Table of Contents
- 1. User Manual
- A. Man Pages
- dracut
- dracut â create initial ramdisk images for preloading modules
- dracut.conf
- dracut.conf â configuration file(s) for dracut
- dracut.kernel
- dracut â dracut kernel command line options
To create a initramfs image, the most simple command is:
# dracut
This will generate a general purpose initramfs image, with all possible functionality resulting of the combination of the installed dracut modules and system tools. The image is /boot/initramfs-<kernel version>.img and contains the kernel modules of the currently active kernel with version <kernel version>.
If the initramfs image already exists, dracut will display an error message, and to overwrite the existing image, you have to use the --force option.
# dracut --force
If you want to specify another filename for the resulting image you would issue a command like:
# dracut foobar.img
To generate an image for a specific kernel version, the command would be:
# dracut foobar.img 2.6.40-1.rc5.f20
A shortcut to generate the image at the default location for a specific kernel version is:
# dracut '' 2.6.40-1.rc5.f20
If you want to create lighter, smaller initramfs images, you may want to specify the --host-only or -H option. Using this option, the resulting image will contain only those dracut modules, kernel modules and filesystems, which are needed to boot this specific machine. This has the drawback, that you can't put the disk on another controller or machine, and that you can't switch to another root filesystem, without recreating the initramfs image. The usage of the --host-only option is only for experts and you will have to keep the broken pieces. At least keep a copy of a general purpose image (and corresponding kernel) as a fallback to rescue your system.
To see the contents of the image created by dracut, you can use the lsinitrd tool.
# lsinitrd /boot/initramfs-$(uname -r).img | less
To display the contents of a file in the initramfs also use the lsinitrd tool:
# lsinitrd /boot/initramfs-$(uname -r).img /etc/ld.so.conf include ld.so.conf.d/*.conf
Some dracut modules are turned off by default and have to be activated manually. You can do this by adding the dracut modules to the configuration file /etc/dracut.conf or /etc/dracut.conf.d/myconf.conf. See the man page dracut.conf(5). You can also add dracut modules on the command line by using the -a or --add option:
# dracut --add bootchart initramfs-bootchart.img
To see a list of available dracut modules, issue the command:
# for mod in /usr/share/dracut/modules.d/*; do echo ${mod##*/??}; doneSometimes you don't want a dracut module to be included for reasons of speed, size or functionality. To do this, either specify the omit_dracutmodules variable in the dracut.conf or /etc/dracut.conf.d/myconf.conf configuration file (see man page dracut.conf(5)), or use the -o or --omit option on the command line:
# dracut -o "multipath lvm" no-multipath-lvm.img
If you need a special kernel module in the initramfs, which is not automatically picked up by dracut, you have the use the --add-drivers option on the command line or the drivers vaiable in the /etc/dracut.conf or /etc/dracut.conf.d/myconf.conf configuration file (see man page dracut.conf(5)):
# dracut --add-drivers mymod initramfs-with-mymod.img
dracut searches for kernel modules in
/lib/modules/<kernel version>/kernel/drivers/lib/modules/<kernel version>/updates/lib/modules/<kernel version>/extra/lib/modules/<kernel version>/weak-updates
The generated initramfs.img file normally does not contain any system configuration files (except for some special exceptions), so the configuration has to be done on the kernel command line. With this flexibility, you can easily boot from a changed root partition, without the need to recompile the initramfs image. So, you could completly change your root partition (move it inside a md raid with encryption and LVM on top), as long as you specify the correct filesystem LABEL or UUID on the kernel command line for your root device, dracut will find it and boot from it.
The kernel command line usually can be configured in /boot/grub/grub.conf, if grub is your bootloader and it also can be edited in the real boot process in the grub menu.
The kernel command line can also be provided by the dhcp server with the root-path option. See the section called âNetwork Bootâ.
For a full reference of all kernel command line parameters, see the dracut.conf(5) or dracut(8) man page.
This is the only option dracut really needs to boot from your root partition. Because your root partition can live in various environments, there are a lot of formats for the root= option. The most basic one is root=:<path to device node>
root=/dev/sda2
Because device node names can change, dependent on the drive ordering, you are encouraged to use the filesystem identifier (UUID) or filesystem label (LABEL) to specify your root partition:
root=UUID=19e9dda3-5a38-484d-a9b0-fa6b067d0331
or
root=LABEL=myrootpartitionlabel
To see all UUIDs or LABELs on your system, do:
# ls -l /dev/disk/by-uuid
or
# ls -l /dev/disk/by-label
If your root partition is on the network see the section called âNetwork Bootâ.
If you have to input passwords for encrypted disk volumes, you might want to set the keyboard layout and specify a display font.
A typical german kernel command would contain:
LANG=de_DE.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=de-latin1-nodeadkeys
dracut can force load a kernel module with the rdloaddriver= kernel command line parameter, if the kernel module is included in the initramfs (see previous section). If you want the kernel module to be force loaded after all automatic loading modules have been loaded, use the <drivername>rdrdinsmodpost= kernel command line parameter.<drivername>
Sometimes it is required to prevent the automatic kernel module loading of a specific kernel module. To do this, just add rd.blacklist=, with <kernel module name><kernel module name> not containing the .ko suffix, to the kernel command line. For example:
rdblacklist=mptsas rdblacklist=nouveau
The option can be specified multiple times on the kernel command line.
If you want to speed up the boot process, you can specify as much information for dracut on the kernel command as possible. For example, you can tell dracut, that you root partition is not on a LVM volume or not on a raid partition, or that it lives inside a specific crypto LUKS encrypted volume. By default, dracut searches everywhere. A typical dracut kernel command line for a plain primary or logical partition would contain:
rd_NO_LUKS rd_NO_LVM rd_NO_MD rd_NO_DM
This turns off every automatic assembly of LVM, MD raids, DM raids and crypto LUKS.
Of course, you could also omit the dracut modules in the initramfs creation process, but then you would lose the posibility to turn it on on demand.
To add your own files to the initramfs image, you have several possibilities.
The --include option let you specify a source path and a target path. For example
# dracut --include cmdline-preset /etc/cmdline initramfs-cmdline-pre.img
will create an initramfs image, where the file cmdline-preset will be copied inside the initramfs to /etc/cmdline. --include can only be specified once.
# mkdir overlay
# mkdir overlay/etc
# mkdir overlay/etc/conf.d
# echo "ip=auto" >> overlay/etc/cmdline
# echo export TESTVAR=testtest >> overlay/etc/conf.d/testvar.conf
# echo export TESTVAR=testtest >> overlay/etc/conf.d/testvar.conf
# tree overlay/
overlay/
âââ etc
âââ cmdline
âââ conf.d
âââ testvar.conf
# dracut --include overlay / initramfs-overlay.imgThis will put the contents of the overlay directory into the root of the initramfs image.
The --install option let you specify several files, which will get installed in the initramfs image at the same location, as they are present on initramfs creation time.
# dracut --install 'strace fsck.ext3 ssh' initramfs-dbg.img
This will create an initramfs with the strace, fsck.ext3 and ssh executables, together with the libraries needed to start those. The --install option can be specified multiple times.
If your root partition is on a network drive, you have to have the network dracut modules installed to create a network aware initramfs image.
On a Red Hat Enterprise Linux or Fedora system, this means, you have to install the dracut-network rpm package:
# yum install dracut-network
The resulting initramfs image can be served by a boot manager residing on your local hard drive or it can be served by a PXE/TFTP server.
How to setup your PXE/TFTP server can be found in the Red Hat Enterprise Linux Storage Administration Guide.
If you specify rd.ip=auto on the kernel command line, then dracut asks a dhcp server about the ip adress for the machine. The dhcp server can also serve an additional root-path, which will set the root device for dracut. With this mechanism, you have static configuration on your client machine and a centralized boot configuration on your TFTP/DHCP server. If you can't pass a kernel command line, then you can inject /etc/cmdline, with a method described in the section called âInjecting custom Filesâ.
To reduce the size of the initramfs, you should create it with by ommitting all dracut modules, which you know, you don't need to boot the machine.
You can also specify the exact dracut and kernel modules to produce a very tiny initramfs image.
For example for a NFS image, you would do:
# dracut -m "nfs network base" initramfs-nfs-only.img
Then you would boot from this image with your target machine and reduce the size once more by creating it on the target machine with the --host-only option:
# dracut -m "nfs network base" --host-only initramfs-nfs-host-only.img
This will reduce the size of the initramfs image significantly.
If the boot process does not succeed, you have several options to debug the situation. Some of the basic operations are covered here. For more information you should also visit: http://fedoraproject.org/wiki/How_to_debug_Dracut_problems
Remove ''rhgb'' and ''quiet'' from the kernel command line
Add ''rdshell'' to the kernel command line. This will present a shell should dracut be unable to locate your root device
Add ''rdshell rdinitdebug'' to the kernel command line so that dracut shell commands are printed as they are executed
With dracut >= 002-11, you can inspect the rdinitdebug output with:
# less /init.log # dmesg | less
In all cases, the following should be mentioned and attached to your bug report:
The exact kernel command-line used. Typically from the bootloader configuration file (e.g.
/etc/grub.conf) or from/proc/cmdline.A copy of your disk partition information from
/etc/fstab, which might be obtained booting an old working initramfs or a rescue medium.A device listing from device-mapper. This can be obtained by running the command
# dmsetup ls --tree
A list of block device attributes including vol_id compatible mode. This can be obtained by running the commands:
# blkid -p # blkid -p -o udevTurn on dracut debugging (see
the 'debugging dracut' section), and attach all relevant information from the boot log. This can be obtained by running the command# dmesg|grep dracut
If you use a dracut configuration file, please include
/etc/dracut.confand all files in/etc/dracut.conf.d/*.conf
As well as the information from the section called âAll bug reportsâ include the following information:
Include physical volume information by running the command:
# lvm pvdisplay
Include volume group information by running the command:
# lvm vgdisplay
Include logical volume information by running the command:
# lvm lvdisplay
As well as the information from the section called âAll bug reportsâ, include the following information:
If using software RAID disk partitions, please include the output of
# cat /proc/mdstat
This section details information to include when experiencing problems on a system whose root device is located on a network attached volume (e.g. iSCSI, NFS or NBD). As well as the information from the section called âAll bug reportsâ, include the following information:
Please include the output of
# /sbin/ifup
<interfacename># ip addr show
Successfully debugging dracut will require some form of console logging during the system boot. This section documents configuring a serial console connection to record boot messages.
First, enable serial console output for both the kernel and the bootloader.
Open the file
/etc/grub.conffor editing. Below the line ''timeout=5'', add the following:serial --unit=0 --speed=9600 terminal --timeout=5 serial consoleAlso in
/etc/grub.conf, add the following boot arguemnts to the ''kernel'' line:console=tty0 console=ttyS0,9600
When finished, the
/etc/grub.conffile should look similar to the example below.default=0 timeout=5 serial --unit=0 --speed=9600 terminal --timeout=5 serial console title Fedora (2.6.29.5-191.fc11.x86_64) root (hd0,0) kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 console=ttyS0,9600 initrd /dracut-2.6.29.5-191.fc11.x86_64.imgMore detailed information on how to configure the kernel for console output can be found at http://www.faqs.org/docs/Linux-HOWTO/Remote-Serial-Console-HOWTO.html#CONFIGURE-KERNEL.
Redirecting non-interactive output
You can redirect all non-interactive output to /dev/kmsg and the kernel will put it out on the console when it reaches the kernel buffer by doing
# exec >/dev/kmsg 2>&1 </dev/console
Dracut offers a shell for interactive debugging in the event dracut fails to locate your root filesystem. To enable the shell:
Add the boot parameter ''rdshell'' to your bootloader configuration file (e.g.
/etc/grub.conf)Remove the boot arguments ''rhgb'' and ''quiet''
A sample
/etc/grub.confbootloader configuration file is listed below.default=0 timeout=5 serial --unit=0 --speed=9600 terminal --timeout=5 serial console title Fedora (2.6.29.5-191.fc11.x86_64) root (hd0,0) kernel /vmlinuz-2.6.29.5-191.fc11.x86_64 ro root=/dev/mapper/vg_uc1-lv_root console=tty0 rdshell initrd /dracut-2.6.29.5-191.fc11.x86_64.imgIf system boot fails, you will be dropped into a shell as seen in the example below.
No root device found Dropping to debug shell. sh: can't access tty; job control turned off #Use this shell prompt to gather the information requested above (see the section called âAll bug reportsâ).
From the dracut debug shell, you can manually perform the task of locating and preparing your root volume for boot. The required steps will depend on how your root volume is configured. Common scenarios include:
A block device (e.g.
/dev/sda7)A LVM logical volume (e.g.
/dev/VolGroup00/LogVol00)An encrypted device (e.g.
/dev/mapper/luks-4d5972ea-901c-4584-bd75-1da802417d83)A network attached device (e.g. netroot=iscsi:@192.168.0.4::3260::iqn.2009-02.org.fedoraproject:for.all)
The exact method for locating and preparing will vary. However, to continue with a successful boot, the objective is to locate your root volume and create a symlink /dev/root which points to the file system. For example, the following example demonstrates accessing and booting a root volume that is an encrypted LVM Logical volume.
Inspect your partitions using parted
# parted /dev/sda -s p Model: ATA HTS541060G9AT00 (scsi) Disk /dev/sda: 60.0GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 32.3kB 10.8GB 107MB primary ext4 boot 2 10.8GB 55.6GB 44.7GB logical lvmYou recall that your root volume was a LVM logical volume. Scan and activate any logical volumes.
# lvm vgscan # lvm vgchange -ayYou should see any logical volumes now using the command blkid:
# blkid /dev/sda1: UUID="3de247f3-5de4-4a44-afc5-1fe179750cf7" TYPE="ext4" /dev/sda2: UUID="Ek4dQw-cOtq-5MJu-OGRF-xz5k-O2l8-wdDj0I" TYPE="LVM2_member" /dev/mapper/linux-root: UUID="def0269e-424b-4752-acf3-1077bf96ad2c" TYPE="crypto_LUKS" /dev/mapper/linux-home: UUID="c69127c1-f153-4ea2-b58e-4cbfa9257c5e" TYPE="ext3" /dev/mapper/linux-swap: UUID="47b4d329-975c-4c08-b218-f9c9bf3635f1" TYPE="swap"From the output above, you recall that your root volume exists on an encrypted block device. Following the guidance disk encryption guidance from the Installation Guide, you unlock your encrypted root volume.
# UUID=$(cryptsetup luksUUID /dev/mapper/linux-root) # cryptsetup luksOpen /dev/mapper/linux-root luks-$UUID Enter passphrase for /dev/mapper/linux-root: Key slot 0 unlocked.Next, make a symbolic link to the unlocked root volume
# ln -s /dev/mapper/luks-$UUID /dev/root
With the root volume available, you may continue booting the system by exiting the dracut shell
# exit
For more debugging options, see the section called âDebugâ in the man page dracut(8).
Table of Contents
- dracut
- dracut â create initial ramdisk images for preloading modules
- dracut.conf
- dracut.conf â configuration file(s) for dracut
- dracut.kernel
- dracut â dracut kernel command line options
Name
dracut â create initial ramdisk images for preloading modules
Synopsis
dracut [
OPTION
...] [
<image>
[
<kernel-version>
]
]
Description
dracut creates an initial image used by the kernel for preloading the block device modules (such as IDE, SCSI or RAID) which are needed to access the root filesystem.
For a complete list of kernel command line options see dracut.kernel(7)
Options
-
-f,--force overwrite existing initramfs file.
-
-m,--modulesÂ<list of dracut modules> specify a space-separated list of dracut modules to call when building the initramfs. Modules are located in
/usr/share/dracut/modules.d. This parameter can be specified multiple times.-
-o,--omitÂ<list of dracut modules> omit a space-separated list of dracut modules. This parameter can be specified multiple times.
-
-a,--addÂ<list of dracut modules> add a space-separated list of dracut modules to the default set of modules. This parameter can be specified multiple times.
-
-d,--driversÂ<list of kernel modules> specify a space-separated list of kernel modules to exclusively include in the initramfs. The kernel modules have to be specified without the ".ko" suffix. This parameter can be specified multiple times.
-
--add-driversÂ<list of kernel modules> specify a space-separated list of kernel modules to add to the initramfs. The kernel modules have to be specified without the ".ko" suffix. This parameter can be specified multiple times.
-
--filesystemsÂ<list of filesystems> specify a space-separated list of kernel filesystem modules to exclusively include in the generic initramfs. This parameter can be specified multiple times.
-
-k,--kmoddirÂ<kernel directory> specify the directory, where to look for kernel modules
-
--fwdirÂ<dir>[:<dir>...] specify additional directories, where to look for firmwares. This parameter can be specified multiple times.
-
--kernel-only only install kernel drivers and firmware files
-
--no-kernel do not install kernel drivers and firmware files
-
--mdadmconf include local
/etc/mdadm.conf-
--nomdadmconf do not include local
/etc/mdadm.conf-
--strip strip binaries in the initramfs (default)
-
--nostrip do not strip binaries in the initramfs
-
-h,--help display help text and exit.
-
--debug output debug information of the build process
-
-v,--verbose verbose output during the build process
-
-c,--confÂ<dracut configuration file> specify configuration file to use. Default:
/etc/dracut.conf-
--confdirÂ<configuration directory> specify configuration directory to use. Default:
/etc/dracut.conf.d-
-l,--local activates the local mode. dracut will use modules from the current working directory instead of the system-wide installed modules in
/usr/share/dracut/modules.d. This is useful when running dracut from a git checkout.-
-H,--hostonly Host-Only mode: Install only what is needed for booting the local host instead of a generic host.
Warning
If chrooted to another root other than the real root device, use "--fstab" and provide a valid
/etc/fstab.-
--fstab Use
/etc/fstabinstead of/proc/self/mountinfo.-
-i,--includeÂ<source directory>Â<target directory> include the files in the source directory into the target directory in the final initramfs.
-
-I,--installÂ<file list> install the space separated list of files into the initramfs.
Files
-
/var/log/dracut.log logfile of initramfs image creation
-
/tmp/dracut.log logfile of initramfs image creation, if
/var/log/dracut.logis not writable-
/etc/dracut.conf see dracut.conf(5)
-
/etc/dracut.conf.d/*.conf see dracut.conf(5)
Availability
The dracut command is part of the dracut package and is available from http://sourceforge.net/apps/trac/dracut/wiki
Name
dracut.conf â configuration file(s) for dracut
Synopsis
/etc/dracut.conf
/etc/dracut.conf.d/*.conf
Description
dracut.conf
is loaded during the initialisation phase of dracut.
Command line parameter will overwrite any values set here.
dracut.conf.d/*.conf files are read in alphanumerical order and will
overwrite parameters set in /etc/dracut.conf. Each line specifies an attribute and a value. A '#' indicates the beginning of a comment; following characters, up to the end of the line are not interpreted.
-
dracutmodules+="Â<dracut modules>Â " Specify a space-separated list of dracut modules to call when building the initramfs. Modules are located in
/usr/share/dracut/modules.d.-
omit_dracutmodules+="Â<dracut modules>Â " Omit a space-separated list of dracut modules.
-
add_dracutmodules+="Â<dracut modules>Â " Add a space-separated list of dracut modules.
-
drivers+="Â<kernel modules>Â " Specify a space-separated list of kernel modules to exclusively include in the initramfs. The kernel modules have to be specified without the ".ko" suffix.
-
add_drivers+="Â<kernel modules>Â " Specify a space-separated list of kernel modules to add to the initramfs. The kernel modules have to be specified without the ".ko" suffix.
-
filesystems+="Â<filesystem names>Â " Specify a space-separated list of kernel filesystem modules to exclusively include in the generic initramfs.
-
drivers_dir="<kernel modules directory>" Specify the directory, where to look for kernel modules
-
fw_dir+="Â :<dir>[:<dir>Â ...]Â " Specify additional directories, where to look for firmwares, separated by
:-
do_strip="{yes|no}" Strip binaries in the initramfs (default=yes)
-
hostonly="{yes|no}" Host-Only mode: Install only what is needed for booting the local host instead of a generic host.
Warning
If chrooted to another root other than the real root device, use
--fstaband provide a valid/etc/fstab.-
use_fstab="{yes|no}" Use
/etc/fstabinstead of/proc/self/mountinfo.-
mdadmconf="{yes|no}" Include local
/etc/mdadm.conf(default=yes)-
lvmconf="{yes|no}" Include local
/etc/lvm/lvm.conf(default=yes)-
kernel_only="{yes|no}" Only install kernel drivers and firmware files. (default=no)
-
no_kernel="{yes|no}" Do not install kernel drivers and firmware files (default=no)
Name
dracut.kernel â dracut kernel command line options
Description
The root filesystem used by the kernel is specified in the boot configuration file, as always. The traditional root=/dev/hda1 style device specification is allowed. If a label is used, as in root=LABEL=rootPart the initramfs will search all available devices for an ext2 or ext3 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.
Standard
-
init=<path to real init> -
root=<path to blockdevice> specify blockdevice to use as root filesystem. e.g.:
root=/dev/sda1 root=/dev/disk/by-path/pci-0000:00:1f.1-scsi-0:0:1:0-part1-
rootfstype=<filesystem type> "auto" if not specified, e.g.:
rootfstype=ext3
-
rootflags=<mount options> specify additional mount options for the root filesystem. If not set,
/etc/fstabof the real root will be parsed for special mount options and mounted accordingly.
Misc
-
rdblacklist=<drivername>[,<drivername>,...] do not load kernel module <drivername> This parameter can be specified multiple times.
-
rdloaddriver=<drivername>[,<drivername>,...] force loading kernel module <drivername> This parameter can be specified multiple times.
-
rdrdinsmodpost=<drivername>[,<drivername>,...] force loading kernel module <drivername> after all automatic loading modules have been loaded. This parameter can be specified multiple times.
Debug
-
rdinfo print informational output though "quiet" is set
-
rdshell allow dropping to a shell, if root mounting fails
-
rdinitdebug set -x for the dracut shell and logs to dmesg, console and
/init.log-
rdbreak drop to a shell at the end
-
rdbreak={cmdline|pre-udev|pre-trigger|initqueue|pre-mount|mount|pre-pivot} drop to a shell on defined breakpoint
-
rdudevinfo set udev to loglevel info
-
rdudevdebug set udev to loglevel debug
I18N
e.g.
LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYTABLE=de-latin1-nodeadkeys
-
KEYBOARDTYPE=sun|pc will be written to /etc/sysconfig/keyboard in the initramfs
-
KEYTABLE=<keytable filename> will be written to /etc/sysconfig/keyboard in the initramfs
-
SYSFONT=<console font> will be written to /etc/sysconfig/i18n in the initramfs
-
SYSFONTACM=<console font map> will be written to /etc/sysconfig/i18n in the initramfs
-
UNIMAP=<unicode font map> will be written to /etc/sysconfig/i18n in the initramfs
-
LANG=<locale> will be written to /etc/sysconfig/i18n in the initramfs
LVM
-
rd_NO_LVM disable LVM detection
-
rd_NO_LVM.vg=<volume group name> only activate the volume groups with the given name
rd_NO_LVM.vgcan be specified multiple times on the kernel command line.-
rd_LVM_LV=<logical volume name> only activate the logical volumes with the given name
rd_LVM_LVcan be specified multiple times on the kernel command line.-
rd_NO_LVMCONF remove any
/etc/lvm/lvm.conf, which may exist in the initramfs
crypto LUKS
-
rd_NO_LUKS 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.-
rd_NO_CRYPTTAB do not check, if LUKS partition is in
/etc/crypttab
MD
-
rd_NO_MD disable MD RAID detection
-
rd_NO_MDIMSM disable MD RAID for imsm/isw raids, use DM RAID instead
-
rd_NO_MDADMCONF ignore mdadm.conf included in initramfs
-
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_NO_DM=0disable 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.
Network
-
ip={dhcp|on|any|dhcp6|auto6} 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.
auto6: IPv6 autoconfigurationdhcp6: IPv6 DHCPip=<interface>:{dhcp|on|any|dhcp6|auto6}dhcp|on|any|dhcp6: get ip from dhcp server on a specific interface auto6: do IPv6 autoconfiguration This parameter can be specified multiple times.
ip=<client-IP>:[<server-id>]:<gateway-IP>:<netmask>:<client_hostname>:<interface>:{none|off}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.
ifname=<interface>:<MAC>Assign network device name <interface> (ie eth0) to the NIC with MAC <MAC>. Note: If you use this option you must specify an ifname= argument for all interfaces used in ip= or fcoe= arguments. This parameter can be specified multiple times.
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bootdev=<interface> specify network interface to use routing and netroot information from. Required if multiple ip= lines are used.
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nameserver=<IP>[nameserver=<IP>...] specify nameserver(s) to use
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biosdevname={0|1} turn on/off biosdevname network interface renaming
NFS
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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 seperated 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. 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>]
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root=/dev/nfsnfsroot=[<server-ip>:]<root-dir>[:<nfs-options>] Deprecated! kernel Documentation
/filesystems/nfsroot.txtdefines this method. This is supported by dracut, but not recommended.-
rd_NFS_DOMAIN=<NFSv4 domain name> Set the NFSv4 domain name. Will overwrite the settings in
/etc/idmap.conf.
iSCSI
root=iscsi:[<username>:<password>[:<reverse>:<password>]@][<servername>]:[<protocol>]:[<port>]:[<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 http://tools.ietf.org/html/rfc4173.
e.g.:
root=iscsi:192.168.50.1::::iqn.2009-06.dracut:target0
If servername is an IPv6 address, it has to be put in brackets. e.g.:
root=iscsi:[2001:DB8::1]::::iqn.2009-06.dracut:target0
root=???netroot=iscsi:[<username>:<password>[:<reverse>:<password>]@][<servername>]:[<protocol>]:[<port>]:[<LUN>]:<targetname>...multiple netroot options allow setting up multiple iscsi disks. e.g.:
root=UUID=12424547 netroot=iscsi:192.168.50.1::::iqn.2009-06.dracut:target0 netroot=iscsi:192.168.50.1::::iqn.2009-06.dracut:target1If servername is an IPv6 address, it has to be put in brackets. e.g.:
netroot=iscsi:[2001:DB8::1]::::iqn.2009-06.dracut:target0
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root=???iscsi_initiator=<initiator>iscsi_target_name=<target name>iscsi_target_ip=<target ip>iscsi_target_port=<target port>iscsi_target_group=<target group>iscsi_username=<username>iscsi_password=<password>iscsi_in_username=<in username>iscsi_in_password=<in password> manually specify all iscsistart parameter (see
iscsistart --help)-
root=???netroot=iscsiiscsi_firmware will read the iscsi parameter from the BIOS firmware
FCoE
netroot=fcoe:<interface|MAC>:{dcb|nodcb}Try to connect to a FCoE SAN through the NIC specified by
<interface>or<MAC>, for the second argument, currently only nodcb is supported. Note: letters in the MAC-address must be lowercase!
NBD
root=nbd:<server>:<port>[:<fstype>][:<mountopts>]mount nbd share from <server>
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root=dhcp with dhcp root-path=nbd:<server>:<port>[:<fstype>][:<mountopts>] 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.
DASD
rd_DASD_MOD=....same syntax as the kernel module parameter (s390 only)
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rd_DASD=<dasd_adaptor device bus ID>[,readonly=X] [,use_diag=X] [,erplog=X] activate DASD device with the given adaptor device bus ID and setting the sysfs attributes to the specified values This parameter can be specified multiple times.
ZFCP
rd_ZFCP=<zfcp adaptor device bus ID>,<WWPN>,<FCPLUN>rd_ZFCP can be specified multiple times on the kernel command line. e.g.:
rd_ZFCP=0.0.4000,0x5005076300C213e9,0x5022000000000000
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rd_NO_ZFCPCONF ignore zfcp.conf included in the initramfs