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=ext3
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 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 30 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 genereted 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 on defined breakpoint
rd.udev.info
set udev to loglevel info
rd.udev.debug
set udev to loglevel debug
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
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 loosing 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.
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
ip={dhcp|on|any|dhcp6|auto6|either6|single-dhcp}
dhcp|on|any
get ip from dhcp server from all interfaces. If
root=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 and to
SUSE using wicked.
auto6
IPv6 autoconfiguration
dhcp6
IPv6 DHCP
either6
if auto6 fails, then dhcp6
ip=<interface>:{dhcp|on|any|dhcp6|auto6}[:[<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
<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}
root=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
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.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. The <traddr>
parameter can be set to auto to select autodiscovery; in that
case all other parameters are ignored. This parameter can be
specified multiple times.
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=dhcp with dhcp
root-path=nbd:<server>:<port/exportname>[:<fstype>[:<mountopts>[:<nbdopts>]]]
root=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".
DASD
rd.dasd=....
same syntax as the kernel module parameter (s390 only)
ZFCP
rd.zfcp=<zfcp adaptor device bus ID>,<WWPN>,<FCPLUN>
rd.zfcp can be specified multiple times on the kernel command
line.
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 adaptor will be
initiating a scan internally and the <WWPN> and <FCPLUN>
parameters can be omitted.
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>
The whole parameter is appended to /etc/ccw.conf, which is
used on RHEL/Fedora with ccw_init, which is called from udev
for certain devices on z-series. 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 with read-only filesystem image
The system will boot with a read-only filesystem from the
SquashFS and apply a writable Device-mapper snapshot or an
OverlayFS overlay mount for the read-only base filesystem.
This method ensures a relatively fast boot and lower RAM
usage. Users must be careful to avoid writing too many blocks
to a snapshot volume. Once the blocks of the snapshot overlay
are exhausted, the root filesystem becomes read-only and may
cause application failures. The snapshot overlay file is
marked Overflow, and a difficult recovery is required to
repair and enlarge the overlay offline. Non-persistent
overlays are sparse files in RAM that only consume content
space as required blocks are allocated. They default to an
apparent size of 32 GiB in RAM. The size can be adjusted with
the rd.live.overlay.size= kernel command line option.
The filesystem structure is traditionally expected to be:
squashfs.img | SquashFS from LiveCD .iso
!(mount)
/LiveOS
|- rootfs.img | Filesystem image to mount read-only
!(mount)
/bin | Live filesystem
/boot |
/dev |
... |
For OverlayFS mount overlays, the filesystem structure may
also be a direct compression of the root filesystem:
squashfs.img | SquashFS from LiveCD .iso
!(mount)
/bin | Live 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:<URL> to specify the location of your
squashed 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.
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 permanent overlay.
• <devspec> specifies the path to a device with a mountable
filesystem.
• <pathspec> is the path to a file within that filesystem,
which shall be used to persist the changes made to the
device specified by the root=live:<url> option.
The default pathspec, when auto or no :<pathspec> is
given, is /<rd.live.dir>/overlay-<label>-<uuid>, where
<label> is the device LABEL, and <uuid> is the device
UUID. * none (the word itself) specifies that no overlay
will be used, such as when an uncompressed, writable live
root filesystem is available.
If a persistent overlay is detected at the standard
LiveOS path, the overlay & overlay type detected, whether
Device-mapper or OverlayFS, will be used.
Examples.
rd.live.overlay=/dev/sdb1:persistent-overlay.img
rd.live.overlay=UUID=99440c1f-8daa-41bf-b965-b7240a8996f4
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 with a normally read-write persistent
overlay in a read-only mode. With this option, either an
additional, non-persistent, writable snapshot overlay will be
stacked over a read-only snapshot, /dev/mapper/live-ro, of
the base filesystem with the persistent overlay, or a
read-only loop device, in the case of a writable rootfs.img,
or an OverlayFS mount will use the persistent overlay
directory linked at /run/overlayfs-r as an additional lower
layer along with the base root filesystem and apply a
transient, writable upper directory overlay, in order to
complete the booted 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 the lower and upper directories. 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 ext4 and 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.
If a persistent overlay is detected at the standard LiveOS
path, the overlay & overlay type detected, whether OverlayFS
or Device-mapper, will be used.
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 key path name>
Set the path name of the EVM key.
Example.
evmkey=/etc/keys/evm-trusted.blob
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, which were used in dracut prior to
version 008, 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_SNAPSHOT
rd.lvm.snapshot
rd_LVM_SNAPSIZE
rd.lvm.snapsize
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.debug
rdudevinfo
rd.udev.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.
