Howto create CentOS Xen VM under Ubuntu Dom0

Posted Wed, 02/25/2009 - 16:21 by ma

In this article, I will show you how to create CentOS 5.2 virtual machines under a Ubuntu 8.04 server LTS dom0 (Xen 3.2).

First you need to create some directories : 

mkdir /home/xen/domains/centos
mkdir /mnt/img
mkdir /mnt/vm1

Next get the image from jailtime.org.

AMD64

i386

Put the file in /home/xen/domains/centos and uncompress it (from here I will use the AMD64 file) : 

cd /home/xen/domains/centos/
tar -xjf centos.5-2.64.20080708.img.tar.bz2

Next we create empty files for the filesystem (2GB) and swap (256MB) : 

cd /home/xen/domains/centos
dd if=/dev/zero of=Cent_base.img bs=1024k count=2048
dd if=/dev/zero of=Cent_swap.img bs=1024k count=256

mkfs.ext3 Cent_base.img

mkswap Cent_swap.img

Next we mount the img file from jailtime.org and copy everything to our empty img file : 

mount -o loop centos.5-2.64.img /mnt/img
mount -o loop /home/xen/domains/centos/Cent_base.img /mnt/vm1
cp -a /mnt/img/* /mnt/vm1/

Edit the network configuration file : 

vi /mnt/vm1/etc/sysconfig/network-scripts/ifcfg-eth0

and make it look like this (modify according to your network settings) : 

TYPE=Ethernet
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=static
IPADDR=192.168.0.100
NETMASK=255.255.255.0
GATEWAY=192.168.0.1

Next, modify the hostname : 

vi /mnt/vm1/etc/sysconfig/network

NETWORKING=yes
HOSTNAME=centos.example.com

Add your nameservers to resolv.conf : 

vi /mnt/vm1/etc/resolv.conf

Change this according to your NS : 

nameserver 24.200.241.37
nameserver 24.201.245.77
nameserver 24.200.243.189

Next we allow root login thru SSH : 

vi /mnt/vm1/etc/ssh/sshd_config

and modify PermitRootLogin option : 

[...]
PermitRootLogin yes
[...]

Next we copy some files : 

cp -av /lib/modules/`uname -r` /mnt/vm1/lib/modules/

A little tweak needs to be done to access the VM in console mode : 

vi /mnt/vm1/etc/inittab

find :

[...]
1:2345:respawn:/sbin/mingetty tty1
[...]

and replace with : 

[...]
1:2345:respawn:/sbin/mingetty console
[...]

Now we can unmount both img files : 

umount /mnt/img /mnt/vm1

Now we will configure the VM : 

cp /home/xen/domains/centos/centos.5-2.64.xen3.cfg /etc/xen/
vi /etc/xen/centos.5-2.64.xen3.cfg

and make it look like this (change kernel version if you have something different than 2.6.24-23, try 'uname -r') : 

name = 'cent5'
 
 
kernel = '/boot/vmlinuz-2.6.24-23-xen'
ramdisk = '/boot/initrd.img-2.6.24-23-xen'
memory  = '256'
 
 
root    = '/dev/sda1 ro'
 
disk    = [ 'tap:aio:/home/xen/domains/centos/Cent_base.img,sda1,w', 'tap:aio:/home/xen/domains/centos/Cent_swap.img,sda2,w' ]
 
 
dhcp = 'dhcp'
vif  = [ '' ]
 
 
on_poweroff = 'destroy'
on_reboot   = 'restart'
on_crash    = 'restart'

Delete the files from jailtime.org :

rm -f /home/xen/domains/centos/centos.5-2.64.*

Now you can finally create the VM :

xm create -c /etc/xen/centos.5-2.64.xen3.cfg

Login as root, password is 'password'

To put this on a partition for better performance, read this article

Reference : http://www.howtoforge.com/create-centos5.2-domu-on-ubuntu-hardy-dom0