As some people have noticed, Xen is now available from the Fedora development repository. More information on Xen itself can be found at http://www.cl.cam.ac.uk/Research/SRG/netos/xen/index.html. We're following the -unstable Xen tree at the moment which does occasionally lead to things being broken but also lets us track a lot of the more interesting work going on there. Since setting up to run Xen isn't entirely straight-forward, here's a run-through of what should work for setting up a single Xen guest running the Fedora development tree. To run xen on a system pulling strictly from the Fedora devel repository, all of your deps should get satisfied automatically. But, they are explicitly * mkinitrd 4.2.0 * python 2.4 * python-twisted * Using grub as your boot loader [1] * Probably something on the order of 256 MB of RAM with the default setup [2] Then, you should be able to install the xen and kernel-xen0 packages. Once this is done, you should have an entry set up in your grub.conf to boot the xen0 kernel. Now, reboot into your new xen0 kernel [3] Once you've rebooted, you should be running in the dom0 kernel. You'll see a slightly scary looking warning about TLS during bootup and how to disable it, but it shouldn't make things too bad. Then, if you start xend with 'service xend start', you should be able to run 'xm list' and see your domain running. Now, we want to set up a simple base Fedora system. First, you'll want to install the kernel-xenU package (unfortunately, the kernel for your guest domain must currently be kept outside of the guest itself). Next, let's create a file to use as the backing for our Fedora install. For example purposes, I'll create one of a size of 1 GB. dd if=/dev/zero of=/root/fedora.img bs=1M count=1024 Now, create an ext3 filesystem on this image. mke2fs -F -j /root/fedora.img You should now be able to mount your new temporary rootfs on a temporary mountpoint, say /mnt mount -o loop /root/fedora.img /mnt Now, we can install whatever basesystem we want into this chroot. Make sure that your yum configuration points to a valid repository. Then, decide what group(s) you want to install. I'd recommend starting with Base (or for the space constrained, Core, but this is more difficult). Then, run yum --installroot=/mnt -y groupinstall Base Now, go get some coffee and have a snack. It's going to take a little while :-) Come back and if everything went okay, you'll have a minimal install in /mnt. Now, for the ugly part, we need to set up some basic bits on the filesystem that have to be different for xen right now. These include a) creating some required device nodes in /dev since we're not using an initrd and b) setting up an /etc/fstab for i in console null zero ; do MAKEDEV -d /mnt -x $i ; done For the /etc/fstab, something simple like the following should work /dev/sda1 / ext3 defaults 1 1 none /dev/pts devpts gid=5,mode=620 0 0 none /dev/shm tmpfs defaults 0 0 none /proc proc defaults 0 0 none /sys sysfs defaults 0 0 Do any other configuration you want to on the filesystem and then unmount it [4] umount /mnt{/proc,} Now, we just have to create a config file and you should be good to go. I go for a very simple config file like the following which is /etc/xen/rawhide on my machine [5] kernel ="/boot/vmlinuz-2.6.10-1.1103_FC4xenU" memory = 64 name = "rawhide" nics = 1 disk = ['file:/root/fedora.img,sda1,w'] root = "/dev/sda1 ro" Now, create a new domain with 'xm create -c rawhide' and off it goes. At the end, you should see the login prompt at which point you can login as root and begin playing around some. This is pretty early and rough, but it's enough to starting playing with. The next step (for me :) is getting to where you can do actual installs in a Xen guest environment and then being able to boot kernels which are on the guest's filesystem. Jeremy [1] This is required because you actually boot the Xen hypervisor and it then starts the Linux kernel. It does this using the MultiBoot standard [2] You can conceivably get by with less, but you'll have to reduce the dom0_memory line in /boot/grub/grub.conf. The 130000 for dom0 is currently hard-coded by mkinitrd (will get fixed before too long) and can go a little lower. Also, the Xen hypervisor ends up requiring ~ 32 MB. Plus any memory for your unprivileged guests. [3] Note, you may need to disable rhgb and switch to using runlevel 3. There are conflicting reports about X working; I haven't tried [4] And /proc under it, since /proc has to get mounted for a lot of things to get done right. But yum figures that out [5] Substitute /boot/vmlinuz-2.6.10-1.1090_FC4xenU with the xenU kernel you installed. Additionally, the device sda1 listed here as the disk is related to the /etc/fstab you created above
