# dracut 057

### Harald Hoyer

`<harald@profian.com>`

# Part I. Introduction

This section is a modified version of http://en.wikipedia.org/wiki/Initrd which is licensed under the Creative Commons Attribution/Share-Alike License.

## Chapter 1. Definition

An initial ramdisk is a temporary file system used in the boot process of the Linux kernel. initrd and initramfs refer to slightly different schemes for loading this file system into memory. Both are commonly used to make preparations before the real root file system can be mounted.

## Chapter 2. Rationale

Many Linux distributions ship a single, generic kernel image that is intended to boot as wide a variety of hardware as possible. The device drivers for this generic kernel image are included as loadable modules, as it is not possible to statically compile them all into the one kernel without making it too large to boot from computers with limited memory or from lower-capacity media like floppy disks.

This then raises the problem of detecting and loading the modules necessary to mount the root file system at boot time (or, for that matter, deducing where or what the root file system is).

To further complicate matters, the root file system may be on a software RAID volume, LVM, NFS (on diskless workstations), or on an encrypted partition. All of these require special preparations to mount.

Another complication is kernel support for hibernation, which suspends the computer to disk by dumping an image of the entire system to a swap partition or a regular file, then powering off. On next boot, this image has to be made accessible before it can be loaded back into memory.

To avoid having to hardcode handling for so many special cases into the kernel, an initial boot stage with a temporary root file system —now dubbed early user space— is used. This root file system would contain user-space helpers that would do the hardware detection, module loading and device discovery necessary to get the real root file system mounted.

## Chapter 3. Implementation

An image of this initial root file system (along with the kernel image) must be stored somewhere accessible by the Linux bootloader or the boot firmware of the computer. This can be:

- The root file system itself
- A boot image on an optical disc
- A small ext2/ext3 or FAT-formatted partition on a local disk (a boot partition)
- A TFTP server (on systems that can boot from Ethernet)

The bootloader will load the kernel and initial root file system image into memory and then start the kernel, passing in the memory address of the image.

Depending on which algorithms were compiled statically into it, the kernel can currently unpack initrd/initramfs images compressed with gzip, bzip2 and LZMA.

## Chapter 4. Mount preparations

dracut can generate a customized initramfs image which contains only whatever is necessary to boot some particular computer, such as ATA, SCSI and filesystem kernel modules (host-only mode).

dracut can also generate a more generic initramfs image (default mode).

dracut’s initramfs starts only with the device name of the root file system (or its UUID) and must discover everything else at boot time. A complex cascade of tasks must be performed to get the root file system mounted:

- Any hardware drivers that the boot process depends on must be loaded. All kernel modules for common storage devices are packed onto the initramfs and then udev pulls in modules matching the computer’s detected hardware.
- On systems which display a boot rd.splash screen, the video hardware must be initialized and a user-space helper started to paint animations onto the display in lockstep with the boot process.

- If the root file system is on NFS, dracut does then:

  - Bring up the primary network interface.
  - Invoke a DHCP client, with which it can obtain a DHCP lease.
  - Extract the name of the NFS share and the address of the NFS server from the lease.
  - Mount the NFS share.
- If the root file system appears to be on a software RAID device, there is no way of knowing which devices the RAID volume spans; the standard MD utilities must be invoked to scan all available block devices with a raid signature and bring the required ones online.
- If the root file system appears to be on a logical volume, the LVM utilities must be invoked to scan for and activate the volume group containing it.

- If the root file system is on an encrypted block device:

  - Invoke a helper script to prompt the user to type in a passphrase and/or insert a hardware token (such as a smart card or a USB security dongle).
- Create a decryption target with the device mapper.

dracut uses udev, an event-driven hotplug agent, which invokes helper programs as hardware devices, disk partitions and storage volumes matching certain rules come online. This allows discovery to run in parallel, and to progressively cascade into arbitrary nestings of LVM, RAID or encryption to get at the root file system.

When the root file system finally becomes visible:

- Any maintenance tasks which cannot run on a mounted root file system are done.
- The root file system is mounted read-only.
- Any processes which must continue running (such as the rd.splash screen helper and its command FIFO) are hoisted into the newly-mounted root file system.

The final root file system cannot simply be mounted over /, since that would make the scripts and tools on the initial root file system inaccessible for any final cleanup tasks. On an initramfs, the initial root file system cannot be rotated away. Instead, it is simply emptied and the final root file system mounted over the top.

If the systemd module is used in the initramfs, the ordering of the services started looks like Chapter 12, DRACUT.BOOTUP(7).

## Chapter 5. Dracut on shutdown

On a systemd driven system, the dracut initramfs is also used for the shutdown procedure.

The following steps are executed during a shutdown:

- systemd switches to the shutdown.target
- systemd starts $prefix/lib/systemd/system/shutdown.target.wants/dracut-shutdown.service
- dracut-shutdown.service executes /usr/lib/dracut/dracut-initramfs-restore which unpacks the initramfs to /run/initramfs
- systemd finishes shutdown.target
- systemd kills all processes
- systemd tries to unmount everything and mounts the remaining read-only
- systemd checks, if there is a /run/initramfs/shutdown executable
- if yes, it does a pivot_root to /run/initramfs and executes ./shutdown. The old root is then mounted on /oldroot. /usr/lib/dracut/modules.d/99shutdown/shutdown.sh is the shutdown executable.
- shutdown will try to unmount every /oldroot mount and calls the various shutdown hooks from the dracut modules

This ensures, that all devices are disassembled and unmounted cleanly.

# Part II. User Manual

## Chapter 6. DRACUT(8)

## NAME

dracut - low-level tool for generating an initramfs/initrd image

## SYNOPSIS

dracut [OPTION…] [<image> [<kernel version>]]

## DESCRIPTION

Create an initramfs <image> for the kernel with the version <kernel version>. If <kernel version> is omitted, then the version of the actual running kernel is used. If <image> is omitted or empty, depending on bootloader specification, the default location can be /efi/<machine-id>/<kernel-version>/initrd, /boot/<machine-id>/<kernel-version>/initrd, /boot/efi/<machine-id>/<kernel-version>/initrd, /lib/modules/<kernel-version>/initrd or /boot/initramfs-<kernel-version>.img.

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.

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.

Initramfs images are also called "initrd".

For a complete list of kernel command line options see dracut.cmdline(7).

If you are dropped to an emergency shell, while booting your initramfs, 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.

## USAGE

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, depending on bootloader specification, can be /efi/`<machine-id>`/`<kernel-version>`/initrd, /boot/`<machine-id>`/`<kernel-version>`/initrd, /boot/efi/`<machine-id>`/`<kernel-version>`/initrd, /lib/modules/`<kernel-version>`/initrd or /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 module initramfs-module.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 variable 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 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.

The kernel command line can also be provided by the dhcp server with the root-path option. See the section called “Network Boot”.

For a full reference of all kernel command line parameters, see dracut.cmdline(7).

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 the section called “Network Boot”.

#### 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 line would contain:

    rd.vconsole.font=eurlatgr 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 possibility to turn it on on demand.

### 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.

### 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 address 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 the section called “Injecting custom Files”.

#### Reducing the Image Size

To reduce the size of the initramfs, you should create it with by omitting 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

1. Remove 'rhgb' and 'quiet' from the kernel command line
2. Add 'rd.shell' to the kernel command line. This will present a shell should dracut be unable to locate your root device
3. 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
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.

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

#### 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. /boot/grub2/grub.cfg) 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

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 “All bug reports”, include the following information:

- Please include the output of

      # /sbin/ifup <interfacename>
      # ip addr show

### Debugging dracut

#### 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.

1. First, enable serial console output for both the kernel and the bootloader.

2. Open the file /boot/grub2/grub.cfg for editing. Below the line 'timeout=5', add the following:

       serial --unit=0 --speed=9600
       terminal --timeout=5 serial console

3. Also in /boot/grub2/grub.cfg, add the following boot arguments to the 'kernel' line:

       console=tty0 console=ttyS0,9600

4. When finished, the /boot/grub2/grub.cfg 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

5. 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.

6. 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

dracut offers a shell for interactive debugging in the event dracut fails to locate your root filesystem. To enable the shell:

1. Add the boot parameter 'rd.shell' to your bootloader configuration file (e.g. /boot/grub2/grub.cfg)

2. Remove the boot arguments 'rhgb' and 'quiet'

   A sample /boot/grub2/grub.cfg 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

3. 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.

       #

4. Use this shell prompt to gather the information requested above (see the section called “All bug reports”).

#### 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.

1. 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

2. You recall that your root volume was a LVM logical volume. Scan and activate any logical volumes.

       # lvm vgscan
       # lvm vgchange -ay

3. 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"

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.

       # 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.

5. Next, make a symbolic link to the unlocked root volume

       # ln -s /dev/mapper/luks-$UUID /dev/root

6. With the root volume available, you may continue booting the system by exiting the dracut shell

       # exit

#### Additional dracut boot parameters

For more debugging options, see dracut.cmdline(7).

#### 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.

## OPTIONS

--kver <kernel version>
  Set the kernel version. This enables to specify the kernel version, without specifying the location of the initramfs image. For example:

    # dracut --kver 3.5.0-0.rc7.git1.2.fc18.x86_64

-f, --force
  Overwrite existing initramfs file.
<output file> --rebuild
  Append the current arguments to those with which the input initramfs image was built. This option helps in incrementally building the initramfs for testing. If optional <output file> is not provided, the input initramfs provided to rebuild will be used as output file.
-a, --add <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.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --add "module1 module2"  ...

--force-add <list of dracut modules>

  Force to add a space-separated list of dracut modules to the default set of modules, when -H is specified. This parameter can be specified multiple times.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --force-add "module1 module2"  ...

-o, --omit <list of dracut modules>

  Omit a space-separated list of dracut modules. This parameter can be specified multiple times.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --omit "module1 module2"  ...

-m, --modules <list of dracut modules>

  Specify a space-separated list of dracut modules to call when building the initramfs. Modules are located in /usr/lib/dracut/modules.d. This parameter can be specified multiple times. This option forces dracut to only include the specified dracut modules. In most cases the "--add" option is what you want to use.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --modules "module1 module2"  ...

-d, --drivers <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.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --drivers "kmodule1 kmodule2"  ...

--add-drivers <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.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --add-drivers "kmodule1 kmodule2"  ...

--force-drivers <list of kernel modules>

  See add-drivers above. But in this case it is ensured that the drivers are tried to be loaded early via modprobe.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --force-drivers "kmodule1 kmodule2"  ...

--omit-drivers <list of kernel modules>

  Specify a space-separated list of kernel modules not to add to the initramfs. The kernel modules have to be specified without the ".ko" suffix. This parameter can be specified multiple times.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --omit-drivers "kmodule1 kmodule2"  ...

--filesystems <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.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --filesystems "filesystem1 filesystem2"  ...

-k, --kmoddir <kernel directory>
  Specify the directory, where to look for kernel modules.
--fwdir <dir>[:<dir>…]++
  Specify additional directories, where to look for firmwares. This parameter can be specified multiple times.
--libdirs <list of directories>

  Specify a space-separated list of directories to look for libraries to include in the generic initramfs. This parameter can be specified multiple times.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --libdirs "dir1 dir2"  ...

--kernel-cmdline <parameters>
  Specify default kernel command line parameters.
--kernel-only
  Only install kernel drivers and firmware files.
--no-kernel
  Do not install kernel drivers and firmware files.
--early-microcode
  Combine early microcode with ramdisk.
--no-early-microcode
  Do not combine early microcode with ramdisk.
--print-cmdline
  Print the kernel command line for the current disk layout.
--mdadmconf
  Include local /etc/mdadm.conf file.
--nomdadmconf
  Do not include local /etc/mdadm.conf file.
--lvmconf
  Include local /etc/lvm/lvm.conf file.
--nolvmconf
  Do not include local /etc/lvm/lvm.conf file.
--fscks <list of fsck tools>

  Add a space-separated list of fsck tools, in addition to dracut.conf's specification; the installation is opportunistic (non-existing tools are ignored).

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --fscks "fsck.foo barfsck"  ...

--nofscks
  Inhibit installation of any fsck tools.
--strip
  Strip binaries in the initramfs (default).
--aggresive-strip
  Strip more than just debug symbol and sections, for a smaller initramfs build. The --strip option must also be specified.
--nostrip
  Do not strip binaries in the initramfs.
--hardlink
  Hardlink files in the initramfs (default).
--nohardlink
  Do not hardlink files in the initramfs.
--prefix <dir>
  Prefix initramfs files with the specified directory.
--noprefix
  Do not prefix initramfs files (default).
-h, --help
  Display help text and exit.
--debug
  Output debug information of the build process.
-v, --verbose
  Increase verbosity level (default is info(4)).
--version
  Display version and exit.
-q, --quiet
  Decrease verbosity level (default is info(4)).
-c, --conf <dracut configuration file>

  Specify configuration file to use.

  Default: /etc/dracut.conf

--confdir <configuration directory>

  Specify configuration directory to use.

  Default: /etc/dracut.conf.d

--tmpdir <temporary directory>

  Specify temporary directory to use.

  Default: /var/tmp

-r, --sysroot <sysroot directory>

  Specify the sysroot directory to collect files from. This is useful to create the initramfs image from a cross-compiled sysroot directory. For the extra helper variables, see ENVIRONMENT below.

  Default: empty

--sshkey <sshkey file>
  SSH key file used with ssh-client module.
--logfile <logfile>

  Logfile to use; overrides any setting from the configuration files.

  Default: /var/log/dracut.log

-l, --local
  Activates the local mode. dracut will use modules from the current working directory instead of the system-wide installed modules in /usr/lib/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 and generate host-specific configuration.

  ### Warning

  If chrooted to another root other than the real root device, use "--fstab" and provide a valid /etc/fstab.

-N, --no-hostonly
  Disable host-only mode.
--hostonly-mode <mode>

  Specify the host-only mode to use. <mode> could be one of "sloppy" or "strict". In "sloppy" host-only mode, extra drivers and modules will be installed, so minor hardware change won’t make the image unbootable (e.g. changed keyboard), and the image is still portable among similar hosts. With "strict" mode enabled, anything not necessary for booting the local host in its current state will not be included, and modules may do some extra job to save more space. Minor change of hardware or environment could make the image unbootable.

  Default: sloppy

--hostonly-cmdline
  Store kernel command line arguments needed in the initramfs.
--no-hostonly-cmdline
  Do not store kernel command line arguments needed in the initramfs.
--no-hostonly-default-device
  Do not generate implicit host devices like root, swap, fstab, etc. Use "--mount" or "--add-device" to explicitly add devices as needed.
--hostonly-i18n
  Install only needed keyboard and font files according to the host configuration (default).
--no-hostonly-i18n
  Install all keyboard and font files available.
--hostonly-nics <list of nics>
  Only enable listed NICs in the initramfs. The list can be empty, so other modules can install only the necessary network drivers.
--persistent-policy <policy>
  Use <policy> to address disks and partitions. <policy> can be any directory name found in /dev/disk. E.g. "by-uuid", "by-label"
--fstab
  Use /etc/fstab instead of /proc/self/mountinfo.
--add-fstab <filename>
  Add entries of <filename> to the initramfs /etc/fstab.
--mount "<device> <mountpoint> <filesystem type> [<filesystem options> [<dump frequency> [<fsck order>]]]"
  Mount <device> on <mountpoint> with <filesystem type> in the initramfs. <filesystem options>, <dump options> and <fsck order> can be specified, see fstab manpage for the details. The default <filesystem options> is "defaults". The default <dump frequency> is "0". The default <fsck order> is "2".
--mount "<mountpoint>"
  Like above, but <device>, <filesystem type> and <filesystem options> are determined by looking at the current mounts.
--add-device <device>
  Bring up <device> in initramfs, <device> should be the device name. This can be useful in host-only mode for resume support when your swap is on LVM or an encrypted partition. [NB --device can be used for compatibility with earlier releases]
-i, --include <SOURCE> <TARGET>
  Include the files in the SOURCE directory into the TARGET directory in the final initramfs. If SOURCE is a file, it will be installed to TARGET in the final initramfs. This parameter can be specified multiple times.
-I, --install <file list>

  Install the space separated list of files into the initramfs.

  ### Note

  If the list has multiple arguments, then you have to put these in quotes. For example:

      # dracut --install "/bin/foo /sbin/bar"  ...

--install-optional <file list>
  Install the space separated list of files into the initramfs, if they exist.
--gzip
  Compress the generated initramfs using gzip. This will be done by default, unless another compression option or --no-compress is passed. Equivalent to "--compress=gzip -9".
--bzip2

  Compress the generated initramfs using bzip2.

  ### Warning

  Make sure your kernel has bzip2 decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=bzip2 -9".

--lzma

  Compress the generated initramfs using lzma.

  ### Warning

  Make sure your kernel has lzma decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=lzma -9 -T0".

--xz

  Compress the generated initramfs using xz.

  ### Warning

  Make sure your kernel has xz decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=xz --check=crc32 --lzma2=dict=1MiB -T0".

--lzo

  Compress the generated initramfs using lzop.

  ### Warning

  Make sure your kernel has lzo decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=lzop -9".

--lz4

  Compress the generated initramfs using lz4.

  ### Warning

  Make sure your kernel has lz4 decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=lz4 -l -9".

--zstd

  Compress the generated initramfs using Zstandard.

  ### Warning

  Make sure your kernel has zstd decompression support compiled in, otherwise you will not be able to boot. Equivalent to "--compress=zstd -15 -q -T0".

--compress <compressor>
  Compress the generated initramfs using the passed compression program. If you pass it just the name of a compression program, it will call that program with known-working arguments. If you pass a quoted string with arguments, it will be called with exactly those arguments. Depending on what you pass, this may result in an initramfs that the kernel cannot decompress. The default value can also be set via the INITRD_COMPRESS environment variable.
--squash-compressor <compressor>
  Compress the squashfs image using the passed compressor and compressor specific options for mksquashfs. You can refer to mksquashfs manual for supported compressors and compressor specific options. If squash module is not called when building the initramfs, this option will not take effect.
--no-compress
  Do not compress the generated initramfs. This will override any other compression options.
--reproducible
  Create reproducible images.
--no-reproducible
  Do not create reproducible images.
--list-modules
  List all available dracut modules.
-M, --show-modules
  Print included module’s name to standard output during build.
--keep
  Keep the initramfs temporary directory for debugging purposes.
--printsize
  Print out the module install size.
--profile
  Output profile information of the build process.
--ro-mnt
  Mount / and /usr read-only by default.
-L, --stdlog <level>
  [0-6] Specify logging level (to standard error).

              0 - suppress any messages
              1 - only fatal errors
              2 - all errors
              3 - warnings
              4 - info
              5 - debug info (here starts lots of output)
              6 - trace info (and even more)

--regenerate-all
  Regenerate all initramfs images at the default location with the kernel versions found on the system. Additional parameters are passed through.
-p, --parallel
  Try to execute tasks in parallel. Currently only supported with --regenerate-all (build initramfs images for all kernel versions simultaneously).
--noimageifnotneeded
  Do not create an image in host-only mode, if no kernel driver is needed and no /etc/cmdline/*.conf will be generated into the initramfs.
--loginstall <directory>
  Log all files installed from the host to <directory>.
--uefi
  Instead of creating an initramfs image, dracut will create an UEFI executable, which can be executed by an UEFI BIOS. The default output filename is <EFI>/EFI/Linux/linux-$kernel$-<MACHINE_ID>-<BUILD_ID>.efi. <EFI> might be /efi, /boot or /boot/efi depending on where the ESP partition is mounted. The <BUILD_ID> is taken from BUILD_ID in /usr/lib/os-release or if it exists /etc/os-release and is left out, if BUILD_ID is non-existant or empty.
--no-uefi
  Disables UEFI mode.
--no-machineid
  Affects the default output filename of --uefi and will discard the <MACHINE_ID> part.
--uefi-stub <file>
  Specifies the UEFI stub loader, which will load the attached kernel, initramfs and kernel command line and boots the kernel. The default is $prefix/lib/systemd/boot/efi/linux<EFI-MACHINE-TYPE-NAME>.efi.stub.
--uefi-splash-image <file>
  Specifies the UEFI stub loader’s splash image. Requires bitmap (.bmp) image format.
--kernel-image <file>
  Specifies the kernel image, which to include in the UEFI executable. The default is /lib/modules/<KERNEL-VERSION>/vmlinuz or /boot/vmlinuz-<KERNEL-VERSION>.
--enhanced-cpio
  Attempt to use the dracut-cpio binary, which optimizes archive creation for copy-on-write filesystems by using the copy_file_range(2) syscall via Rust’s io::copy(). When specified, initramfs archives are also padded to ensure optimal data alignment for extent sharing. To retain reflink data deduplication benefits, this should be used alongside the --no-compress and --no-strip parameters, with initramfs source files, --tmpdir staging area and destination all on the same copy-on-write capable filesystem.

## ENVIRONMENT

INITRD_COMPRESS
  sets the default compression program. See --compress.
DRACUT_LDCONFIG

  sets the ldconfig program path and options. Optional. Used for --sysroot.

  Default: ldconfig

DRACUT_LDD

  sets the ldd program path and options. Optional. Used for --sysroot.

  Default: ldd

DRACUT_TESTBIN

  sets the initially tested binary for detecting library paths. Optional. Used for --sysroot. In the cross-compiled sysroot, the default value (/bin/sh) is unusable, as it is an absolute symlink and points outside the sysroot directory.

  Default: /bin/sh

DRACUT_INSTALL

  overrides path and options for executing dracut-install internally. Optional. Can be used to debug dracut-install while running the main dracut script.

  Default: dracut-install

  Example: DRACUT_INSTALL="valgrind dracut-install"

DRACUT_COMPRESS_BZIP2 , DRACUT_COMPRESS_BZIP2 , DRACUT_COMPRESS_LBZIP2 , DRACUT_COMPRESS_LZMA , DRACUT_COMPRESS_XZ , DRACUT_COMPRESS_GZIP , DRACUT_COMPRESS_PIGZ , DRACUT_COMPRESS_LZOP , DRACUT_COMPRESS_ZSTD , DRACUT_COMPRESS_LZ4 , DRACUT_COMPRESS_CAT

  overrides for compression utilities to support using them from non-standard paths.

  Default values are the default compression utility names to be found in PATH.

DRACUT_ARCH

  overrides the value of uname -m. Used for --sysroot.

  Default: empty (the value of uname -m on the host system)

SYSTEMD_VERSION
  overrides systemd version. Used for --sysroot.
SYSTEMCTL
  overrides the systemctl binary. Used for --sysroot.
NM_VERSION
  overrides the NetworkManager version. Used for --sysroot.
DRACUT_INSTALL_PATH

  overrides PATH environment for dracut-install to look for binaries relative to --sysroot. In a cross-compiled environment (e.g. Yocto), PATH points to natively built binaries that are not in the host’s /bin, /usr/bin, etc. dracut-install still needs plain /bin and /usr/bin that are relative to the cross-compiled sysroot.

  Default: PATH

DRACUT_INSTALL_LOG_TARGET

  overrides DRACUT_LOG_TARGET for dracut-install. It allows running dracut-install* to run with different log target that dracut** runs with.

  Default: DRACUT_LOG_TARGET

DRACUT_INSTALL_LOG_LEVEL

  overrides DRACUT_LOG_LEVEL for dracut-install. It allows running dracut-install* to run with different log level that dracut** runs with.

  Default: DRACUT_LOG_LEVEL

## FILES

/var/log/dracut.log
  logfile of initramfs image creation
/tmp/dracut.log
  logfile of initramfs image creation, if /var/log/dracut.log is not writable
/etc/dracut.conf
  see dracut.conf5
/etc/dracut.conf.d/*.conf
  see dracut.conf5
/usr/lib/dracut/dracut.conf.d/*.conf
  see dracut.conf5

### 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.

## AVAILABILITY

The dracut command is part of the dracut package and is available from https://dracut.wiki.kernel.org

## AUTHORS

Harald Hoyer

Victor Lowther

Amadeusz Żołnowski

Hannes Reinecke

Daniel Molkentin

Will Woods

Philippe Seewer

Warren Togami

## SEE ALSO

dracut.cmdline(7) dracut.conf(5) lsinitrd(1)

## Chapter 7. DRACUT.CONF(5)

## NAME

dracut.conf - configuration file(s) for dracut

## SYNOPSIS

/etc/dracut.conf /etc/dracut.conf.d/*.conf /usr/lib/dracut/dracut.conf.d/*.conf

## Description

dracut.conf is loaded during the initialisation phase of dracut. Command line parameter will override any values set here.

*.conf files are read from /usr/lib/dracut/dracut.conf.d and /etc/dracut.conf.d. Files with the same name in /etc/dracut.conf.d will replace files in /usr/lib/dracut/dracut.conf.d. The files are then read in alphanumerical order and will override 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.

dracut command line options will override any values set here.

Configuration files must have the extension .conf; other extensions are ignored.

add_dracutmodules+=" <dracut modules> "
  Add a space-separated list of dracut modules to call when building the initramfs. Modules are located in /usr/lib/dracut/modules.d.
force_add_dracutmodules+=" <dracut modules> "
  Force to add a space-separated list of dracut modules to the default set of modules, when host-only mode is specified. This parameter can be specified multiple times.
omit_dracutmodules+=" <dracut modules> "
  Omit a space-separated list of dracut modules to call when building the initramfs. Modules are located in /usr/lib/dracut/modules.d.
dracutmodules+=" <dracut modules> "
  Specify a space-separated list of dracut modules to call when building the initramfs. Modules are located in /usr/lib/dracut/modules.d. This option forces dracut to only include the specified dracut modules. In most cases the "add_dracutmodules" option is what you want to use.
add_drivers+=" <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.
force_drivers+=" <list of kernel modules> "
  See add_drivers above. But in this case it is ensured that the drivers are tried to be loaded early via modprobe.
omit_drivers+=" <kernel modules> "
  Specify a space-separated list of kernel modules not to add to the initramfs. The kernel modules have to be specified without the ".ko" suffix.
drivers+=" <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.
filesystems+=" <filesystem names> "
  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+=" :<dir>[:<dir> …] "
  Specify additional colon-separated list of directories where to look for firmware files.
libdirs+=" <dir>[ <dir> …] "
  Specify a space-separated list of directories where to look for libraries.
install_items+=" <file>[ <file> …] "
  Specify additional files to include in the initramfs, separated by spaces.
install_optional_items+=" <file>[ <file> …] "
  Specify additional files to include in the initramfs, separated by spaces, if they exist.
compress="{cat|bzip2|lzma|xz|gzip|lzo|lz4|zstd|<compressor [args …]>}"
  Compress the generated initramfs using the passed compression program. If you pass it just the name of a compression program, it will call that program with known-working arguments. If you pass arguments, it will be called with exactly those arguments. Depending on what you pass, this may result in an initramfs that the kernel cannot decompress. To disable compression, use "cat".
squash_compress="{<compressor [args …]>}"
  Compress the squashfs image using the passed compressor and compressor specific options for mksquashfs. You can refer to mksquashfs manual for supported compressors and compressor specific options. If squash module is not called when building the initramfs, this option will not take effect.
do_strip="{yes|no}"
  Strip binaries in the initramfs (default=yes).
aggresive_strip="{yes|no}"
  Strip more than just debug symbol and sections, for a smaller initramfs build. The "do_strip=yes" option must also be specified (default=no).
do_hardlink="{yes|no}"
  Hardlink files in the initramfs (default=yes).
prefix=" <directory> "
  Prefix initramfs files with <directory>.
hostonly="{yes|no}"
  Host-only mode: Install only what is needed for booting the local host instead of a generic host and generate host-specific configuration (default=no).
hostonly_mode="{sloppy|strict}"
  Specify the host-only mode to use (default=sloppy). In "sloppy" host-only mode, extra drivers and modules will be installed, so minor hardware change won’t make the image unbootable (e.g. changed keyboard), and the image is still portable among similar hosts. With "strict" mode enabled, anything not necessary for booting the local host in its current state will not be included, and modules may do some extra job to save more space. Minor change of hardware or environment could make the image unbootable.
hostonly_cmdline="{yes|no}"
  If set to "yes", store the kernel command line arguments needed in the initramfs. If hostonly="yes" and this option is not configured, it’s automatically set to "yes".
hostonly_nics+=" [<nic>[ <nic> …]] "
  Only enable listed NICs in the initramfs. The list can be empty, so other modules can install only the necessary network drivers.
persistent_policy="<policy>"
  Use <policy> to address disks and partitions. <policy> can be any directory name found in /dev/disk. E.g. "by-uuid", "by-label"
tmpdir="<temporary directory>"
  Specify temporary directory to use.

### Warning

If chrooted to another root other than the real root device, use --fstab and provide a valid /etc/fstab.

use_fstab="{yes|no}"
  Use /etc/fstab instead of /proc/self/mountinfo (default=no).
add_fstab+=" <filename> "
  Add entries of <filename> to the initramfs /etc/fstab.
add_device+=" <device> "
  Bring up <device> in initramfs, <device> should be the device name. This can be useful in host-only mode for resume support when your swap is on LVM an encrypted partition.
mdadmconf="{yes|no}"
  Include local /etc/mdadm.conf (default=no).
lvmconf="{yes|no}"
  Include local /etc/lvm/lvm.conf (default=no).
fscks=" <fsck tools> "
  Add a space-separated list of fsck tools. If nothing is specified, the default is: "umount mount /sbin/fsck* xfs_db xfs_check xfs_repair e2fsck jfs_fsck reiserfsck btrfsck". The installation is opportunistic (non-existing tools are ignored).
nofscks="{yes|no}"
  If specified, inhibit installation of any fsck tools (default=no).
ro_mnt="{yes|no}"
  Mount / and /usr read-only by default (default=no).
kernel_cmdline="parameters"
  Specify default kernel command line parameters.
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).
acpi_override="{yes|no}"
  [WARNING] ONLY USE THIS IF YOU KNOW WHAT YOU ARE DOING! Override BIOS provided ACPI tables. For further documentation read Documentation/acpi/initrd_table_override.txt in the kernel sources. Search for ACPI table files (must have .aml suffix) in acpi_table_dir= directory (see below) and add them to a separate uncompressed cpio archive. This cpio archive gets glued (concatenated, uncompressed one must be the first one) to the compressed cpio archive. The first, uncompressed cpio archive is for data which the kernel must be able to access very early (and cannot make use of uncompress algorithms yet) like microcode or ACPI tables (default=no).
acpi_table_dir="<dir>"
  Directory to search for ACPI tables if acpi_override= is set to yes.
early_microcode="{yes|no}"
  Combine early microcode with ramdisk (default=yes).
stdloglvl="{0-6}"
  Specify logging level for standard error (default=4).

### Note

Logging levels:

        0 - suppress any messages
        1 - only fatal errors
        2 - all errors
        3 - warnings
        4 - info
        5 - debug info (here starts lots of output)
        6 - trace info (and even more)

sysloglvl="{0-6}"
  Specify logging level for syslog (default=0).
fileloglvl="{0-6}"
  Specify logging level for logfile (default=4).
logfile="<file>"
  Path to logfile.
sshkey="<file>"
  SSH key file used with ssh-client module.
show_modules="{yes|no}"
  Print the name of the included modules to standard output during build (default=no).
i18n_vars="<variable mapping>"
  Distribution specific variable mapping. See dracut/modules.d/10i18n/README for a detailed description.
i18n_default_font="<fontname>"
  The font <fontname> to install, if not specified otherwise. Default is "eurlatgr".
i18n_install_all="{yes|no}"
  Install everything regardless of generic or host-only mode (default=no).
reproducible="{yes|no}"
  Create reproducible images (default=no).
noimageifnotneeded="{yes|no}"
  Do not create an image in host-only mode, if no kernel driver is needed and no /etc/cmdline/*.conf will be generated into the initramfs (default=no).
loginstall="<directory>"
  Log all files installed from the host to <directory>.
uefi="{yes|no}"
  Instead of creating an initramfs image, dracut will create an UEFI executable, which can be executed by an UEFI BIOS (default=no). The default output filename is <EFI>/EFI/Linux/linux-$kernel$-<MACHINE_ID>-<BUILD_ID>.efi. <EFI> might be /efi, /boot or /boot/efi depending on where the ESP partition is mounted. The <BUILD_ID> is taken from BUILD_ID in /usr/lib/os-release or if it exists /etc/os-release and is left out, if BUILD_ID is non-existant or empty.
machine_id="{yes|no}"
  Affects the default output filename of the UEFI executable, including the <MACHINE_ID> part (default=yes).
uefi_stub="<file>"
  Specifies the UEFI stub loader, which will load the attached kernel, initramfs and kernel command line and boots the kernel. The default is /lib/systemd/boot/efi/linux<EFI-MACHINE-TYPE-NAME>.efi.stub.
uefi_splash_image="<file>"
  Specifies the UEFI stub loader’s splash image. Requires bitmap (.bmp) image format.
uefi_secureboot_cert="<file>", uefi_secureboot_key="<file>"
  Specifies a certificate and corresponding key, which are used to sign the created UEFI executable. Requires both certificate and key need to be specified and sbsign to be installed.
kernel_image="<file>"
  Specifies the kernel image, which to include in the UEFI executable. The default is /lib/modules/<KERNEL-VERSION>/vmlinuz or /boot/vmlinuz-<KERNEL-VERSION>.
enhanced_cpio="{yes|no}"
  Attempt to use the dracut-cpio binary, which optimizes archive creation for copy-on-write filesystems (default=no). When specified, initramfs archives are also padded to ensure optimal data alignment for extent sharing. To retain reflink data deduplication benefits, this should be used alongside the compress="cat" and do_strip="no" parameters, with initramfs source files, tmpdir staging area and destination all on the same copy-on-write capable filesystem.
parallel="{yes|no}"
  If set to yes, try to execute tasks in parallel (currently only supported for --regenerate-all).

## Files

/etc/dracut.conf
  Old configuration file. You better use your own file in /etc/dracut.conf.d/.
/etc/dracut.conf.d/
  Any /etc/dracut.conf.d/*.conf file can override the values in /etc/dracut.conf. The configuration files are read in alphanumerical order.

## AUTHOR

Harald Hoyer

## See Also

dracut(8) dracut.cmdline(7)

## Chapter 8. DRACUT.CMDLINE(7)

## 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 must 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 180 seconds. After 2/3 of the time, degraded raids are force started. If you have hardware, which takes a very long time to announce its drives, you might want to extend this value.
rd.timeout=<seconds>
  specify how long dracut should wait for devices to appear. The default is 0, which means forever. Note that this timeout should be longer than rd.retry to allow for proper configuration.
rd.noverifyssl
  accept self-signed certificates for ssl downloads.
rd.ctty=<terminal device>
  specify the controlling terminal for the console. This is useful, if you have multiple "console=" arguments.
rd.shutdown.timeout.umount=<seconds>
  specify how long dracut should wait for an individual umount to finish during shutdown. This avoids the system from blocking when unmounting a file system cannot complete and waits indefinitely. Value 0 means to wait forever. The default is 90 seconds.

### Debug

If you are dropped to an emergency shell, the file /run/initramfs/rdsosreport.txt is created, which can be saved to a (to be mounted by hand) partition (usually /boot) or a USB stick. Additional debugging info can be produced by adding rd.debug to the kernel command line. /run/initramfs/rdsosreport.txt contains all logs and the output of some tools. It should be attached to any report about dracut problems.

rd.info
  print informational output though "quiet" is set
rd.shell
  allow dropping to a shell, if root mounting fails
rd.debug
  set -x for the dracut shell. If systemd is active in the initramfs, all output is logged to the systemd journal, which you can inspect with "journalctl -ab". If systemd is not active, the logs are written to dmesg and /run/initramfs/init.log. If "quiet" is set, it also logs to the console.
rd.memdebug=[0-5]

  Print memory usage info at various points, set the verbose level from 0 to 5.

      Higher level means more debugging output:

          0 - no output
          1 - partial /proc/meminfo
          2 - /proc/meminfo
          3 - /proc/meminfo + /proc/slabinfo
          4 - /proc/meminfo + /proc/slabinfo + memstrack summary
              NOTE: memstrack is a memory tracing tool that tracks the total memory
                    consumption, and peak memory consumption of each kernel modules
                    and userspace progress during the whole initramfs runtime, report
                    is genereted and the end of initramsfs run.
          5 - /proc/meminfo + /proc/slabinfo + memstrack (with top memory stacktrace)
              NOTE: memstrack (with top memory stacktrace) will print top memory
                    allocation stack traces during the whole initramfs runtime.

rd.break
  drop to a shell at the end
rd.break={cmdline|pre-udev|pre-trigger|initqueue|pre-mount|mount|pre-pivot|cleanup}
  drop to a shell on defined breakpoint
rd.udev.info
  set udev to loglevel info
rd.udev.debug
  set udev to loglevel debug

### I18N

rd.vconsole.keymap=<keymap base file name>

  keyboard translation table loaded by loadkeys; taken from keymaps directory; will be written as KEYMAP to /etc/vconsole.conf in the initramfs.

  Example.

      rd.vconsole.keymap=de-latin1-nodeadkeys

rd.vconsole.keymap.ext=<list of keymap base file names>
  list of extra keymaps to bo loaded (sep. by space); will be written as EXT_KEYMAP to /etc/vconsole.conf in the initramfs
rd.vconsole.unicode
  boolean, indicating UTF-8 mode; will be written as UNICODE to /etc/vconsole.conf in the initramfs
rd.vconsole.font=<font base file name>

  console font; taken from consolefonts directory; will be written as FONT to /etc/vconsole.conf in the initramfs.

  Example.

      rd.vconsole.font=eurlatgr

rd.vconsole.font.map=<console map base file name>
  see description of -m parameter in setfont manual; taken from consoletrans directory; will be written as FONT_MAP to /etc/vconsole.conf in the initramfs
rd.vconsole.font.unimap=<unicode table base file name>
  see description of -u parameter in setfont manual; taken from unimaps directory; will be written as FONT_UNIMAP to /etc/vconsole.conf in the initramfs
rd.locale.LANG=<locale>

  taken from the environment; if no UNICODE is defined we set its value in basis of LANG value (whether it ends with ".utf8" (or similar) or not); will be written as LANG to /etc/locale.conf in the initramfs.

  Example.

      rd.locale.LANG=pl_PL.utf8

rd.locale.LC_ALL=<locale>
  taken from the environment; will be written as LC_ALL to /etc/locale.conf in the initramfs

### LVM

rd.lvm=0
  disable LVM detection
rd.lvm.vg=<volume group name>
  only activate all logical volumes in the the volume groups with the given name. rd.lvm.vg can be specified multiple times on the kernel command line.
rd.lvm.lv=<volume group name>/<logical volume name>
  only activate the logical volumes with the given name. rd.lvm.lv can be specified multiple times on the kernel command line.
rd.lvm.conf=0
  remove any /etc/lvm/lvm.conf, which may exist in the initramfs

### crypto LUKS

rd.luks=0
  disable crypto LUKS detection
rd.luks.uuid=<luks uuid>
  only activate the LUKS partitions with the given UUID. Any "luks-" of the LUKS UUID is removed before comparing to <luks uuid>. The comparisons also matches, if <luks uuid> is only the beginning of the LUKS UUID, so you don’t have to specify the full UUID. This parameter can be specified multiple times. <luks uuid> may be prefixed by the keyword `keysource:`, see rd.luks.key below.
rd.luks.allow-discards=<luks uuid>
  Allow using of discards (TRIM) requests for LUKS partitions with the given UUID. Any "luks-" of the LUKS UUID is removed before comparing to <luks uuid>. The comparisons also matches, if <luks uuid> is only the beginning of the LUKS UUID, so you don’t have to specify the full UUID. This parameter can be specified multiple times.
rd.luks.allow-discards
  Allow using of discards (TRIM) requests on all LUKS partitions.
rd.luks.crypttab=0
  do not check, if LUKS partition is in /etc/crypttab
rd.luks.timeout=<seconds>
  specify how long dracut should wait when waiting for the user to enter the password. This avoid blocking the boot if no password is entered. It does not apply to luks key. The default is 0, which means forever.

### crypto LUKS - key on removable device support

NB: If systemd is included in the dracut initrd, dracut’s built in removable device keying support won’t work. systemd will prompt for a password from the console even if you’ve supplied rd.luks.key. You may be able to use standard systemd fstab(5) syntax to get the same effect. If you do need rd.luks.key to work, you will have to exclude the "systemd" dracut module and any modules that depend on it. See dracut.conf(5) and https://bugzilla.redhat.com/show_bug.cgi?id=905683 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.

rd.luks.key.tout=0
  specify how many times dracut will try to read the keys specified in in rd.luk.key. This gives a chance to the removable device containing the key to initialise.

### MD RAID

rd.md=0
  disable MD RAID detection
rd.md.imsm=0
  disable MD RAID for imsm/isw raids, use DM RAID instead
rd.md.ddf=0
  disable MD RAID for SNIA ddf raids, use DM RAID instead
rd.md.conf=0
  ignore mdadm.conf included in initramfs
rd.md.waitclean=1
  wait for any resync, recovery, or reshape activity to finish before continuing
rd.md.uuid=<md raid uuid>
  only activate the raid sets with the given UUID. This parameter can be specified multiple times.

### DM RAID

rd.dm=0
  disable DM RAID detection
rd.dm.uuid=<dm raid uuid>
  only activate the raid sets with the given UUID. This parameter can be specified multiple times.

### MULTIPATH

rd.multipath=0
  disable multipath detection
rd.multipath=default
  use default multipath settings

### FIPS

rd.fips
  enable FIPS
boot=<boot device>

  specify the device, where /boot is located.

  Example.

      boot=/dev/sda1
      boot=/dev/disk/by-path/pci-0000:00:1f.1-scsi-0:0:1:0-part1
      boot=UUID=<uuid>
      boot=LABEL=<label>

rd.fips.skipkernel
  skip checksum check of the kernel image. Useful, if the kernel image is not in a separate boot partition.

### Network

### Important

It is recommended to either bind an interface to a MAC with the ifname argument, or to use the systemd-udevd predictable network interface names.

Predictable network interface device names based on:

- firmware/bios-provided index numbers for on-board devices
- firmware-provided pci-express hotplug slot index number
- physical/geographical location of the hardware
- the interface’s MAC address

See: http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames

Two character prefixes based on the type of interface:

en
  ethernet
wl
  wlan
ww
  wwan

Type of names:

o<index>
  on-board device index number
s<slot>[f<function>][d<dev_id>]
  hotplug slot index number
x<MAC>
  MAC address
[P<domain>]p<bus>s<slot>[f<function>][d<dev_id>]
  PCI geographical location
[P<domain>]p<bus>s<slot>[f<function>][u<port>][..][c<config>][i<interface>]
  USB port number chain

All multi-function PCI devices will carry the [f<function>] number in the device name, including the function 0 device.

When using PCI geography, The PCI domain is only prepended when it is not 0.

For USB devices the full chain of port numbers of hubs is composed. If the name gets longer than the maximum number of 15 characters, the name is not exported. The usual USB configuration == 1 and interface == 0 values are suppressed.

PCI ethernet card with firmware index "1"
  - eno1
PCI ethernet card in hotplug slot with firmware index number
  - ens1
PCI ethernet multi-function card with 2 ports
  - enp2s0f0
  - enp2s0f1
PCI wlan card
  - wlp3s0
USB built-in 3G modem
  - wwp0s29u1u4i6
USB Android phone
  - enp0s29u1u2

The following options are supported by the network-legacy dracut module. Other network modules might support a slightly different set of options; refer to the documentation of the specific network module in use. For NetworkManager, see nm-initrd-generator(8).

ip={dhcp|on|any|dhcp6|auto6|either6|link6|single-dhcp}
  dhcp|on|any
    get ip from dhcp server from all interfaces. If netroot=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
  link6
    bring up interface for IPv6 link-local addressing
ip=<interface>:{dhcp|on|any|dhcp6|auto6|link6}[:[<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
  link6
    bring up interface for IPv6 link local address
  <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}

  netroot=dhcp alone directs initrd to look at the DHCP root-path where NFS options can be specified.

  Example.

          root-path=<server-ip>:<root-dir>[,<nfs-options>]
          root-path=nfs:<server-ip>:<root-dir>[,<nfs-options>]
          root-path=nfs4:<server-ip>:<root-dir>[,<nfs-options>]

root=/dev/nfs nfsroot=[<server-ip>:]<root-dir>[:<nfs-options>]
  Deprecated! kernel Documentation_/filesystems/nfsroot.txt_ defines this method. This is supported by dracut, but not recommended.
rd.nfs.domain=<NFSv4 domain name>
  Set the NFSv4 domain name. Will override the settings in /etc/idmap.conf.
rd.net.dhcp.retry=<cnt>
  If this option is set, dracut will try to connect via dhcp <cnt> times before failing. Default is 1.
rd.net.timeout.dhcp=<arg>
  If this option is set, dhclient is called with "-timeout <arg>".
rd.net.timeout.iflink=<seconds>
  Wait <seconds> until link shows up. Default is 60 seconds.
rd.net.timeout.ifup=<seconds>
  Wait <seconds> until link has state "UP". Default is 20 seconds.
rd.net.timeout.route=<seconds>
  Wait <seconds> until route shows up. Default is 20 seconds.
rd.net.timeout.ipv6dad=<seconds>
  Wait <seconds> until IPv6 DAD is finished. Default is 50 seconds.
rd.net.timeout.ipv6auto=<seconds>
  Wait <seconds> until IPv6 automatic addresses are assigned. Default is 40 seconds.
rd.net.timeout.carrier=<seconds>
  Wait <seconds> until carrier is recognized. Default is 10 seconds.

### CIFS

root=cifs://[<username>[:<password>]@]<server-ip>:<root-dir>

  mount cifs share from <server-ip>:/<root-dir>, if no server-ip is given, use dhcp next_server. if server-ip is an IPv6 address it has to be put in brackets, e.g. [2001:DB8::1]. If a username or password are not specified as part of the root, then they must be passed on the command line through cifsuser/cifspass.

  ### Warning

  Passwords specified on the kernel command line are visible for all users via the file /proc/cmdline and via dmesg or can be sniffed on the network, when using DHCP with DHCP root-path.

cifsuser=<username>
  Set the cifs username, if not specified as part of the root.
cifspass=<password>

  Set the cifs password, if not specified as part of the root.

  ### Warning

  Passwords specified on the kernel command line are visible for all users via the file /proc/cmdline and via dmesg or can be sniffed on the network, when using DHCP with DHCP root-path.

### iSCSI

root=iscsi:[<username>:<password>[:<reverse>:<password>]@][<servername>]:[<protocol>]:[<port>][:[<iscsi_iface_name>]:[<netdev_name>]]:[<LUN>]:<targetname>

  protocol defaults to "6", LUN defaults to "0". If the "servername" field is provided by BOOTP or DHCP, then that field is used in conjunction with other associated fields to contact the boot server in the Boot stage. However, if the "servername" field is not provided, then the "targetname" field is then used in the Discovery Service stage in conjunction with other associated fields. See rfc4173.

  ### Warning

  Passwords specified on the kernel command line are visible for all users via the file /proc/cmdline and via dmesg or can be sniffed on the network, when using DHCP with DHCP root-path.

  Example.

      root=iscsi:192.168.50.1::::iqn.2009-06.dracut:target0

  If servername is an IPv6 address, it has to be put in brackets:

  Example.

      root=iscsi:[2001:DB8::1]::::iqn.2009-06.dracut:target0

root=??? netroot=iscsi:[<username>:<password>[:<reverse>:<password>]@][<servername>]:[<protocol>]:[<port>][:[<iscsi_iface_name>]:[<netdev_name>]]:[<LUN>]:<targetname> …

  multiple netroot options allow setting up multiple iscsi disks:

  Example.

      root=UUID=12424547
      netroot=iscsi:192.168.50.1::::iqn.2009-06.dracut:target0
      netroot=iscsi:192.168.50.1::::iqn.2009-06.dracut:target1

  If servername is an IPv6 address, it has to be put in brackets:

  Example.

      netroot=iscsi:[2001:DB8::1]::::iqn.2009-06.dracut:target0

  ### Warning

  Passwords specified on the kernel command line are visible for all users via the file /proc/cmdline and via dmesg or can be sniffed on the network, when using DHCP with DHCP root-path. You may want to use rd.iscsi.firmware.

root=??? rd.iscsi.initiator=<initiator> rd.iscsi.target.name=<target name> rd.iscsi.target.ip=<target ip> rd.iscsi.target.port=<target port> rd.iscsi.target.group=<target group> rd.iscsi.username=<username> rd.iscsi.password=<password> rd.iscsi.in.username=<in username> rd.iscsi.in.password=<in password>

  manually specify all iscsistart parameter (see `iscsistart --help`)

  ### Warning

  Passwords specified on the kernel command line are visible for all users via the file /proc/cmdline and via dmesg or can be sniffed on the network, when using DHCP with DHCP root-path. You may want to use rd.iscsi.firmware.

root=??? netroot=iscsi rd.iscsi.firmware=1
  will read the iscsi parameter from the BIOS firmware
rd.iscsi.login_retry_max=<num>
  maximum number of login retries
rd.iscsi.param=<param>

  <param> will be passed as "--param <param>" to iscsistart. This parameter can be specified multiple times.

  Example.

      "netroot=iscsi rd.iscsi.firmware=1 rd.iscsi.param=node.session.timeo.replacement_timeout=30"

  will result in

      iscsistart -b --param node.session.timeo.replacement_timeout=30

rd.iscsi.ibft rd.iscsi.ibft=1: Turn on iBFT autoconfiguration for the interfaces

rd.iscsi.mp rd.iscsi.mp=1: Configure all iBFT interfaces, not only used for booting (multipath)

rd.iscsi.waitnet=0: Turn off waiting for all interfaces to be up before trying to login to the iSCSI targets.

rd.iscsi.testroute=0: Turn off checking, if the route to the iSCSI target IP is possible before trying to login.

### FCoE

rd.fcoe=0
  disable FCoE and lldpad
fcoe=<edd|interface|MAC>:{dcb|nodcb}:{fabric|vn2vn}

  Try to connect to a FCoE SAN through the NIC specified by <interface> or <MAC> or EDD settings. The second argument specifies if DCB should be used. The optional third argument specifies whether fabric or VN2VN mode should be used. This parameter can be specified multiple times.

  ### Note

  letters in the MAC-address must be lowercase!

### NVMf

rd.nonvmf=0
  Disable 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=/dev/root netroot=dhcp with dhcp root-path=nbd:<server>:<port/exportname>[:<fstype>[:<mountopts>[:<nbdopts>]]]

  netroot=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".

### VIRTIOFS

root=virtiofs:<mount-tag>
  mount virtiofs share using the tag <mount-tag>. The tag name is arbitrary and must match the tag given in the qemu -device command.
rootfstype=virtiofs root=<mount-tag>
  mount virtiofs share using the tag <mount-tag>. The tag name is arbitrary and must match the tag given in the qemu -device command.

Both formats are supported by the virtiofs dracut module. See https://gitlab.com/virtio-fs/virtiofsd for more information.

Example.

    root=virtiofs:host rw

### 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 HMAC key path name>

  Set the path name of the EVM HMAC key.

  Example.

      evmkey=/etc/keys/evm-trusted.blob

evmx509=<EVM X.509 cert path name>

  Set the path name of the EVM X.509 certificate.

  Example.

      evmx509=/etc/keys/x509_evm.der

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)

## Chapter 9. LSINITRD(1)

## NAME

lsinitrd - tool to show the contents of an initramfs image

## SYNOPSIS

lsinitrd [OPTION…] [<image> [<filename> [<filename> […] ]]]

lsinitrd [OPTION…] -k <kernel version>

## DESCRIPTION

lsinitrd shows the contents of an initramfs image. if <image> is omitted, then lsinitrd uses the default image /efi/<machine-id>/<kernel-version>/initrd, /boot/<machine-id>/<kernel-version>/initrd, /boot/efi/<machine-id>/<kernel-version>/initrd, /lib/modules/<kernel-version>/initrd or /boot/initramfs-<kernel-version>.img.

## OPTIONS

-h, --help
  print a help message and exit.
-s, --size
  sort the contents of the initramfs by size.
-f, --file <filename>
  print the contents of <filename>.
-k, --kver <kernel version>
  inspect the initramfs of <kernel version>.
-m, --mod
  list dracut modules included of the initramfs image.
--unpack
  unpack the initramfs to the current directory, instead of displaying the contents. If optional filenames are given, will only unpack specified files, else the whole image will be unpacked. Won’t unpack anything from early cpio part.
--unpackearly
  unpack the early microcode initramfs to the current directory, instead of displaying the contents. Same as --unpack, but only unpack files from early cpio part.
-v, --verbose
  unpack verbosely

## AVAILABILITY

The lsinitrd command is part of the dracut package and is available from https://dracut.wiki.kernel.org

## AUTHORS

Harald Hoyer

Amerigo Wang

Nikoli

## SEE ALSO

dracut(8)

## Chapter 10. Developer Manual

## Chapter 11. DRACUT.MODULES(7)

## NAME

dracut.modules - dracut modules

## DESCRIPTION

dracut uses a modular system to build and extend the initramfs image. All modules are located in /usr/lib/dracut/modules.d or in <git-src>/modules.d. The most basic dracut module is 99base. In 99base the initial shell script init is defined, which gets run by the kernel after initramfs loading. Although you can replace init with your own version of 99base, this is not encouraged. Instead you should use, if possible, the hooks of dracut. All hooks, and the point of time in which they are executed, are described in the section called “Boot Process Stages”.

The main script, which creates the initramfs is dracut itself. It parses all arguments and sets up the directory, in which everything is installed. It then executes all check, install, installkernel scripts found in the modules, which are to be processed. After everything is installed, the install directory is archived and compressed to the final initramfs image. All helper functions used by check, install and installkernel are found in in the file dracut-functions. These shell functions are available to all module installer (install, installkernel) scripts, without the need to source dracut-functions.

A module can check the preconditions for install and installkernel with the check script. Also dependencies can be expressed with check. If a module passed check, install and installkernel will be called to install all of the necessary files for the module. To split between kernel and non-kernel parts of the installation, all kernel module related parts have to be in installkernel. All other files found in a module directory are module specific and mostly are hook scripts and udev rules.

## Boot Process Stages

dracut modules can insert custom script at various points, to control the boot process. These hooks are plain directories containing shell scripts ending with ".sh", which are sourced by init. Common used functions are in dracut-lib.sh, which can be sourced by any script.

### Hook: cmdline

The cmdline hook is a place to insert scripts to parse the kernel command line and prepare the later actions, like setting up udev rules and configuration files.

In this hook the most important environment variable is defined: root. The second one is rootok, which indicates, that a module claimed to be able to parse the root defined. So for example, root=iscsi:…. will be claimed by the iscsi dracut module, which then sets rootok.

### Hook: pre-udev

This hook is executed right after the cmdline hook and a check if root and rootok were set. Here modules can take action with the final root, and before udev has been run.

### Start Udev

Now udev is started and the logging for udev is setup.

### Hook: pre-trigger

In this hook, you can set udev environment variables with udevadm control --property=KEY=value or control the further execution of udev with udevadm.

### Trigger Udev

udev is triggered by calling udevadm trigger, which sends add events for all devices and subsystems.

### Main Loop

In the main loop of dracut loops until udev has settled and all scripts in initqueue/finished returned true. In this loop there are three hooks, where scripts can be inserted by calling /sbin/initqueue.

#### Initqueue

This hook gets executed every time a script is inserted here, regardless of the udev state.

#### Initqueue settled

This hook (initqueue/settled) gets executed every time udev has settled.

#### Initqueue timeout

This hook (initqueue/timeout) gets executed, when the main loop counter becomes half of the rd.retry counter.

#### Initqueue online

This hook (initqueue/online) gets executed whenever a network interface comes online (that is, once it is up and configured by the configured network module).

#### Initqueue finished

This hook (initqueue/finished) is called after udev has settled and if all scripts herein return 0 the main loop will be ended. Arbitrary scripts can be added here, to loop in the initqueue until something happens, which a dracut module wants to wait for.

### Hook: pre-mount

Before the root device is mounted all scripts in the hook pre-mount are executed. In some cases (e.g. NFS) the real root device is already mounted, though.

### Hook: mount

This hook is mainly to mount the real root device.

### Hook: pre-pivot

This hook is called before cleanup hook, This is a good place for actions other than cleanups which need to be called before pivot.

### Hook: cleanup

This hook is the last hook and is called before init finally switches root to the real root device. This is a good place to clean up and kill processes not needed anymore.

### Cleanup and switch_root

Init (or systemd) kills all udev processes, cleans up the environment, sets up the arguments for the real init process and finally calls switch_root. switch_root removes the whole filesystem hierarchy of the initramfs, chroot()s to the real root device and calls /sbin/init with the specified arguments.

To ensure all files in the initramfs hierarchy can be removed, all processes still running from the initramfs should not have any open file descriptors left.

## Network Infrastructure

FIXME

## Writing a Module

A simple example module is 90kernel-modules, which modprobes a kernel module after udev has settled and the basic device drivers have been loaded.

All module installation information is in the file module-setup.sh.

First we create a check() function, which just exits with 0 indicating that this module should be included by default.

check():

    return 0

Then we create the install() function, which installs a cmdline hook with priority number 20 called parse-insmodpost.sh. It also installs the insmodpost.sh script in /sbin.

install():

    inst_hook cmdline 20 "$moddir/parse-insmodpost.sh"
    inst_simple "$moddir/insmodpost.sh" /sbin/insmodpost.sh

The parse-instmodpost.sh parses the kernel command line for a argument rd.driver.post, blacklists the module from being autoloaded and installs the hook insmodpost.sh in the initqueue/settled.

parse-insmodpost.sh:

    for p in $(getargs rd.driver.post=); do
        echo "blacklist $p" >> /etc/modprobe.d/initramfsblacklist.conf
        _do_insmodpost=1
    done

    [ -n "$_do_insmodpost" ] && /sbin/initqueue --settled --unique --onetime /sbin/insmodpost.sh
    unset _do_insmodpost

insmodpost.sh, which is called in the initqueue/settled hook will just modprobe the kernel modules specified in all rd.driver.post kernel command line parameters. It runs after udev has settled and is only called once (--onetime).

insmodpost.sh:

    . /lib/dracut-lib.sh

    for p in $(getargs rd.driver.post=); do
        modprobe $p
    done

### module-setup.sh: check()

check() is called by dracut to evaluate the inclusion of a dracut module in the initramfs.

$hostonly
  If the $hostonly variable is set, then the module check() function should be in "hostonly" mode, which means, that the check() should only return 0, if the module is really needed to boot this specific host.

check() should return with:

0
  Include the dracut module in the initramfs.
1
  Do not include the dracut module. The requirements are not fulfilled (missing tools, etc.)
255
  Only include the dracut module, if another module requires it or if explicitly specified in the config file or on the argument list.

### module-setup.sh: depends()

The function depends() should echo all other dracut module names the module depends on.

### module-setup.sh: cmdline()

This function should print the kernel command line options needed to boot the current machine setup. It should start with a space and should not print a newline.

### module-setup.sh: install()

The install() function is called to install everything non-kernel related. To install binaries, scripts, and other files, you can use the functions mentioned in [creation].

To address a file in the current module directory, use the variable "$moddir".

### module-setup.sh: installkernel()

In installkernel() all kernel related files should be installed. You can use all of the functions mentioned in [creation] to install files.

### Creation Functions

#### inst_multiple [-o] <file> [ <file> …]

installs multiple binaries and files. If executables are specified without a path, dracut will search the path PATH=/usr/sbin:/sbin:/usr/bin:/bin for the binary. If the option "-o" is given as the first parameter, a missing file does not lead to an error.

#### inst <src> [<dst>]

installs one file <src> either to the same place in the initramfs or to an optional <dst>. inst with more than two arguments is treated the same as inst_multiple, all arguments are treated as files to install and none as install destinations.

#### inst_hook <hookdir> <prio> <src>

installs an executable/script <src> in the dracut hook <hookdir> with priority <prio>.

#### inst_rules <udevrule> [ <udevrule> …]

installs one or more udev rules. Non-existant udev rules are reported, but do not let dracut fail.

#### instmods <kernelmodule> [ <kernelmodule> … ]

instmods should be used only in the installkernel() function.

instmods installs one or more kernel modules in the initramfs. <kernelmodule> can also be a whole subsystem, if prefixed with a "=", like "=drivers/net/team".

instmods will not install the kernel module, if $hostonly is set and the kernel module is not currently needed by any /sys/…/uevent MODALIAS. To install a kernel module regardless of the hostonly mode use the form:

    hostonly='' instmods <kernelmodule>

### Initramfs Functions

FIXME

### Network Modules

FIXME

## AUTHOR

Harald Hoyer

## SEE ALSO

dracut(8)

## Chapter 12. DRACUT.BOOTUP(7)

## NAME

dracut.bootup - boot ordering in the initramfs

## DESCRIPTION

This flow chart illustrates the ordering of the services, if systemd is used in the dracut initramfs.

                                        systemd-journal.socket
                                                   |
                                                   v
                                        dracut-cmdline.service
                                                   |
                                                   v
                                        dracut-pre-udev.service
                                                   |
                                                   v
                                         systemd-udevd.service
                                                   |
                                                   v
    local-fs-pre.target                dracut-pre-trigger.service
             |                                     |
             v                                     v
     (various mounts)  (various swap  systemd-udev-trigger.service
             |           devices...)               |             (various low-level   (various low-level
             |               |                     |             services: seed,       API VFS mounts:
             v               v                     v             tmpfiles, random     mqueue, configfs,
      local-fs.target   swap.target     dracut-initqueue.service    sysctl, ...)        debugfs, ...)
             |               |                     |                    |                    |
             \_______________|____________________ | ___________________|____________________/
                                                  \|/
                                                   v
                                            sysinit.target
                                                   |
                                 _________________/|\___________________
                                /                  |                    \
                                |                  |                    |
                                v                  |                    v
                            (various               |              rescue.service
                           sockets...)             |                    |
                                |                  |                    v
                                v                  |              rescue.target
                         sockets.target            |
                                |                  |
                                \_________________ |                                 emergency.service
                                                  \|                                         |
                                                   v                                         v
                                             basic.target                             emergency.target
                                                   |
                            ______________________/|
                           /                       |
                           |                       v
                           |            dracut-pre-mount.service
                           |                       |
                           |                       v
                           |                  sysroot.mount
                           |                       |
                           |                       v
                           |             initrd-root-fs.target
               (custom initrd services)            |
                           |                       v
                           |             dracut-mount.service
                           |                       |
                           |                       v
                           |            initrd-parse-etc.service
                           |                       |
                           |                       v
                           |            (sysroot-usr.mount and
                           |             various mounts marked
                           |               with fstab option
                           |                x-initrd.mount)
                           |                       |
                           |                       v
                           |                initrd-fs.target
                           \______________________ |
                                                  \|
                                                   v
                                              initrd.target
                                                   |
                                                   v
                                        dracut-pre-pivot.service
                                                   |
                                                   v
                                         initrd-cleanup.service
                                              isolates to
                                        initrd-switch-root.target
                                                   |
                                                   v
                            ______________________/|
                           /                       |
                           |        initrd-udevadm-cleanup-db.service
                           |                       |
               (custom initrd services)            |
                           |                       |
                           \______________________ |
                                                  \|
                                                   v
                                       initrd-switch-root.target
                                                   |
                                                   v
                                       initrd-switch-root.service
                                                   |
                                                   v
                                              switch-root

## AUTHOR

Harald Hoyer

## SEE ALSO

dracut(8) bootup(7)

## Appendix A. License

This work is licensed under the Creative Commons Attribution/Share-Alike License. To view a copy of this license, visit http://creativecommons.org/licenses/by-sa/3.0/ or send a letter to Creative Commons, 559 Nathan Abbott Way, Stanford, California 94305, USA.