Moving from the concept of a Xen infrastrucutre to actually realizing its potential doesn't have to be a nightmare. In the first part of this series, you learned how to install Citrix XenServer 4.1.
Installing a Linux virtual machine on XenServer
Installing a Linux VM in XenServer is not like installing a Linux operating system (OS). This is mainly because you can't start the installation from a virtualized CD-ROM or DVD. XenServer offers three methods to install a Linux virtual machine:
- Use the minimal Debian version that is included with XenServer
- Install from an installation server on the network
- Enter the XenServer installation cd in the optical drive of a physical Linux server and use a physical-to-virtual (P2V) conversion to create a virtual machine that is based on the virtual machine.
In this example we'll cover installation from a network installation server perspective. This assumes that you have an installation server available on the network.
To start the installation of the Linux virtual machine, start XenCenter and log into XenServer. Make sure that you click on your server in XenCenter, otherwise you won't be able to do anything. You'll now see eight tabs on which you can get more information about your server (see figure 1).
Figure1. After clicking on your server in XenCenter, you will see configuration details about your server.
Now click the 'New VM' button. This starts a wizard that will create your virtual machine. From the list of available templates, select the OS that you want to install. If your operating system is not listed, select 'Other Operating System'.
Figure 2. Select the operating system you want to install from the list of templates.
Now enter a name and, if you prefer, a description for the virtual machine you are about to create and click 'Next' to continue. In the next window, you will need to enter some of the virtual machine details. You need a URL in HTTP, FTP or NFS that brings you to the installation repository on your installation server. You can also enter advanced boot parameters for your operating system. If you don't have special needs here, just leave the default settings.
Figure 3. To perform the installation, you need to enter a URL to the installation repository.
In the next window you can define the virtual hardware that the VM can use. XenServer allows you to define more virtual CPUs than the amount of physical cores available on your server. It is not a good idea to do this because it will result in very bad performance of your virtual machine. You will also need to enter the amount of memory that will be initially granted to the virtual machine. Don't agonize over the amount of memory as it is relatively easy to increase later.
Figure 4. Never give your virtual machines more virtual CPUs than the amount of physical CPUs in your server.
Next, define the size of the virtual disk file. The default values tend to be rather small, so consider increasing it. Also, select where you want to create the disk file. If you allocated all storage to the storage resource pool, you can only select 'Local Storage' on XenServer.
Figure 5. By default, the installer creates an 8GB disk file in the storage resource pool on your server.
Now accept the default settings for the network cards and click 'Next'. This gives you a summary screen where you can click 'Finish' to complete this part of the installation. The installation of the virtual machine will start automatically and you can monitor its performance in the XenCenter interface.
Figure 6. On the General tab, you can see how heavy the performance load of the virtual machine installation is for your server
To complete installation, activate the Console tab in XenCenter. This shows you the installation program waiting for input. From this point, complete the installation until your new virtual machine is fully available.
Now you know how to install a Linux virtual machine. Because you can't start the installation directly from CD-ROM or DVD, the best way of installing virtual Linux is by using a network installation server. In the next part of this series, you'll learn how to perform a physical-to-virtual conversion.
About the author: Sander van Vugt is an author and independent technical trainer, specializing in Linux since 1994. van Vugt is also a technical consultant for high availability (HA) clustering and performance optimization, as well as an expert on SUSE Linux Enterprise Desktop 10 (SLED 10) administration.
This was first published in July 2008