dracut.usage.asc - pub/scm/boot/dracut/dracut - Git at Google

 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 --kver 2.6.40-1.rc5.f20
 ----

 If you want to create lighter, smaller initramfs images, you may want to specify
 the --hostonly 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
 --hostonly 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.

 === Inspecting the Contents
 To see the contents of the image created by dracut, you can use the lsinitrd
 tool.
 ----
 # lsinitrd | less
 ----

 To display the contents of a file in the initramfs also use the lsinitrd tool:
 ----
 # lsinitrd -f /etc/ld.so.conf
 include ld.so.conf.d/*.conf
 ----

 === Adding dracut Modules
 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 *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, use the --list-modules option:
 ----
 # dracut --list-modules
 ----

 === Omitting dracut Modules
 Sometimes 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 *dracut.conf*(5)), or use the -o or --omit option
 on the command line:
 ----
 # dracut -o "multipath lvm" no-multipath-lvm.img
 ----

 === Adding Kernel Modules
 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 *dracut.conf*(5)):
 ----
 # dracut --add-drivers mymod initramfs-with-mymod.img
 ----

 === Boot parameters
 An initramfs generated without the "hostonly" mode, 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_ or
 _/boot/grub2/grub.cfg_, 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 <<NetworkBoot>>.

 For a full reference of all kernel command line parameters,
 see *dracut.cmdline*(5).

 To get a quick start for the suitable kernel command line on your system,
 use the __--print-cmdline__ option:
 ----
 # dracut --print-cmdline
  root=UUID=8b8b6f91-95c7-4da2-831b-171e12179081 rootflags=rw,relatime,discard,data=ordered rootfstype=ext4
 ----

 ==== Specifying the root Device
 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 <<NetworkBoot>>.

 ==== Keyboard Settings
 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:
 ----
 rd.vconsole.font=latarcyrheb-sun16 rd.vconsole.keymap=de-latin1-nodeadkeys rd.locale.LANG=de_DE.UTF-8
 ----

 Setting these options can override the setting stored on your system, if you use
 a modern init system, like systemd.

 ==== Blacklisting Kernel Modules
 Sometimes it is required to prevent the automatic kernel module loading of a
 specific kernel module. To do this, just add rd.blacklist=_++<kernel module
 name>++_, with _++<kernel module name>++_ not containing the _.ko_
 suffix, to the kernel command line. For example:
 ----
 rd.driver.blacklist=mptsas rd.driver.blacklist=nouveau
 ----

 The option can be specified multiple times on the kernel command line.

 ==== Speeding up the Boot Process
 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.luks=0 rd.lvm=0 rd.md=0 rd.dm=0
 ----

 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.


 [[Injecting]]
 === Injecting custom Files
 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.d/mycmdline.conf initramfs-cmdline-pre.img
 ----
 will create an initramfs image, where the file cmdline-preset will be copied
 inside the initramfs to _/etc/cmdline.d/mycmdline.conf_. --include can only
 be specified once.


 ----
 # mkdir -p rd.live.overlay/etc/cmdline.d
 # mkdir -p rd.live.overlay/etc/conf.d
 # echo "ip=dhcp" >> rd.live.overlay/etc/cmdline.d/mycmdline.conf
 # echo export FOO=testtest >> rd.live.overlay/etc/conf.d/testvar.conf
 # echo export BAR=testtest >> rd.live.overlay/etc/conf.d/testvar.conf
 # tree rd.live.overlay/
 rd.live.overlay/
 `-- etc
     |-- cmdline.d
     |   `-- mycmdline.conf
     `-- conf.d
         `-- testvar.conf

 # dracut --include rd.live.overlay / initramfs-rd.live.overlay.img
 ----

 This will put the contents of the rd.live.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.


 [[NetworkBoot]]
 === Network Boot

 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.

 If you specify ip=dhcp 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.d/mycmdline.conf_, with a
 method described in <<Injecting>>.

 ==== Reducing the Image Size

 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.


 == Troubleshooting

 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:
 https://www.kernel.org/pub/linux/utils/boot/dracut/dracut.html


 [[identifying-your-problem-area]]
 === Identifying your problem area
 . Remove ''rhgb'' and ''quiet'' from the kernel command line
 . Add ''rd.shell'' to the kernel command line. This will present a shell should
 dracut be unable to locate your root device
 . Add ''rd.shell rd.debug log_buf_len=1M'' to the kernel command line so that
 dracut shell commands are printed as they are executed
 . The file /run/initramfs/rdsosreport.txt is generated,
 which contains all the logs and the output of all significant tools, which are
 mentioned later.

 If you want to save that output, simply mount /boot by hand or insert an USB
 stick and mount that. Then you can store the output for later inspection.

 [[information-to-include-in-your-report]]
 === Information to include in your report

 [[all-bug-reports]]
 ==== All bug reports
 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.
 * Turn on dracut debugging (see _the 'debugging dracut' section_), and attach
 the file /run/initramfs/rdsosreport.txt.
 * If you use a dracut configuration file, please include _/etc/dracut.conf_ and
 all files in _/etc/dracut.conf.d/*.conf_

 [[network-root-device-related-problems]]
 ==== Network root device related problems
 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 <<all-bug-reports>>, include the
 following information:


 * Please include the output of
 +
 ----
 # /sbin/ifup <interfacename>
 # ip addr show
 ----

 [[debugging-dracut]]
 === Debugging dracut


 [[configure-a-serial-console]]
 ==== Configure a serial console

 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.conf_ for editing. Below the line ''timeout=5'', add
 the following:
 +
 ----
 serial --unit=0 --speed=9600
 terminal --timeout=5 serial console
 ----
 +
 . Also in _/etc/grub.conf_, add the following boot arguemnts to the ''kernel''
 line:
 +
 ----
 console=tty0 console=ttyS0,9600
 ----
 +
 . When finished, the _/etc/grub.conf_ file 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.img
 ----
 +
 . More 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
 +
 --
 NOTE: 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
 ----
 --

 [[using-the-dracut-shell]]
 ==== Using the dracut shell

 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 ''rd.shell'' to your bootloader configuration file
 (e.g. _/etc/grub.conf_)
 . Remove the boot arguments ''rhgb'' and ''quiet''
 +
 A sample _/etc/grub.conf_ bootloader 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 rd.shell
   initrd /dracut-2.6.29.5-191.fc11.x86_64.img
 ----
 +
 . If system boot fails, you will be dropped into a shell as seen in the example
 below.
 +
 ----
 No root device found
 Dropping to debug shell.

 #
 ----
 +
 . Use this shell prompt to gather the information requested above
 (see <<all-bug-reports>>).

 [[accessing-the-root-volume-from-the-dracut-shell]]
 ==== Accessing the root volume from the dracut shell
 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.example: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                lvm
 ----
 +
 . You recall that your root volume was a LVM logical volume. Scan and activate
 any logical volumes.
 +
 ----
 # lvm vgscan
 # lvm vgchange -ay
 ----
 +
 . You 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
 ----

 [[additional-dracut-boot-parameters]]
 ==== Additional dracut boot parameters
 For more debugging options, see *dracut.cmdline*(7).


 [[debugging-dracut-on-shutdown]]
 ==== Debugging dracut on shutdown

 To debug the shutdown sequence on systemd systems, you can _rd.break_
 on _pre-shutdown_ or _shutdown_.

 To do this from an already booted system:
 ----
 # mkdir -p /run/initramfs/etc/cmdline.d
 # echo "rd.debug rd.break=pre-shutdown rd.break=shutdown" > /run/initramfs/etc/cmdline.d/debug.conf
 # touch /run/initramfs/.need_shutdown
 ----

 This will give you a dracut shell after the system pivot'ed back in the
 initramfs.
	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 --kver 2.6.40-1.rc5.f20
	----

	If you want to create lighter, smaller initramfs images, you may want to specify
	the --hostonly 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
	--hostonly 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.

	=== Inspecting the Contents
	To see the contents of the image created by dracut, you can use the lsinitrd
	tool.
	----
	# lsinitrd \| less
	----

	To display the contents of a file in the initramfs also use the lsinitrd tool:
	----
	# lsinitrd -f /etc/ld.so.conf
	include ld.so.conf.d/*.conf
	----

	=== Adding dracut Modules
	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 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, use the --list-modules option:
	----
	# dracut --list-modules
	----

	=== Omitting dracut Modules
	Sometimes 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 dracut.conf(5)), or use the -o or --omit option
	on the command line:
	----
	# dracut -o "multipath lvm" no-multipath-lvm.img
	----

	=== Adding Kernel Modules
	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 dracut.conf(5)):
	----
	# dracut --add-drivers mymod initramfs-with-mymod.img
	----

	=== Boot parameters
	An initramfs generated without the "hostonly" mode, 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_ or
	_/boot/grub2/grub.cfg_, 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 <<NetworkBoot>>.

	For a full reference of all kernel command line parameters,
	see dracut.cmdline(5).

	To get a quick start for the suitable kernel command line on your system,
	use the __--print-cmdline__ option:
	----
	# dracut --print-cmdline
	root=UUID=8b8b6f91-95c7-4da2-831b-171e12179081 rootflags=rw,relatime,discard,data=ordered rootfstype=ext4
	----

	==== Specifying the root Device
	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 <<NetworkBoot>>.

	==== Keyboard Settings
	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:
	----
	rd.vconsole.font=latarcyrheb-sun16 rd.vconsole.keymap=de-latin1-nodeadkeys rd.locale.LANG=de_DE.UTF-8
	----

	Setting these options can override the setting stored on your system, if you use
	a modern init system, like systemd.

	==== Blacklisting Kernel Modules
	Sometimes it is required to prevent the automatic kernel module loading of a
	specific kernel module. To do this, just add rd.blacklist=_++<kernel module
	name>++_, with _++<kernel module name>++_ not containing the _.ko_
	suffix, to the kernel command line. For example:
	----
	rd.driver.blacklist=mptsas rd.driver.blacklist=nouveau
	----

	The option can be specified multiple times on the kernel command line.

	==== Speeding up the Boot Process
	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.luks=0 rd.lvm=0 rd.md=0 rd.dm=0
	----

	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.


	[[Injecting]]
	=== Injecting custom Files
	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.d/mycmdline.conf initramfs-cmdline-pre.img
	----
	will create an initramfs image, where the file cmdline-preset will be copied
	inside the initramfs to _/etc/cmdline.d/mycmdline.conf_. --include can only
	be specified once.


	----
	# mkdir -p rd.live.overlay/etc/cmdline.d
	# mkdir -p rd.live.overlay/etc/conf.d
	# echo "ip=dhcp" >> rd.live.overlay/etc/cmdline.d/mycmdline.conf
	# echo export FOO=testtest >> rd.live.overlay/etc/conf.d/testvar.conf
	# echo export BAR=testtest >> rd.live.overlay/etc/conf.d/testvar.conf
	# tree rd.live.overlay/
	rd.live.overlay/
	`-- etc
	\|-- cmdline.d
	\| `-- mycmdline.conf
	`-- conf.d
	`-- testvar.conf

	# dracut --include rd.live.overlay / initramfs-rd.live.overlay.img
	----

	This will put the contents of the rd.live.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.


	[[NetworkBoot]]
	=== Network Boot

	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.

	If you specify ip=dhcp 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.d/mycmdline.conf_, with a
	method described in <<Injecting>>.

	==== Reducing the Image Size

	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.


	== Troubleshooting

	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:
	https://www.kernel.org/pub/linux/utils/boot/dracut/dracut.html


	[[identifying-your-problem-area]]
	=== Identifying your problem area
	. Remove ''rhgb'' and ''quiet'' from the kernel command line
	. Add ''rd.shell'' to the kernel command line. This will present a shell should
	dracut be unable to locate your root device
	. Add ''rd.shell rd.debug log_buf_len=1M'' to the kernel command line so that
	dracut shell commands are printed as they are executed
	. The file /run/initramfs/rdsosreport.txt is generated,
	which contains all the logs and the output of all significant tools, which are
	mentioned later.

	If you want to save that output, simply mount /boot by hand or insert an USB
	stick and mount that. Then you can store the output for later inspection.

	[[information-to-include-in-your-report]]
	=== Information to include in your report

	[[all-bug-reports]]
	==== All bug reports
	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.
	* Turn on dracut debugging (see _the 'debugging dracut' section_), and attach
	the file /run/initramfs/rdsosreport.txt.
	* If you use a dracut configuration file, please include _/etc/dracut.conf_ and
	all files in _/etc/dracut.conf.d/*.conf_

	[[network-root-device-related-problems]]
	==== Network root device related problems
	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 <<all-bug-reports>>, include the
	following information:


	* Please include the output of
	+
	----
	# /sbin/ifup <interfacename>
	# ip addr show
	----

	[[debugging-dracut]]
	=== Debugging dracut


	[[configure-a-serial-console]]
	==== Configure a serial console

	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.conf_ for editing. Below the line ''timeout=5'', add
	the following:
	+
	----
	serial --unit=0 --speed=9600
	terminal --timeout=5 serial console
	----
	+
	. Also in _/etc/grub.conf_, add the following boot arguemnts to the ''kernel''
	line:
	+
	----
	console=tty0 console=ttyS0,9600
	----
	+
	. When finished, the _/etc/grub.conf_ file 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.img
	----
	+
	. More 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
	+
	--
	NOTE: 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
	----
	--

	[[using-the-dracut-shell]]
	==== Using the dracut shell

	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 ''rd.shell'' to your bootloader configuration file
	(e.g. _/etc/grub.conf_)
	. Remove the boot arguments ''rhgb'' and ''quiet''
	+
	A sample _/etc/grub.conf_ bootloader 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 rd.shell
	initrd /dracut-2.6.29.5-191.fc11.x86_64.img
	----
	+
	. If system boot fails, you will be dropped into a shell as seen in the example
	below.
	+
	----
	No root device found
	Dropping to debug shell.

	#
	----
	+
	. Use this shell prompt to gather the information requested above
	(see <<all-bug-reports>>).

	[[accessing-the-root-volume-from-the-dracut-shell]]
	==== Accessing the root volume from the dracut shell
	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.example: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 lvm
	----
	+
	. You recall that your root volume was a LVM logical volume. Scan and activate
	any logical volumes.
	+
	----
	# lvm vgscan
	# lvm vgchange -ay
	----
	+
	. You 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
	----

	[[additional-dracut-boot-parameters]]
	==== Additional dracut boot parameters
	For more debugging options, see dracut.cmdline(7).


	[[debugging-dracut-on-shutdown]]
	==== Debugging dracut on shutdown

	To debug the shutdown sequence on systemd systems, you can _rd.break_
	on _pre-shutdown_ or _shutdown_.

	To do this from an already booted system:
	----
	# mkdir -p /run/initramfs/etc/cmdline.d
	# echo "rd.debug rd.break=pre-shutdown rd.break=shutdown" > /run/initramfs/etc/cmdline.d/debug.conf
	# touch /run/initramfs/.need_shutdown
	----

	This will give you a dracut shell after the system pivot'ed back in the
	initramfs.