====== Setting up a Xen Host System ======

While many different Linux distributions include packages for Xen, this page focuses on CentOS 5 and Redhat Enterprise 5, which we have found to be well supported and easy to setup. To make full use of Xen, you should be running one of these distributions on a machine with plenty of RAM (2 GB or more), enough disk space for all the filesystems of instances you want to host, and a CPU that supports either Intel's VTI extensions or AMD Pacifica.

===== CentOS 5 =====

Once you have a freshly installed system running CentOS 5, the steps to set it up for Xen hosting are :

  - Login as ''root'' via SSH or at the console.
  - Install the Xen kernel with the command <code>yum install kernel-xen kernel-xen-devel</code>
  - Once the new kernel has been installed, an entry for it will be automatically added to ''/boot/grub/menu.lst'' like : <code>title CentOS (2.6.18-8.1.4.el5xen)
        root (hd0,2)
        kernel /xen.gz-2.6.18-8.1.4.el5
        module /vmlinuz-2.6.18-8.1.4.el5xen ro root=/dev/VolGroup00/LogVol00 rhgb quiet
        module /initrd-2.6.18-8.1.4.el5xen.img</code>
  - Edit ''/boot/grub/menu.lst'' and change the ''default='' line to use the newly added Xen kernel, which will typically be the first one in the file (numbered 0).
  - Install the Xen commands package with the command <code>yum install xen</code>
  - Reboot the system with the ''reboot'' command. If you are at the console, you should be able to see Xen-related messages during the kernel boot process.
  - Verify that Xen is working with the command : <code>xm list</code> If you see a line starting with ''Domain-0'', then all is good.
  - Create the ''/xen'' directory, which VM2 uses by default for Xen system images, with the command <code>mkdir /xen</code>

And that's it! You can now register this system as a Xen host in VM2.

===== Redhat Enterprise 5 =====

If your RHEL 5 system has the ''yum'' command installed and working, you can follow the exact same steps above. If not, use Redhat's ''up2date'' command instead :

  - Login as ''root'' via SSH or at the console.
  - Make sure all packages are up to date and your Redhat Enterprise subscription is working by running the command : <code>up2date -u</code>
  - Install the Xen kernel with the command <code>up2date kernel-xen kernel-xen-devel</code>
  - Once the new kernel has been installed, an entry for it will be automatically added to ''/boot/grub/menu.lst'' like : <code>title Redhat Enterprise (2.6.18-8.1.4.el5xen)
        root (hd0,2)
        kernel /xen.gz-2.6.18-8.1.4.el5
        module /vmlinuz-2.6.18-8.1.4.el5xen ro root=/dev/VolGroup00/LogVol00 rhgb quiet
        module /initrd-2.6.18-8.1.4.el5xen.img</code>
  - Edit ''/boot/grub/menu.lst'' and change the ''default='' line to use the newly added Xen kernel, which will typically be the first one in the file (numbered 0).
  - Install the Xen commands package with the command <code>up2date xen</code>
  - Reboot the system with the ''reboot'' command. If you are at the console, you should be able to see Xen-related messages during the kernel boot process.
  - Verify that Xen is working with the command : <code>xm list</code> If you see a line starting with ''Domain-0'', then all is good.
  - Create the ''/xen'' directory, which VM2 uses by default for Xen system images, with the command <code>mkdir /xen</code>