Fedora Linux

? The Fedora Core Installation Manual: http://fedora.redhat.com/docs/fedora-install-guide-en/fc6/

? The manpages for chroot , wget , scp , and lvm

10.7. Installing Xen Virtual Machines

Xen is a technology that permits one physical computer to act as two or more virtual machines (or domains ). Each domain is isolated from other domains, so administration privilege can be safely delegated; you can designate a system administrator for one domain and give him the root password for total control of that system, confident that he will not be able to touch the configuration of other domains.

Virtualization technology is also very helpful when testing multiple software versions or configurations, and since virtual machines can be migrated between physical systems, it provides a lot of flexibility for server deployment and management.

To use Xen, you must install a special kernel and utilities on your existing Fedora system, which then becomes your primary domain ( Domain-0 ). You can then install Fedora on as many additional domains as you want.

10.7.1. How Do I Do That?

To set up for Xen, install the kernel-xen and xen packages using Pirut or this command :

# yum -y install kernel-xen xen

Reboot your system. When the GRUB boot screen appears, press the spacebar to display the boot menu. Select the new xen kernel using the cursor keys, and then press Enter to boot.

To make your system boot the Xen kernel by default, edit /boot/grub/grub.conf (see Lab 10.5, 'Configuring the GRUB Bootloader') 

You can confirm that you are running the Xen kernel by using the uname command:

# uname -r
2.6.17-1.2564.fc6xen

The xend service should also be running, which you can confirm using the service command:

# service xend status
service xend is running

The Fedora installation that you are using is Domain-0 , the master domain. Additional virtual machines, called guest domains , must be installed from a network installation server. If you do not have one, you can quickly set up one within Domain-0 by inserting a Fedora Core DVD and typing:

# yum -y install httpd
...(Lines snipped)...
# setenforce 0
# ln -s /media/ disk /var/www/html/fedora
# service httpd start
Starting httpd: [ OK ]

The setenforce command just shown disables SELinux protection for your system, which presents a security risk. Re-enable SELinux as soon as you are finished using the network installation server:

# setenforce 1

To start the guest domain installation:

# xenguest-install
What is the name of your virtual machine? fedora
How much RAM should be allocated (in megabytes)? 256
What would you like to use as the disk (path)? /var/xen/fedora
How large would you like the disk to be (in gigabytes)? 2
Would you like to enable graphics support (yes or no) no
What is the install location? http://192.168.2.48/fedora

The name of the virtual machine can be any value that meets the requirements for a filename. The disk path and size requested are used to set up a file that will act as the hard disk for the guest domain. The install location is the URL of the network installation server; if you're using an HTTP server on Domain- 0 , use the full IP address of that system instead of the loopback address 127.0.0.1 (since, inside a guest domain, the loopback destination is the guest domain itself, not Domain-0 ).

A regular Fedora installation will now start in text mode within the guest domain. After prompting you for the language and keyboard, the installer will give you the option of continuing with a text mode installation or using VNC for a graphical installation, as shown in Figure 10-29 .

Figure 10-29. Text mode and VNC installation options    

This message indicates that the installer was unable to start X. This is normal, since the guest domain does not have a video card.

Choose one of the two options:

? To continue in text mode, press Enter.

? To use VNC, press Tab, and then press Enter. The installer will prompt you to create a VNC password and will then start a VNC server. This message will be displayed on the screen:

? Starting VNC...
? The VNC server is now running.
? Please connect to 192.168.2.112:1 to begin the install...
? Starting graphical installation...