DRACUT\&.CMDLINE

Section: dracut (7)
Updated: 02/23/2021
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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=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 m[blue]https://bugzilla.redhat.com/show_bug.cgi?id=905683m[] 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 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: m[blue]http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNamesm[]

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 m[blue]rfc4173m[][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.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.
 

AUTHOR

Harald Hoyer  

SEE ALSO

dracut(8) dracut.conf(5)  

NOTES

1.
rfc4173
http://tools.ietf.org/html/rfc4173#section-5

 

Index

NAME
DESCRIPTION
Standard
iso-scan/filename
Misc
Debug
I18N
LVM
crypto LUKS
crypto LUKS - key on removable device support
MD RAID
DM RAID
MULTIPATH
FIPS
Network
NFS
CIFS
iSCSI
FCoE
NVMf
NBD
DASD
ZFCP
ZNET
Booting live images
ZIPL
CIO_IGNORE
Plymouth Boot Splash
Kernel keys
Deprecated, renamed Options
Configuration in the Initramfs
AUTHOR
SEE ALSO
NOTES