    <chapt id="initramfs">
      <heading>Managing the initial ramfs (initramfs) archive</heading>
      <p>
        The booting in Debian is a two-stage process, involving
	the initial RAM filesystem (initramfs for short, sometimes it
	is also referred to as initrd, which stands for initial RAM
	disk). First, the bootloader loads the kernel and initramfs
	into memory, and passes the execution control to the
	kernel. After basic initialization the kernel extracts the
	initramfs archive and mounts it as a temporary root
	filesystem. initramfs contains kernel modules and userspace
	programs required to initialize the physical or logical
	device(s) containing the real root filesystem. The
	<tt>init</tt> script on the initramfs loads modules and
	performs other neccessary initialization steps. At the end of
	this stage <tt>run-init</tt> deletes the initramfs from
	memory, mounts the real root filesystem and passes control to
	the <tt>/sbin/init</tt> program on it.
      </p>
      <p>
        Two major goals are achieved with such setup: the kernel size
	is kept under control by allowing most of the drivers to be
	compiled as modules (in a initramfs-less setup the drivers
	neccessary for the boot-time initialization of the root device
	must be compiled into it) and allow the setups which require
	initialization which cannot be done in-kernel, but is performed
	by userspace utilities.
      </p>
      <sect id="initramfs-gen-tools">
        <heading>Initramfs generation tools</heading>
      <p>
        Since initramfs usually needs to be customized for the particular
	hardware/device configuration and kernel version, they are not
	included as a part of any package, but are generated on the
	fly at kernel installation time. Currently there are two tools
	in Debian capable of generating an initramfs:
	<tt>update-initramfs</tt> provided by <tt>initramfs-tools</tt>
	(default) and <tt>dracut-update-initramfs</tt> provided by the
	<tt>dracut</tt> package (experimental).
      </p>
      </sect>
      <sect id="initramfs-regen">
        <heading>Regenerating the initramfs</heading>
      <p>
        If changes are desired after the corresponding
	<tt>linux-image</tt> has been installed, the initramfs needs to
	be regenerated. This is achieved by the command
	<example>
# dpkg-reconfigure linux-image-3.2.0-2-686-pae
        </example>
        where <tt>linux-image-3.2.0-2-686-pae</tt> is the name of the
	kernel package for which the initramfs regeneration is requested.
      </sect>
      <sect id="initramfs-exam">
        <heading>Examining the initramfs contents</heading>
	<p>
	Occasionally it is useful to examine the contents of initramfs
	to diagnose a problem or for educational purposes. They are
	compressed <tt>cpio</tt> archives, which may be extracted
	using the command
	<example>
$ zcat /boot/initrd.img-3.2.0-2-686-pae | cpio -i
        </example>
	It will unpack the contents of the initramfs into the current directory.
	</p>
	<p>
	  It is also possible to list the contents of an initramfs
	  using the <tt>cpio -t</tt> option or the command
	  <example>
$ lsinitramfs /boot/initrd.img-3.2.0-2-686-pae
          </example>
	</p>
      </sect>
    </chapt>
