
Setup bridge <bridgename> with <ethnames>. <ethnames> is a comma-separated list of
physical (ethernet) interfaces. Bridge without parameters assumes bridge=br0:eth0
NFS
root=[<server-ip>:]<root-dir>[:<nfs-options>]
mount nfs share from <server-ip>:/<root-dir>, 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:[<server-ip>:]<root-dir>[:<nfs-options>],
root=nfs4:[<server-ip>:]<root-dir>[:<nfs-options>], root={dhcp|dhcp6}
netroot=dhcp alone directs initrd to look at the DHCP root-path where NFS options can
be specified.
Example.
root-path=<server-ip>:<root-dir>[,<nfs-options>]
root-path=nfs:<server-ip>:<root-dir>[,<nfs-options>]
root-path=nfs4:<server-ip>:<root-dir>[,<nfs-options>]
root=/dev/nfs nfsroot=[<server-ip>:]<root-dir>[:<nfs-options>]
Deprecated! kernel Documentation_/filesystems/nfsroot.txt_ defines this method. This
is supported by dracut, but not recommended.
rd.nfs.domain=<NFSv4 domain name>
Set the NFSv4 domain name. Will override the settings in /etc/idmap.conf.
rd.net.dhcp.retry=<cnt>
If this option is set, dracut will try to connect via dhcp <cnt> times before failing.
Default is 1.
rd.net.timeout.dhcp=<arg>
If this option is set, dhclient is called with "--timeout <arg>".
rd.net.timeout.iflink=<seconds>
Wait <seconds> until link shows up. Default is 60 seconds.
rd.net.timeout.ifup=<seconds>
Wait <seconds> until link has state "UP". Default is 20 seconds.
rd.net.timeout.route=<seconds>
Wait <seconds> until route shows up. Default is 20 seconds.
rd.net.timeout.ipv6dad=<seconds>
Wait <seconds> until IPv6 DAD is finished. Default is 50 seconds.
rd.net.timeout.ipv6auto=<seconds>
Wait <seconds> until IPv6 automatic addresses are assigned. Default is 40 seconds.
rd.net.timeout.carrier=<seconds>
Wait <seconds> until carrier is recognized. Default is 10 seconds.
CIFS
root=cifs://[<username>[:<password>]@]<server-ip>:<root-dir>
mount cifs share from <server-ip>:/<root-dir>, 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=<username>
Set the cifs username, if not specified as part of the root.
cifspass=<password>
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
root=iscsi:[<username>:<password>[:<reverse>:<password>]@][<servername>]:[<protocol>]:[<port>][:[<iscsi_iface_name>]:[<netdev_name>]]:[<LUN>]:<targetname>
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[1].
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:[<username>:<password>[:<reverse>:<password>]@][<servername>]:[<protocol>]:[<port>][:[<iscsi_iface_name>]:[<netdev_name>]]:[<LUN>]:<targetname>
...
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=<initiator> rd.iscsi.target.name=<target name>
rd.iscsi.target.ip=<target ip> rd.iscsi.target.port=<target port>
rd.iscsi.target.group=<target group> rd.iscsi.username=<username>
rd.iscsi.password=<password> rd.iscsi.in.username=<in username> rd.iscsi.in.password=<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=<num>
maximum number of login retries
rd.iscsi.param=<param>
<param> will be passed as "--param <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.
FCoE
rd.fcoe=0
disable FCoE and lldpad
fcoe=<edd|interface|MAC>:{dcb|nodcb}:{fabric|vn2vn}
Try to connect to a FCoE SAN through the NIC specified by <interface> or <MAC> 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
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=<hostNQN>
NVMe host NQN to use
rd.nvmf.hostid=<hostID>
NVMe host id to use
rd.nvmf.discover={rdma|fc|tcp},<traddr>,[<host_traddr>],[<trsvcid>]
Discover and connect to a NVMe-over-Fabric controller specified by <traddr> and the
optionally <host_traddr> or <trsvcid>. 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
root=??? netroot=nbd:<server>:<port/exportname>[:<fstype>[:<mountopts>[:<nbdopts>]]]
mount nbd share from <server>.
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:<server>:<port/exportname>[:<fstype>[:<mountopts>[:<nbdopts>]]]
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
root=virtiofs:<mount-tag>
mount virtiofs share using the tag <mount-tag>. The tag name is arbitrary and must
match the tag given in the qemu -device command.
rootfstype=virtiofs root=<mount-tag>
mount virtiofs share using the tag <mount-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
https://gitlab.com/virtio-fs/virtiofsd for more information.
Example.
root=virtiofs:host rw
DASD
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"
https://www.ibm.com/docs/en/linux-on-systems?topic=overview-device-drivers-features-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 https://github.com/ibm-s390-linux/s390-tools/tree/master/zdev/dracut/95zdev.
ZFCP
rd.zfcp=<zfcp adaptor device bus ID>,<WWPN>,<FCPLUN>
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 https://github.com/ibm-s390-linux/s390-tools/tree/master/zdev/dracut/95zdev.
rd.zfcp=<zfcp adaptor device bus ID>
If NPIV is enabled and the allow_lun_scan parameter to the zfcp module is set to Y
then the zfcp driver will be initiating a scan internally and the <WWPN> and <FCPLUN>
parameters can be omitted.
NOTE: This parameter is no longer handled by dracut itself but with the exact same
syntax by https://github.com/ibm-s390-linux/s390-tools/tree/master/zdev/dracut/95zdev.
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
rd.znet=<nettype>,<subchannels>,<options>
Activates a channel-attached network interface on s390 architecture. <nettype> is one
of: qeth, lcs, ctc. <subchannels> is a comma-separated list of ccw device bus-IDs. The
list consists of 3 entries with nettype qeth, and 2 for other nettype. <options> is a
comma-separated list of <name>=<value> pairs, where <name> refers to a device sysfs
attribute to which <value> gets written. rd.znet can be specified multiple times on
the kernel command line.
rd.znet_ifname=<ifname>:<subchannels>
Assign network device name <interface> (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
Booting live images
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.live.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.live.overlay.overlayfs option is specified or when rd.live.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=<nbytes> /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:<path to blockdevice> or
root=live:<URL> 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.live.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:<URL> to specify the location of your compressed filesystem
image tarball or SquashFS image.
rd.writable.fsimg=1
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=<megabyte>
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:<url>
Boots a live image retrieved from <url>. 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
rd.live.debug=1
Enables debug output from the live boot process.
rd.live.dir=<path>
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=<filename of SquashFS image>
Specifies the filename for a SquashFS image of the root filesystem. By default, this
is squashfs.img.
rd.live.ram=1
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.live.overlay={<devspec>[:{<pathspec>|auto}]|none}
Manage the usage of a persistent overlay.
• <devspec> specifies the path to a device with a mountable filesystem.
• <pathspec> is a path within the <devspec> 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 /<pathspec>/../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:<path to blockdevice> or root=live:<url> device.
The default pathspec, when :auto or no :<pathspec> is given, is
/<rd.live.dir>/overlay-<label>-<uuid>, where <label> and <uuid> are the LABEL and UUID
of the filesystem specified by the root=live:<path|url> device.
If a persistent overlay is detected at the standard LiveOS path, and
rd.live.overlay.overlayfs is not set to 1, the overlay type (either Device-mapper or
OverlayFS) will be detected and it will be used.
Examples.
rd.live.overlay=/dev/sdb1:/persistent-overlay.img
rd.live.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=<size_MiB>
Specifies a non-persistent Device-mapper overlay size in MiB. The default is 32768.
rd.live.overlay.readonly=1
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.reset=1
Specifies that a persistent overlay should be reset on boot. All previous root
filesystem changes are vacated by this action.
rd.live.overlay.thin=1
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.
rd.live.overlay.overlayfs=1
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.live.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.
ZIPL
rd.zipl=<path to blockdevice>
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
rd.cio_accept=<device-ids>
Remove the devices listed in <device-ids> from the default cio_ignore kernel
command-line settings. <device-ids> 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
plymouth.enable=0
disable the plymouth bootsplash completely.
rd.plymouth=0
disable the plymouth bootsplash only for the initramfs.
Kernel keys
masterkey=<kernel master key path name>
Set the path name of the kernel master key.
Example.
masterkey=/etc/keys/kmk-trusted.blob
masterkeytype=<kernel master key type>
Set the type of the kernel master key.
Example.
masterkeytype=trusted
evmkey=<EVM HMAC key path name>
Set the path name of the EVM HMAC key.
Example.
evmkey=/etc/keys/evm-trusted.blob
evmx509=<EVM X.509 cert path name>
Set the path name of the EVM X.509 certificate.
Example.
evmx509=/etc/keys/x509_evm.der
ecryptfskey=<eCryptfs key path name>
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.
rdbreak
rd.break
rd.ccw
rd.znet
rd_CCW
rd.znet
rd_DASD_MOD
rd.dasd
rd_DASD
rd.dasd
rdinitdebug rdnetdebug
rd.debug
rd_NO_DM
rd.dm=0
rd_DM_UUID
rd.dm.uuid
rdblacklist
rd.driver.blacklist
rdinsmodpost
rd.driver.post
rdloaddriver
rd.driver.pre
rd_NO_FSTAB
rd.fstab=0
rdinfo
rd.info
check
rd.live.check
rdlivedebug
rd.live.debug
live_dir
rd.live.dir
liveimg
rd.live.image
overlay
rd.live.overlay
readonly_overlay
rd.live.overlay.readonly
reset_overlay
rd.live.overlay.reset
live_ram
rd.live.ram
rd_NO_CRYPTTAB
rd.luks.crypttab=0
rd_LUKS_KEYDEV_UUID
rd.luks.keydev.uuid
rd_LUKS_KEYPATH
rd.luks.keypath
rd_NO_LUKS
rd.luks=0
rd_LUKS_UUID
rd.luks.uuid
rd_NO_LVMCONF
rd.lvm.conf
rd_LVM_LV
rd.lvm.lv
rd_NO_LVM
rd.lvm=0
rd_LVM_VG
rd.lvm.vg
rd_NO_MDADMCONF
rd.md.conf=0
rd_NO_MDIMSM
rd.md.imsm=0
rd_NO_MD
rd.md=0
rd_MD_UUID
rd.md.uuid
rd_NO_MULTIPATH: rd.multipath=0
rd_NFS_DOMAIN
rd.nfs.domain
iscsi_initiator
rd.iscsi.initiator
iscsi_target_name
rd.iscsi.target.name
iscsi_target_ip
rd.iscsi.target.ip
iscsi_target_port
rd.iscsi.target.port
iscsi_target_group
rd.iscsi.target.group
iscsi_username
rd.iscsi.username
iscsi_password
rd.iscsi.password
iscsi_in_username
rd.iscsi.in.username
iscsi_in_password
rd.iscsi.in.password
iscsi_firmware
rd.iscsi.firmware=0
rd_NO_PLYMOUTH
rd.plymouth=0
rd_retry
rd.retry
rdshell
rd.shell
rd_NO_SPLASH
rd.splash
rdudevdebug
rd.udev.udev_log=debug
rdudevinfo
rd.udev.udev_log=info
rd.udev.debug
rd.udev.udev_log=debug
rd.udev.info
rd.udev.udev_log=info
rd_NO_ZFCPCONF
rd.zfcp.conf=0
rd_ZFCP
rd.zfcp
rd_ZNET
rd.znet
KEYMAP
vconsole.keymap
KEYTABLE
vconsole.keymap
SYSFONT
vconsole.font
CONTRANS
vconsole.font.map
UNIMAP
vconsole.font.unimap
UNICODE
vconsole.unicode
EXT_KEYMAP
vconsole.keymap.ext
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
dracut(8) dracut.conf(5)
NOTES
1. rfc4173
http://tools.ietf.org/html/rfc4173#section-5