NAME<\/a> dracut \u2212 low\u2212level tool for generating an initramfs\/initrd image<\/p>\n dracut<\/b> [OPTION…<\/i>] [ Create an initramfs 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, mounting the root filesystem and booting into the real system.<\/p>\n At boot time, the kernel unpacks that archive into RAM disk, mounts and uses it as initial root file system. All finding of the root device happens in this early userspace.<\/p>\n Initramfs images are also called “initrd”.<\/p>\n For a complete list of kernel command line options see dracut.cmdline<\/b>(7).<\/p>\n If you are dropped to an emergency shell, while booting your initramfs, the file \/run\/initramfs\/rdsosreport.txt<\/i> 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<\/b> to the kernel command line. \/run\/initramfs\/rdsosreport.txt<\/i> contains all logs and the output of some tools. It should be attached to any report about dracut problems.<\/p>\n To create a initramfs image, the most simple command is:<\/p>\n # dracut<\/p>\n 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\/initrd\u2212 If the initramfs image already exists, dracut will display an error message, and to overwrite the existing image, you have to use the \u2212\u2212force option.<\/p>\n # dracut \u2212\u2212force<\/p>\n If you want to specify another filename for the resulting image you would issue a command like:<\/p>\n # dracut foobar.img<\/p>\n To generate an image for a specific kernel version, the command would be:<\/p>\n # dracut foobar.img 2.6.40\u22121.rc5.f20<\/p>\n A shortcut to generate the image at the default location for a specific kernel version is:<\/p>\n # dracut \u2212\u2212kver 2.6.40\u22121.rc5.f20<\/p>\n If you want to create lighter, smaller initramfs images, you may want to specify the \u2212\u2212hostonly or \u2212H 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\u2019t put the disk on another controller or machine, and that you can\u2019t switch to another root filesystem, without recreating the initramfs image. The usage of the \u2212\u2212hostonly 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.<\/p>\n Inspecting the Contents<\/b> # lsinitrd | less<\/p>\n To display the contents of a file in the initramfs also use the lsinitrd tool:<\/p>\n # lsinitrd \u2212f \/etc\/ld.so.conf Adding dracut Modules<\/b> # dracut \u2212\u2212add bootchart initramfs\u2212bootchart.img<\/p>\n To see a list of available dracut modules, use the \u2212\u2212list\u2212modules option:<\/p>\n # dracut \u2212\u2212list\u2212modules<\/p>\n Omitting dracut Modules<\/b> # dracut \u2212o “multipath lvm” no\u2212multipath\u2212lvm.img<\/p>\n Adding Kernel Modules<\/b> # dracut \u2212\u2212add\u2212drivers mymod initramfs\u2212with\u2212mymod.img<\/p>\n Boot parameters<\/b> The kernel command line can also be provided by the dhcp server with the root\u2212path option. See the section called \u201cNetwork Boot\u201d.<\/p>\n For a full reference of all kernel command line parameters, see dracut.cmdline<\/b>(5).<\/p>\n To get a quick start for the suitable kernel command line on your system, use the \u2212\u2212print\u2212cmdline<\/i> option:<\/p>\n # dracut \u2212\u2212print\u2212cmdline Specifying the root Device<\/big><\/b><\/p>\n 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= root=\/dev\/sda2<\/p>\n 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:<\/p>\n root=UUID=19e9dda3\u22125a38\u2212484d\u2212a9b0\u2212fa6b067d0331<\/p>\n or<\/p>\n root=LABEL=myrootpartitionlabel<\/p>\n To see all UUIDs or LABELs on your system, do:<\/p>\n # ls \u2212l \/dev\/disk\/by\u2212uuid<\/p>\n or<\/p>\n # ls \u2212l \/dev\/disk\/by\u2212label<\/p>\n If your root partition is on the network see the section called \u201cNetwork Boot\u201d.<\/p>\n Keyboard Settings<\/big><\/b><\/p>\n If you have to input passwords for encrypted disk volumes, you might want to set the keyboard layout and specify a display font.<\/p>\n A typical german kernel command line would contain:<\/p>\n rd.vconsole.font=eurlatgr rd.vconsole.keymap=de\u2212latin1\u2212nodeadkeys rd.locale.LANG=de_DE.UTF\u22128<\/p>\n Setting these options can override the setting stored on your system, if you use a modern init system, like systemd.<\/p>\n Blacklisting Kernel Modules<\/big><\/b><\/p>\n Sometimes it is required to prevent the automatic kernel module loading of a specific kernel module. To do this, just add rd.blacklist= rd.driver.blacklist=mptsas rd.driver.blacklist=nouveau<\/p>\n The option can be specified multiple times on the kernel command line.<\/p>\n Speeding up the Boot Process<\/big><\/b><\/p>\n 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:<\/p>\n rd.luks=0 rd.lvm=0 rd.md=0 rd.dm=0<\/p>\n This turns off every automatic assembly of LVM, MD raids, DM raids and crypto LUKS.<\/p>\n Of course, you could also omit the dracut modules in the initramfs creation process, but then you would lose the possibility to turn it on on demand.<\/p>\n Injecting custom Files<\/b> The \u2212\u2212include option let you specify a source path and a target path. For example<\/p>\n # dracut \u2212\u2212include cmdline\u2212preset \/etc\/cmdline.d\/mycmdline.conf initramfs\u2212cmdline\u2212pre.img<\/p>\n will create an initramfs image, where the file cmdline\u2212preset will be copied inside the initramfs to \/etc\/cmdline.d\/mycmdline.conf<\/i>. \u2212\u2212include can only be specified once.<\/p>\n # mkdir \u2212p rd.live.overlay\/etc\/cmdline.d # dracut \u2212\u2212include rd.live.overlay \/ initramfs\u2212rd.live.overlay.img<\/p>\n This will put the contents of the rd.live.overlay directory into the root of the initramfs image.<\/p>\n The \u2212\u2212install 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.<\/p>\n # dracut \u2212\u2212install ‘strace fsck.ext3 ssh’ initramfs\u2212dbg.img<\/p>\n This will create an initramfs with the strace, fsck.ext3 and ssh executables, together with the libraries needed to start those. The \u2212\u2212install option can be specified multiple times.<\/p>\n Network Boot<\/b> If you specify ip=dhcp on the kernel command line, then dracut asks a dhcp server about the ip address for the machine. The dhcp server can also serve an additional root\u2212path, 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\u2019t pass a kernel command line, then you can inject \/etc\/cmdline.d\/mycmdline.conf<\/i>, with a method described in the section called \u201cInjecting custom Files\u201d.<\/p>\n Reducing the Image Size<\/big><\/b><\/p>\n To reduce the size of the initramfs, you should create it with by omitting all dracut modules, which you know, you don\u2019t need to boot the machine.<\/p>\n You can also specify the exact dracut and kernel modules to produce a very tiny initramfs image.<\/p>\n For example for a NFS image, you would do:<\/p>\n # dracut \u2212m “nfs network base” initramfs\u2212nfs\u2212only.img<\/p>\n 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 \u2212\u2212host\u2212only option:<\/p>\n # dracut \u2212m “nfs network base” \u2212\u2212host\u2212only initramfs\u2212nfs\u2212host\u2212only.img<\/p>\n This will reduce the size of the initramfs image significantly.<\/p>\n 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<\/font><\/b><\/p>\n Identifying your problem area<\/font><\/b><\/p>\n 1. Remove ‘rhgb<\/i>‘ and ‘quiet<\/i>‘ from the kernel command line<\/font><\/p>\n 2. Add ‘rd.shell<\/i>‘ to the kernel command line. This will present a shell should dracut be unable to locate your root device<\/font><\/p>\n 3. Add ‘rd.shell rd.debug log_buf_len=1M<\/i>‘ to the kernel command line so that dracut shell commands are printed as they are executed<\/font><\/p>\n 4. The file \/run\/initramfs\/rdsosreport.txt is generated, which contains all the logs and the output of all significant tools, which are mentioned later.<\/font><\/p>\n 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.<\/font><\/p>\n Information to include in your report In all cases, the following should be mentioned and attached to your bug report:<\/font><\/p>\n \u2022 The exact kernel command\u2212line used. Typically from the bootloader configuration file (e.g. \/boot\/grub2\/grub.cfg<\/i>) or from \/proc\/cmdline<\/i>.<\/font><\/p>\n \u2022 A copy of your disk partition information from \/etc\/fstab<\/i>, which might be obtained booting an old working initramfs or a rescue medium.<\/font><\/p>\n \u2022 Turn on dracut debugging (see the debugging dracut section<\/i>), and attach the file \/run\/initramfs\/rdsosreport.txt.<\/font><\/p>\n \u2022 If you use a dracut configuration file, please include \/etc\/dracut.conf<\/i> and all files in \/etc\/dracut.conf.d\/*.conf<\/i><\/font><\/p>\n Network root device related problems<\/big><\/b><\/font><\/p>\n 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 \u201cAll bug reports\u201d, include the following information:<\/font><\/p>\n \u2022 Please include the output of<\/font><\/p>\n # \/sbin\/ifup Debugging dracut 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.<\/font><\/p>\n 1. First, enable serial console output for both the kernel and the bootloader.<\/font><\/p>\n 2. Open the file \/boot\/grub2\/grub.cfg<\/i> for editing. Below the line ‘timeout=5<\/i>‘, add the following:<\/font><\/p>\n serial \u2212\u2212unit=0 \u2212\u2212speed=9600 3. Also in \/boot\/grub2\/grub.cfg<\/i>, add the following boot arguments to the ‘kernel<\/i>‘ line:<\/font><\/p>\n console=tty0 console=ttyS0,9600<\/font><\/p>\n 4. When finished, the \/boot\/grub2\/grub.cfg<\/i> file should look similar to the example below.<\/font><\/p>\n default=0 5. More detailed information on how to configure the kernel for console output can be found at<\/font> http:\/\/www.faqs.org\/docs\/Linux\u2212HOWTO\/Remote\u2212Serial\u2212Console\u2212HOWTO.html#CONFIGURE\u2212KERNEL<\/font><\/b>.<\/font><\/p>\n 6. Redirecting non\u2212interactive output<\/font><\/p>\n Note<\/big><\/b> # exec >\/dev\/kmsg 2>&1 <\/dev\/console<\/font><\/p>\n Using the dracut shell<\/big><\/b><\/font><\/p>\n dracut offers a shell for interactive debugging in the event dracut fails to locate your root filesystem. To enable the shell:<\/big><\/font><\/p>\n 1. Add the boot parameter ‘rd.shell<\/i>‘ to your bootloader configuration file (e.g. \/boot\/grub2\/grub.cfg<\/i>)<\/big><\/font><\/p>\n 2. Remove the boot arguments ‘rhgb<\/i>‘ and ‘quiet<\/i>‘<\/big><\/font><\/p>\n A sample \/boot\/grub2\/grub.cfg<\/i> bootloader configuration file is listed below.<\/big><\/font><\/p>\n default=0 3. If system boot fails, you will be dropped into a shell as seen in the example below.<\/big><\/font><\/p>\n No root device found #<\/big><\/font><\/p>\n 4. Use this shell prompt to gather the information requested above (see the section called \u201cAll bug reports\u201d).<\/big><\/font><\/p>\n Accessing the root volume from the dracut shell<\/big><\/b><\/big><\/font><\/p>\n 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:<\/big><\/font><\/p>\n \u2022 A block device (e.g. \/dev\/sda7<\/i>)<\/big><\/font><\/p>\n \u2022 A LVM logical volume (e.g. \/dev\/VolGroup00\/LogVol00<\/i>)<\/big><\/font><\/p>\n \u2022 An encrypted device (e.g. \/dev\/mapper\/luks\u22124d5972ea\u2212901c\u22124584\u2212bd75\u22121da802417d83<\/i>)<\/big><\/font><\/p>\n \u2022 A network attached device (e.g. netroot=iscsi:@192.168.0.4::3260::iqn.2009\u221202.org.example:for.all<\/i>)<\/big><\/font><\/p>\n 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<\/i> 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.<\/big><\/font><\/p>\n 1. Inspect your partitions using parted<\/big><\/font><\/p>\n # parted \/dev\/sda \u2212s p 2. You recall that your root volume was a LVM logical volume. Scan and activate any logical volumes.<\/big><\/font><\/p>\n # lvm vgscan 3. You should see any logical volumes now using the command blkid:<\/big><\/font><\/p>\n # blkid 4. 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.<\/big><\/font><\/p>\n # UUID=$(cryptsetup luksUUID \/dev\/mapper\/linux\u2212root) 5. Next, make a symbolic link to the unlocked root volume<\/big><\/font><\/p>\n # ln \u2212s \/dev\/mapper\/luks\u2212$UUID \/dev\/root<\/big><\/font><\/p>\n 6. With the root volume available, you may continue booting the system by exiting the dracut shell<\/big><\/font><\/p>\n # exit<\/big><\/font><\/p>\n Additional dracut boot parameters<\/big><\/b><\/big><\/font><\/p>\n For more debugging options, see dracut.cmdline<\/b>(7).<\/big><\/font><\/p>\n Debugging dracut on shutdown<\/big><\/b><\/big><\/font><\/p>\n To debug the shutdown sequence on systemd systems, you can rd.break<\/i> on pre\u2212shutdown<\/i> or shutdown<\/i>.<\/big><\/font><\/p>\n To do this from an already booted system:<\/big><\/font><\/p>\n # mkdir \u2212p \/run\/initramfs\/etc\/cmdline.d
SYNOPSIS<\/a>
DESCRIPTION<\/a>
USAGE<\/a>
TROUBLESHOOTING<\/a>
OPTIONS<\/a>
ENVIRONMENT<\/a>
FILES<\/a>
AVAILABILITY<\/a>
AUTHORS<\/a>
SEE ALSO<\/a> <\/p>\n
\nNAME <\/a> <\/h2>\n
SYNOPSIS <\/a> <\/h2>\n
DESCRIPTION <\/a> <\/h2>\n
USAGE <\/a> <\/h2>\n
To see the contents of the image created by dracut, you can use the lsinitrd tool.<\/p>\n
include ld.so.conf.d\/*.conf<\/p>\n
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<\/i> or \/etc\/dracut.conf.d\/myconf.conf<\/i>. See dracut.conf<\/b>(5). You can also add dracut modules on the command line by using the \u2212a or \u2212\u2212add option:<\/p>\n
Sometimes you don\u2019t 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<\/i> or \/etc\/dracut.conf.d\/myconf.conf<\/i> configuration file (see dracut.conf<\/b>(5)), or use the \u2212o or \u2212\u2212omit option on the command line:<\/p>\n
If you need a special kernel module in the initramfs, which is not automatically picked up by dracut, you have the use the \u2212\u2212add\u2212drivers option on the command line or the drivers variable in the \/etc\/dracut.conf<\/i> or \/etc\/dracut.conf.d\/myconf.conf<\/i> configuration file (see dracut.conf<\/b>(5)):<\/p>\n
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 completely 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.<\/p>\n
root=UUID=8b8b6f91\u221295c7\u22124da2\u2212831b\u2212171e12179081 rootflags=rw,relatime,discard,data=ordered rootfstype=ext4<\/p>\n
To add your own files to the initramfs image, you have several possibilities.<\/p>\n
# mkdir \u2212p 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\/
\u2018\u2212\u2212 etc
|\u2212\u2212 cmdline.d
| \u2018\u2212\u2212 mycmdline.conf
\u2018\u2212\u2212 conf.d
\u2018\u2212\u2212 testvar.conf<\/p>\n
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.<\/p>\nTROUBLESHOOTING <\/a> <\/h2>\n
All bug reports<\/big><\/b><\/font><\/p>\n
# ip addr show<\/font><\/p>\n
Configure a serial console<\/big><\/b><\/font><\/p>\n
terminal \u2212\u2212timeout=5 serial console<\/font><\/p>\n
timeout=5
serial \u2212\u2212unit=0 \u2212\u2212speed=9600
terminal \u2212\u2212timeout=5 serial console
title Fedora (2.6.29.5\u2212191.fc11.x86_64)
root (hd0,0)
kernel \/vmlinuz\u22122.6.29.5\u2212191.fc11.x86_64 ro root=\/dev\/mapper\/vg_uc1\u2212lv_root console=tty0 console=ttyS0,9600
initrd \/dracut\u22122.6.29.5\u2212191.fc11.x86_64.img<\/font><\/p>\n
You can redirect all non\u2212interactive output to \/dev\/kmsg<\/i> and the kernel will put it out on the console when it reaches the kernel buffer by doing<\/font><\/p>\n
timeout=5
serial \u2212\u2212unit=0 \u2212\u2212speed=9600
terminal \u2212\u2212timeout=5 serial console
title Fedora (2.6.29.5\u2212191.fc11.x86_64)
root (hd0,0)
kernel \/vmlinuz\u22122.6.29.5\u2212191.fc11.x86_64 ro root=\/dev\/mapper\/vg_uc1\u2212lv_root console=tty0 rd.shell
initrd \/dracut\u22122.6.29.5\u2212191.fc11.x86_64.img<\/big><\/font><\/p>\n
Dropping to debug shell.<\/big><\/font><\/p>\n
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<\/big><\/font><\/p>\n
# lvm vgchange \u2212ay<\/big><\/font><\/p>\n
\/dev\/sda1: UUID=”3de247f3\u22125de4\u22124a44\u2212afc5\u22121fe179750cf7″ TYPE=”ext4″
\/dev\/sda2: UUID=”Ek4dQw\u2212cOtq\u22125MJu\u2212OGRF\u2212xz5k\u2212O2l8\u2212wdDj0I” TYPE=”LVM2_member”
\/dev\/mapper\/linux\u2212root: UUID=”def0269e\u2212424b\u22124752\u2212acf3\u22121077bf96ad2c” TYPE=”crypto_LUKS”
\/dev\/mapper\/linux\u2212home: UUID=”c69127c1\u2212f153\u22124ea2\u2212b58e\u22124cbfa9257c5e” TYPE=”ext3″
\/dev\/mapper\/linux\u2212swap: UUID=”47b4d329\u2212975c\u22124c08\u2212b218\u2212f9c9bf3635f1″ TYPE=”swap”<\/big><\/font><\/p>\n
# cryptsetup luksOpen \/dev\/mapper\/linux\u2212root luks\u2212$UUID
Enter passphrase for \/dev\/mapper\/linux\u2212root:
Key slot 0 unlocked.<\/big><\/font><\/p>\n
# echo “rd.debug rd.break=pre\u2212shutdown rd.break=shutdown” > \/run\/initramfs\/etc\/cmdline.d\/debug.conf
# touch \/run\/initramfs\/.need_shutdown<\/big><\/font><\/p>\n