MKINITRD(8)

NAME
mkinitrd - create or rebuilt an initrd (initial ramdisk) using initramfs (simple cpio+gzip).

SYNOPSIS
mkinitrd [ -F ] [ -c ] [ -f filesystem ] [ -h hibernate_partition ] [ -k kernel_version ] [ -m module1:module2:module3... ] [ -o output_file ] [ -r root_device ] [ -s source_tree ] [ -C crypt_device ] [ -L ] [ -R ] [ -V ]

DESCRIPTION
mkinitrd is used to build an initial ramdisk. An initial ramdisk is a very small set of files that are loaded into RAM and "mounted" (as initramfs doesn't actually use a filesystem) as the kernel boots (before the main root filesystem is mounted). The usual reason to use an initrd is because you need to load kernel modules before mounting the root partition. Usually these modules are required to support the filesystem used by the root partition (ext3, reiserfs, xfs), or perhaps the controller that the hard drive is attached to (SCSI, RAID, etc). Essentially, there are so many different options available in modern Linux kernels that it isn't practical to try to ship many different kernels to try to cover everyone's needs. It's a lot more flexible to ship a generic kernel and a set of kernel modules for it.

OPTIONS

-F  Use the contents of /etc/mkinitrd.conf as options to mkinitrd (optional). If this is used in conjunction with any other options passed on the command line, the command-line options will override the config file options.
    See mkinitrd.conf(5) for details.

-c  Clear the existing initrd tree (by default in /boot/initrd-tree/) first. If this is not done, running mkinitrd will add additional modules to the existing initrd.

-f filesystem
    Specify the filesystem to use for the root partition. If this isn't given, mount will usually figure it out. This option must be used together with the -r option in order to be beneficial.

--help
    Display a help summary.

-h hibernate_partition
    Specify the swap partition holding the hibernation image.

-k kernel version
    Use kernel modules from the specified kernel version. mkinitrd will look for them in /lib/modules/(kernel version).

-l keymap
    Load an alternative keyboard mapping. All supported keyboard mappings can be found in /usr/share/mkinitrd/keymaps.tar.gz Leave the '.bmap' out when you supply this parameter. E.g. '-l nl' will add support for dutch keyboard mapping to the initrd.

-m module list
    This is a list of colon-delimited modules to build into the initrd. Any dependencies of requested modules will also be added to the initrd. Additional options may be added to use when loading the kernel modules (but in this case the entire list must be wrapped with double quotes).

-o output image
    The file to write the initrd to. (default: /boot/initrd.gz)

-r root partition
    Specify the device to be used as the root partition. If this isn't given, the kernel default will be used (which is usually fine). This option must be used together with the -f option in order to be beneficial.

-s source tree
    The directory to use as the source for the initrd. (default: /boot/initrd-tree/)

-w  The -w option specifies how long to wait in seconds before assuming that all the drives are spun up and ready to go.

-C  Use cryptsetup to enable the underlying device of an encrypted root partition. Requires '-r' parameter. Two scenarios are possible.
    (1) root filesystem was created on the encrypted disk/LVM partition, example:
      -C /dev/sda2 -r cryptroot where /dev/sda2 is the encrypted partition and the actual root device name in /etc/fstab is:
      /dev/mapper/cryptroot (2) the encrypted partition contains a LVM volume which holds the root filesystem, example:
      -C /dev/sda2 -r /dev/vg/root where /dev/sda2 is the encrypted partition and the actual root device name in /etc/fstab is:
      /dev/vg/root

-L  This option adds LVM support to the initrd, if the tools are available on the system.

-R  This option adds RAID support to the initrd, if a static mdadm binary is available on the system.

-V  Display version information and exit.

EXAMPLES
A simple example: Build an initrd for a reiserfs root partition:
  mkinitrd -c -m reiserfs Another example: Build an initrd image using Linux 2.6.24.5 kernel modules for a system with an ext3 root partition on /dev/hdb3:
  mkinitrd -c -k 2.6.24.5 -m ext3 -f ext3 -r /dev/hdb3 If run without options, mkinitrd will rebuild an initrd image using the contents of the $SOURCE_TREE directory, or, if that directory does not exist it will be created and populated, and then mkinitrd will exit. These options are handy for building an initrd mostly by hand. After creating /boot/initrd-tree/, you can add modules and edit files by hand, and then rerun mkinitrd to create the initrd. Once the initrd is created, you'll need to tell your boot loader to load it. If you boot with LILO, you will need to add an initrd line to /etc/lilo.conf. Here's a section of lilo.conf that shows how to set this up:
 # Linux bootable partition config begins
 image = /boot/vmlinuz-generic-2.6.24.5
   initrd = /boot/initrd.gz
   root = /dev/hda6
   label = Linux26245
   read-only
 # Linux bootable partition config ends Once you've created the initrd and editing /etc/lilo.conf, you will need to run 'lilo' to write out the changed boot block. The next time you reboot the initrd should be loaded along with the kernel. Have fun!

SEE ALSO
mkinitrd.conf (5)

AUTHOR
Patrick J. Volkerding <volkerdi@slackware.com>