This is part of my [xen box setup]{rtag/xen-box-setup} “series”.

Xen domain 0 (or dom0) is special. It starts up all the other xen hosts and, be it by a rule or simply by convention, it tends to run all the drivers.

I have already covered how I [partitioned my disk]{lvm2-on-raid1}. Let’s now start with this fresh install of debian/testing and get a xen dom0 running on top of it. The following steps assume that the system:

  • is a 32bit x86 box running debian/testing
  • has RAID1 devices configured as per my [LVM2 on RAID1]{lvm2-on-raid1} writeup
  • uses grub for a bootloader
  • was booting a recent 2.6.x kernel

Anyway, here goes…

  1. You will need to get some packages before we begin

     $ apt-get install xen-tools ssh python python2.3-twisted iproute bridge-utils libcurl3-dev \
   libncurses5-dev debootstrap zlib1g-dev make gcc build-essential python python-dev \
   python-twisted bzip2 module-init-tools tetex-base transfig tgif python-pyopenssl \
   python-pam python-serial netpbm vim initrd-tools

    I am no longer sure which are absolutely required and for what part of the xen build. Some were listed in the documentation, and others in various howto’s I’ve read.

    xen-tools is just a package with scripts and support files (like tab completion), etc. It can be skipped if you don’t want it.

  2. You will need to get xen

    The easiest way to get xen is to fetch it via bittorrent. Goto the xen download page and follow the instructions. You want to get the most recent release. At the time of this writing it was xen-3.0.1-install-x86_32.tgz.torrent.

    If you’re lazy, run…

     $ apt-get install bittorrent
 $ btdownloadheadless --spew 1 --url \
   http://tx.downloads.xensource.com/torrents/xen-3.0.1-install-x86_32.tgz.torrent

    This contains the binaries for 32bit x86 host. That includes:

    • xen kernel
    • linux kernel for dom0
    • linux kernel for domU (any other domain)
    • tools & script
    • sample configuration files
    • documentation

  3. Installing xen software

    Installation is relatively easy:

     $ tar xzf xen-3.0.1-install-x86_32.tgz.torrent
 $ cd xen-3.0.1-install
 $ less README

    (or at least come back here when things don’t work)

     $ ./install.sh

    The last step will build up an initrd image for the linux kernel to use to boot of raided SATA drives:

     $ depmod -a 2.6.12.6-xen0
 $ mkinitrd -o /boot/initrd.img-2.6.12.6-xen0 2.6.12.6-xen0
 $ depmod -a 2.6.12.6-xenU
 $ mkinitrd -o /boot/initrd.img-2.6.12.6-xenU 2.6.12.6-xenU

  4. Make xen bootable

    Before xen, you would tell grub to boot your vmlinuz file from /boot. Now grub will boot xen, and xen will boot your dom0 linux kernel. dom0 will then start up your domU domains.

    The first step is to get xen booting. Edit your /boot/grub/menu.lst file and just before the ### BEGIN AUTOMAGIC KERNELS LIST line insert a block that looks like this:

     title Xen 3.0 / XenLinux 2.6
 root   (hd0,0)
 kernel /boot/xen-3.0.gz console=vga
 module /boot/vmlinuz-2.6.12.6-xen root=/dev/md0 ro console=tty0
 module /boot/initrd.img-2.6.12.6-xen
 savedefault
 boot

    Note that the xen kernel will boot using the kernel directive, while the dom0 kernel will boot from the module directive.

After this you can reboot and your system should magically boot into…

$ uname -a
Linux phosphorus 2.6.12.6-xen #1 SMP Tue Jan 31 15:57:47 GMT 2006 i686 GNU/Linux

There will be more in the next installment.