Xen

https://wiki.debian.org/Xen

First install the hypervisor, xen aware kernel and xen tools. This can be done by a metapackage:

> apt-get install xen-linux-system

Debian Squeeze uses Grub 2 whose default is to list normal kernels first, and only then list the Xen hypervisor and its kernels.

You can change this to cause Grub to prefer to boot Xen by changing the priority of Grub's Xen configuration script (20_linux_xen) to be higher than the standard Linux config (10_linux). This is most easily done using dpkg-divert:

> dpkg-divert --divert /etc/grub.d/08_linux_xen --rename /etc/grub.d/20_linux_xen

to undo this:

> dpkg-divert --rename --remove /etc/grub.d/20_linux_xen

After any update to the Grub configuration you must apply the configuration by running:

update-grub

In order to give network access to guest domains it is necessary to configure the domain 0 network appropriately. The most common configuration is to use a software bridge.

It is recommended that you manage your own network bridge using the Debian network bridge. The Xen wiki page Host Configuration/Networking also has some useful information. The Xen supplied network scripts are not always reliable and will be removed from a later version. They are disabled by default in Debian's packages.

If you have a router that assigns ip addresses through dhcp, the following is a working example of the /etc/network/interfaces file using bridge-utils software.

> nano /etc/network/interfaces

#The loopback network interface
auto lo
iface lo inet loopback

iface eth0 inet manual

auto xenbr0
iface xenbr0 inet dhcp
   bridge_ports eth0

#other possibly useful options in a virtualized environment
  #bridge_stp off       # disable Spanning Tree Protocol
  #bridge_waitport 0    # no delay before a port becomes available
  #bridge_fd 0          # no forwarding delay

activate your changes like this:

> ifdown eth0
> killall dhclient
> ifup xenbr0
> brctl show

bridge name bridge id       STP enabled interfaces
br-lan      8000.xxxxxxxxxxxx   no      eth0

You should see your new IP address on ifconfig br-lan, and you should still be able to ping out (e.g. ping 8.8.8.8 / and resolve: ping google.com).

On a system which is dedicated to running Xen guests it is better to instead give dom0 some static amount of RAM and to disable ballooning, here 1024MB.

In order to do this you must first add the dom0_mem option to your hypervisor command line. This is done by editing /etc/default/grub and adding:

In order to do this you must first add the dom0_mem option to your hypervisor command line. This is done by editing /etc/default/grub and adding

# Xen boot parameters for all Xen boots
GRUB_CMDLINE_XEN="dom0_mem=1024M"

at the bottom of the file.

Remember to apply the change to the grub configuration by running

> update-grub

Then edit /etc/xen/xend-config.sxp to configure the toolstack to match by changing the following settings:

(dom0-min-mem 1024)
(enable-dom0-ballooning no)

At this point you should reboot so that these changes take effect.