root@host:~# cat /etc/network/interfaces 
### Hetzner Online AG - installimage
# Loopback device:
auto lo
iface lo inet loopback
 
# device: eth0
auto eth0
iface eth0 inet static
  address 213.x.x.6
  broadcast 213.x.x.31
  netmask 255.255.255.224
  gateway 213.x.x.1
 
# default route to access subnet
up route add -net 213.x.x.0 netmask 255.255.255.224 gw 213.x.x.1 eth0
 
auto eth0:1
iface eth0:1 inet static
  address 78.x.x.1
  broadcast 78.x.x.7
  netmask 255.255.255.248

The plan is that the guests will get 78.x.x.2, 78.x.x.3, etc. and will use 78.x.x.1 as gateway (you’ll see this later) – that’s why I’ve assigned it to the host.

Well, after you have found out that Xen kernel is loaded with

uname -r
xm list

you’ll be ready to proceed.

Now we want to make a domU with Ubuntu Server 8.04 with the program debootstrap. First identify the partitions you want to use. For the root filesystem I’ll use /dev/lvmstore/lv1 and for swap I’ll use /dev/sda6. To prepare the partitions, please

mkfs.xfs /dev/lvmstore/lv1
mkswap /dev/sda6

Now it’s time to install the guest system. First mount the root file system like this:

mount /dev/lvmstore/lv1 /mnt

Now just install it with this simple command (depending on your environment you might have to change the --arch-parameter):

debootstrap --arch amd64 hardy /mnt http://archive.ubuntu.com/ubuntu

Now you should copy a couple of files:

cp /etc/resolv.conf /mnt/etc/resolv.conf
cp /etc/apt/sources.list /mnt/etc/apt/sources.list
mkdir /mnt/lib/modules/`uname -r`
cp -R /lib/modules/`uname -r`/* /mnt/lib/modules/`uname -r`/

Now you should change a couple of files. Now

vi /mnt/etc/network/interfaces

should have the content

root@host:~# cat /mnt/etc/network/interfaces 
auto lo
iface lo inet loopback
 
auto eth0
iface eth0 inet static
  address 78.x.x.2
  broadcast 78.x.x.7
  netmask 255.255.255.248
  gateway 78.x.x.1

Here you see that I’m using the host as gateway.

And

vi /mnt/etc/hostname

to change the hostname of the guest.

We also need to change the fstab – mine looks like this (remember to change xfs to ext3 or similar if you’re not using xfs):

root@host:~# cat /mnt/etc/fstab 
/dev/sda1 /    xfs  defaults 1 2
/dev/sda2 none swap sw       0 0

The names /dev/sda1 and /dev/sda2 is assigned on a Xen configuration file we’ll get to that i a minute.

Now we prepare the network bridge at the host by:

vi /etc/sysctl.conf

and change

#net.ipv4.ip_forward=1

to

net.ipv4.ip_forward=1

We also start the network bridge:

/etc/xen/scripts/network-bridge start

Now reboot the host to enable the changes in /etc/sysctl.conf. After reboot please check that the bridge is okay:

brctl show

Now we create the file /etc/xen/domU1.conf with this content:

root@host:~# cat /etc/xen/domu1.cfg 
kernel      = '/boot/vmlinuz-2.6.24-19-xen'
ramdisk     = '/boot/initrd.img-2.6.24-19-xen'
memory      = '512'
maxmem      = '1536'
 
root        = '/dev/sda1 ro'
disk        = ['phy:/dev/lvmstore/lv1,sda1,w','phy:/dev/sda6,sda2,w']
 
name        = 'domU1'
 
vif	     = ['bridge=eth0']
 
on_poweroff = 'destroy'
on_reboot   = 'restart'
on_crash    = 'restart'
 
vcpus	     = '2'
extra       = 'xencons=tty1'

This is the specs of the guest. This is a configuration making you able to ballon the amount of memory to 1,5 GB instead of the initial 512 MB. Please view man xmdomain.cfg for further details.

Now start the guest (the -c means that the console is attached to the guest immediately):

xm create /etc/xen/domu1.cfg -c

When the environment is started, login with the same password as on your host. Now check the network is okay, change the password, and update the system, respectively:

ping 78.x.x.1
passwd
apt-get update
apt-get upgrade
apt-get dist-upgrade

You’ll probably see some locales errors. For my case (da_DK) it’s fixed by this:

locale-gen da_DK.UTF8
tzselect
echo "export LANG=C" >> ~/.bashrc

Please refer to https://wiki.ubuntu.com/DebootstrapChroot for details regarding this and debootstrap in general.

To shut it down, use

init 0

You can start the guest without the -c-parameter to start it without the console. Then you can use

xm list

to check that it’s running.

At this point I’d strongly recommend to shut the guest down, reboot the host (dom0) and start everything again. This is to verify that everything is also working after a reboot (before using it in production).

I followed http://www.howtoforge.com/high-performance-xen-on-ubuntu-8.04-amd64 when I installed the guest, but I’ve done it slightly different and avoided some of the errors.