Setting Up Guest Operating Systems

The output from xm list probably shows that domain 0 is taking up all the RAM on your system, which means there is no room to create a new guest OS. Fortunately, we can resize that memory usage downward to make space: Run the command xm mem-set Domain-0 256 to have domain 0 use 256MB RAM. This is the bare minimum for a Fedora install, so expect some slowdownif you have more than 512MB RAM, we recommend you allocate more to each VM.

Creating a domU VM on Fedora is handled with the xenguest-install.py script, which you should run as root. You are asked to do the following things:

• Give your virtual machine a friendly name (for example, FCUnleashed) so that you can differentiate between it and other virtual machines.

• Allocate it some RAM, with the minimum being 256MB; more is better.

• Choose where it should save its files. Xen uses a loopback filesystem so that all of a VM's files are stored in just one file on domain 0. Enter something like /home/paul/vms/fcu.img.

• Select how big the virtual disk should be. For a basic install, around 4.0GB should be enough.

• Set the install location (where Fedora should install from). This needs to be an online resource, so enter http://download.fedora.redhat.com/pub/fedora/linux/core/5/i386.

Now sit back and wait. Downloading the necessary files can take quite a while depending on your connection speed.

Anaconda eventually asks whether you want to install using text mode or VNCchoose Start VNC so that you have a graphical install. Xen's guests do not have direct access to the hardware, which means they have nowhere to display graphics. VNC lets you have your Xen VM render its graphics to your dom0 display inside a window, which means you can work with multiple VMs simultaneously. When you select Start VNC, you are prompted to enter a password. Click OK, and you see the VNC address you need to connect to. This address should look something like 10.0.0.1:1, where the :1 is the number of the VNC display.

Back on dom0, you should have installed VNC Viewer at the start of this chapter, so go to Applications, Accessories, VNC Viewer. Now enter that address (including the :1 or whatever it is for you) and click Connect. Enter your password when prompted. VNC starts and you see the Fedora installer. Depending on the resolution of your screen, the Fedora installer might not fit entirely on the screen; in that case, you have to use the scrollbars to get around.

The installer is as normal from here on in, except of course that it is using the virtual disk we created earlier so you have only a small amount of space. It might refer to your hard disk as something like /dev/xvdado not worry about that.