Using Xen the Easier Way

The one and only one enterprise grade virtualization

software available in Open Source is Xen. It's highly secure, reliable and

works with minimum hardware overhead. But with all the positives there is also a

huge drawback-the configuration and installation is a nightmare.

Everything is done through command interfaces and by

modifying text configuration files. So, if you are not a Linux geek then this is

obviously not your cup of tea.

But there is something which can help you in deploying

this software in your enterprise. You can even test the performance of the

software and the guest



OSs



running on top of that before



deploying it.

This is done basically with the help of a Live CD which is

a customized Knoppix version with a Xen kernel. So, if you feel like testing Xen,

all you have to do is to boot the machine with the live CD and your Xen machine

will be up and running. This also comes with a pre-created Guest OS which has

the same kernel and file system as the Host OS. So, all you need to do to start

is, to run a simple



command:

$ sudo knoppixU

Running the Knoppix-installer will start a graphical interface like this. Now you can install the live CD on your HDD

More details on this command are available later  in

this



article. Whenever you feel that the application is good for your needs, you can

choose to install the Live CD onto your harddisk and configure more guest



OSs



of your choice. Here, we'll see how to go about it.

Installing Xen-Knoppix on the harddisk



I don't know whether you'll believe or not. The installation of Knoppix

nowadays is more easier than installing a standard Linux distro such as Fedora

or Debian. To do so, all you've got to do is to boot up your machine with the

Xen-Knoppix Live CD. Subsequently, open up the terminal and start the

installation with the following command:

#sudo knoppix-installer

Here, sudo command is used to start the installer with the

root privilege. If you don't use sudo then the application will terminate with

an error saying 'Permission Denied'. Now this command will open up a

graphical wizard. Just continue hitting OK or Next until you see a dialog box

which says 'Knoppix Partition Menu.'

Xen Knoppix has a very easy to use and completely graphical partition manager called qtparted

Here, select the first option which says 'Partition the

Hard Drive' and select Ok. This will open up a neat tool called parted. This

tool looks pretty similar to the PowerQuest Partition Magic. With the help of

this tool you have to create an ext3 partition and a swap partition. You can

have any specific size for these partitions. Just ensure that if you're

planning to have images of the partitions of the guest



OSs



in the same partition instead of having separate physical partitions, then

you should have a good amount of space in the ext3 partition. Now, create a swap

partition which is double the size of the amount of RAM you have. After you are

done with all of this, click on the floppy icon at the top left corner of the

windows which says 'Commit' to create the partitions.

Now close the application and you will be directed to the

previous wizard. On this window select the first option which says 'Configure

Installation' and hit Enter. After this, it will seek information such as the

'System Type' (here you can go with the default option), partition type

(select razorfs), username, password and the root's password. Fill in all the

fields with appropriate values. It will also ask you where you want to install

the Boot loader (grub in this case). Select MBR if you don't want to do dual

boot (not good or this type of setup). After you're done with all of this, the

'Knoppix Installer' will re-appear. Now select the second option from here

which says 'Start Installation' and within a couple of minutes the Live CD

will get installed on your machine.

Installing New Guest



OSs



Install another Linux distro (say RHEL, Debian) on some other partition of

your machine. To configure Xen, reboot the machine and when the boot options

show up, select 'Xen 2.0' and press Enter. This will boot up PCQLinux using the

Xen kernel — customized for virtual machine operations. Now you should be able

to login as root. Note that password, configuration and all other settings

remain the same as in the host OS. The only change is that we have booted with a

customized Xen kernel. Upon login, create a file named guest in /etc/xen

directory with:

kernel =

"/boot/vmlinuz-2.6.10-xen0"







memory = 128







name = "guestos"







nics = 1







ip = "192.168.1.1"







disk = <'file:/dev/hda6,hda6,w'>







root = "/dev/hda6 rw"

Substitute hda6 with the partition on which you installed

the guest OS.

Launch the guest OS



Open a terminal window in X and issue:

/etc/init.d/xend start

Then issue the following to launch the guest OS:

xm create -c /etc/xen/guest

vm=1

This should start the boot sequence for the guest OS and

let you login to the guest Linux OS. If you issue the ifconfig command on the

host OS, you will be able to see a virtual network interface named xen-br0.

Through this virtual interface the host OS will be able to access the guest OS

and the services running on it.

Anindya Roy