Installing Xen On An Ubuntu 8.04 (Hardy Heron) Server From The Ubuntu Repositories
Author: Falko Timme
This tutorial provides step-by-step instructions on how to install Xen on an Ubuntu Hardy Heron (Ubuntu 8.04) server system (i386). You can find all the software used here in the Ubuntu repositories, so no external files (apart from a fixed Ubuntu Xen kernel to enable networking for the virtual machines) or compilation are needed.
Xen lets you create guest operating systems (*nix operating systems like Linux and FreeBSD), so called "virtual machines" or domUs, under a host operating system (dom0). Using Xen you can separate your applications into different virtual machines that are totally independent from each other (e.g. a virtual machine for a mail server, a virtual machine for a high-traffic web site, another virtual machine that serves your customers' web sites, a virtual machine for DNS, etc.), but still use the same hardware. This saves money, and what is even more important, it's more secure. If the virtual machine of your DNS server gets hacked, it has no effect on your other virtual machines. Plus, you can move virtual machines from one Xen server to the next one.
I will use Ubuntu Hardy Heron (i386) for the host OS (dom0) and Ubuntu Hardy Heron and Ubuntu Gutsy Gibbon (7.10) for the guest operating systems (domU). Other Debian-based distributions that can be installed using xen-tools are Debian Etch, Debian Lenny, Debian Sid, and Debian Sarge, as well as Ubuntu Dapper Drake, Ubuntu Edgy Eft, and Ubuntu Feisty Fawn.
This howto is meant as a practical guide; it does not cover the theoretical backgrounds. They are treated in a lot of other documents in the web.
This document comes without warranty of any kind! I want to say that this is not the only way of setting up such a system. There are many ways of achieving this goal but this is the way I take. I do not issue any guarantee that this will work for you!
1 Install The Ubuntu Hardy Heron Host System (dom0)
You can install the host system (dom0) as shown in the chapters one to ten of this tutorial: http://www.howtoforge.com/perfect-server-ubuntu8.04-lts (of course, you don't have to do this if you already have an Ubuntu 8.04 host system that you want to use).
Make sure that you are logged in as root (type in
to become root), because we must run all the steps from this tutorial as root user. Also, if you want to use vi as your text editor (as suggested by this tutorial), you should run
apt-get install vim-full
The vim-full package makes sure that the vi text editor behaves as expected (without vim-full, you might experience some strange behaviour in the vi text editor).
It's a good idea to disable AppArmor:
update-rc.d -f apparmor remove
dom0's FQDN in this example will be server1.example.com. server1.example.com's IP address will be 192.168.0.100 in this tutorial, and the gateway I use is 192.168.0.1, so the virtual machines will have to use that one, too.
2 Install Xen
To install Xen and all needed dependencies, all we have to do is run the following command:
apt-get install ubuntu-xen-server
This will also install the xen-tools package which we use later on to create virtual machines.
The ubuntu-xen-server package installs the Ubuntu kernel 2.6.24-16-xen; unfortunately there's a nasty bug in this kernel which causes networking to not work for virtual machines (see https://bugs.launchpad.net/ubuntu/+source/xen-3.2/+bug/204010 and https://bugs.launchpad.net/ubuntu/+source/linux/+bug/218126). Fortunately Hirano Takahito has patched this kernel and made the patched versions (for i386 and amd64) available on http://www.il.is.s.u-tokyo.ac.jp/~hiranotaka/ (I have created a mirror of these packages at http://downloads.howtoforge.com/ubuntu_8.04_server_xen_from_repositories/ in case the original link doesn't work anymore one day). Download the correct linux-image package for your architecture (i386 or amd64), e.g.:
Then replace the Ubuntu 2.6.24-16-xen kernel with it like this:
dpkg -i linux-image-2.6.24-16-xen_2.6.24-16.30zng1_i386.deb
Next do this:
mv /lib/tls /lib/tls.disabled
We also need to add the loop module to the kernel every time we boot our system, so we edit /etc/modules. If you already have a loop line in there, make it look like this, otherwise add it:
[...] loop max_loop=64 [...]
Now take a look at the /boot directory to see which kernels and ramdisks are installed:
ls -l /boot/
root@server1:~# ls -l /boot/
-rw-r--r-- 1 root root 426444 2008-04-10 18:55 abi-2.6.24-16-server
-rw-r--r-- 1 root root 80203 2008-04-10 18:55 config-2.6.24-16-server
-rw-r--r-- 1 root root 85149 2008-04-19 23:17 config-2.6.24-16-xen
drwxr-xr-x 2 root root 4096 2008-05-06 15:19 grub
-rw-r--r-- 1 root root 7323503 2008-04-24 11:47 initrd.img-2.6.24-16-server
-rw-r--r-- 1 root root 7047843 2008-04-24 11:45 initrd.img-2.6.24-16-server.bak
-rw-r--r-- 1 root root 7056979 2008-05-06 15:19 initrd.img-2.6.24-16-xen
-rw-r--r-- 1 root root 7062168 2008-05-06 15:09 initrd.img-2.6.24-16-xen.bak
-rw-r--r-- 1 root root 103204 2007-09-28 12:06 memtest86+.bin
-rw-r--r-- 1 root root 933296 2008-04-10 18:55 System.map-2.6.24-16-server
-rw-r--r-- 1 root root 883544 2008-04-19 23:17 System.map-2.6.24-16-xen
-rw-r--r-- 1 root root 1987288 2008-04-10 18:55 vmlinuz-2.6.24-16-server
-rw-r--r-- 1 root root 1730344 2008-04-19 23:17 vmlinuz-2.6.24-16-xen
-rw-r--r-- 1 root root 370610 2008-04-11 03:16 xen-3.2.gz
The /boot/vmlinuz-2.6.24-16-xen kernel is the new, patched Xen kernel, and /boot/initrd.img-2.6.24-16-xen is its ramdisk. We will need these soon.
You can now also take a look at the /usr/lib/xen-tools directory because it reveals which distributions can be installed in a virtual machine with xen-tools:
ls -l /usr/lib/xen-tools
root@server1:~# ls -l /usr/lib/xen-tools
drwxr-xr-x 2 root root 4096 2008-05-06 15:08 centos-4.d
drwxr-xr-x 2 root root 4096 2008-05-06 15:08 centos-5.d
-rwxr-xr-x 1 root root 4409 2008-04-06 03:12 common.sh
drwxr-xr-x 2 root root 4096 2008-05-06 15:08 dapper.d
drwxr-xr-x 2 root root 4096 2008-05-06 15:08 debian.d
drwxr-xr-x 2 root root 4096 2008-05-06 15:08 edgy.d
lrwxrwxrwx 1 root root 8 2008-05-06 15:08 etch.d -> debian.d
lrwxrwxrwx 1 root root 15 2008-05-06 15:08 fedora-core-4.d -> fedora-core-6.d
lrwxrwxrwx 1 root root 15 2008-05-06 15:08 fedora-core-5.d -> fedora-core-6.d
drwxr-xr-x 2 root root 4096 2008-05-06 15:08 fedora-core-6.d
lrwxrwxrwx 1 root root 15 2008-05-06 15:08 fedora-core-7.d -> fedora-core-6.d
lrwxrwxrwx 1 root root 6 2008-05-06 15:08 feisty.d -> edgy.d
drwxr-xr-x 2 root root 4096 2008-05-06 15:08 gentoo.d
lrwxrwxrwx 1 root root 6 2008-05-06 15:08 gutsy.d -> edgy.d
lrwxrwxrwx 1 root root 6 2008-05-06 15:08 hardy.d -> edgy.d
lrwxrwxrwx 1 root root 8 2008-05-06 15:08 lenny.d -> debian.d
lrwxrwxrwx 1 root root 8 2008-05-06 15:08 sarge.d -> debian.d
lrwxrwxrwx 1 root root 8 2008-05-06 15:08 sid.d -> debian.d
As you see we can install the following distributions:
- Debian: Etch, Lenny (testing), Sid (unstable), Sarge
- Ubuntu: Dapper Drake, Edgy Eft, Feisty Fawn, Gutsy Gibbon, Hardy Heron
- CentOS 4, CentOS 5
- Fedora Core 4, 5, 6, Fedora 7
(I haven't tried to install CentOS, Fedora, and Gentoo with xen-tools yet, so I can't say how good it works.)
I want to store my virtual machines in the /home/xen directory, therefore I create it now:
We will use xen-tools to create virtual machines. xen-tools make it very easy to create virtual machines - please read this tutorial to learn more: http://www.howtoforge.com/xen_tools_xen_shell_argo. As mentioned before, the xen-tools package got installed together with the ubuntu-xen-server package.
Now we edit /etc/xen-tools/xen-tools.conf. This file contains the default values that are used by the xen-create-image script unless you specify other values on the command line. I changed the following values and left the rest untouched:
[...] dir = /home/xen [...] dist = hardy # Default distribution to install. [...] gateway = 192.168.0.1 netmask = 255.255.255.0 broadcast = 192.168.0.255 [...] passwd = 1 [...] mirror = http://archive.ubuntu.com/ubuntu/ [...]
The dist line holds the default distribution that you want to install in a virtual machine. The contents of the /usr/lib/xen-tools directory reveals which distributions are available (see above).
The kernel line must contain our Xen kernel, and the initrd line its ramdisk. The default /etc/xen-tools/xen-tools.conf file has the values kernel = /boot/vmlinuz-`uname -r` and initrd = /boot/initrd.img-`uname -r` which automatically translate to the correct kernel and ramdisk, so we don't have to modify these lines.
The passwd = 1 line makes that you can specify a root password when you create a new guest domain. In the mirror line specify an Ubuntu mirror close to you.
Make sure you specify a gateway and netmask. If you don't, and you don't specify a gateway and netmask on the command line when using xen-create-image, your guest domains won't have networking even if you specified an IP address!
Now reboot the system:
If your system reboots without problems, then everything is fine!
and your new Xen kernel should show up:
root@server1:~# uname -r