MKINITRD(8)

NAME
mkinitrd - create or rebuilt an initrd (initial ramdisk).

SYNOPSIS
mkinitrd [ -c ] [ -f filesystem ] [ -k kernel_version ] [ -m module1:module2:module3... ] [ -o output_file ] [ -r root_device ] [ -s source_tree ]

DESCRIPTION
mkinitrd is used to build an initial ramdisk. An initial ramdisk is a very small Linux filesystem that is loaded into RAM and mounted 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

-c  Clear the existing initrd tree (by default in /boot/initrd-tree/) first.

-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.

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

-m module list
    This is a list of colon-delimited modules to build into the initrd. For example, the modules needed for the ext3 filesystem would be: jbd:ext3

-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. will be used). The default is "tagfile" in the package's directory.

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

-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 2.6.7 kernel modules for a system with an ext3 root partition on /dev/hdb3:
  mkinitrd -c -k 2.6.7 -m jbd: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-2.6.7
   initrd = /boot/initrd.gz
   root = /dev/hda6
   label = Linux267
   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!

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