The installation procedure of Xen involves the setup of a domain-0 domain and the installation of Xen clients. First, make sure that the needed packages are installed. These are python, bridge-utils, xen, and a kernel-xen package. When using SUSE packages, Xen is added to the GRUB configuration. For other cases, make an entry in boot/grub/menu.lst. This entry should be similar to the following:
title Xen2
kernel (hd0,0)/boot/xen.gz dom0_mem=458752
module (hd0,0)/boot/vmlinuz-xen <parameters>
module (hd0,0)/boot/initrd-xen
Replace (hd0,0) with the partition that holds your /boot directory. See also Section 29.0, The Boot Loader. Alter the amount of dom0_mem to match your system. The maximum value is your system memory in kB minus 65536. Replace <parameters> with the parameters normally used to boot a Linux kernel. Then reboot into Xen mode. This boots the Xen hypervisor and a slightly changed Linux kernel as Domain-0 that runs most of the hardware. Apart from the exceptions already mentioned, everything should work as normal.