Xen: Converting a physical linux machine to xen virtual machine (fully virtualized) in Redhat Enterprise (64-bit)

I am running Redhat Enterprise Linux with xen virtualization. My server is a quad core 3ghz IBM x3550 server with 20gb of ram.

Today I had a need to move a standalone linux box into a xen vm. I had to keep the standalone machine completely intact as it was a build server which compiled code. The purpose of moving the build server to a xen VM was to test a build and see how long it took on the new VM machine compared to the older standalone server. The build server was fedora core 6 but I imagine this post applies to any machine, any software.


Preparing the standalone server

1. Shut down the standalone machine
2. Connect external USB disk to the system (use a disk that is larger then the drive in the system)
   
3. Boot the standalone system with a linux boot cd (I used a ubuntu live recovery disk)
4. Once the machine has booted the live cd, mount the external USB drive
5. Use dd to make an image of the drive in the standalone server and output the image to a file on the USB drive: dd if=/dev/sda of=/mnt/usbdrive/standalone-server-image.dd (This will take some time)
6. Once DD has completed, go ahead and shutdown the standalone machine, remove the USB drive, remove the Live CD and boot the machine back up to normal operation (if you will continue to use the standalone machine)

Preparing the Xen Server

Note: I am using LVM for my VM's. If you are not sure what this is, dont follow these instructions word for word

1. Create a LV a little bit bigger then the original drive you imaged (my original was 80gb and I created a LV 100GB): # lvcreate -L100G -n newserver_vm /dev/data
   
2. Copy the image of the standalone server to the new LV you just created:# dd if=/mnt/usb/standalone-server-image.dd of=/dev/data/newserver_vm
   
3. Create a Xen configuration file for the new virtual machine (usually located in /etc/xen/

# /etc/xen/newserver_vm

import os, re
arch = os.uname()[4]

#I had to change the line below to match the path of where hvmloader was
kernel = "/usr/lib/xen/boot/hvmloader"

builder='hvm'

memory = 512
shadow_memory = 8

#change the line below to reflect the name of your vm
name = "newserver_vm"

#change the line below to match your network bridge. I copied and pasted this line from
#another working VM in xen that I started from scratch. Xen networking is a whole another
#blog!
vif = [ "mac=00:16:3e:15:f5:a6,bridge=xenbr0" ]

# I had to change the line below to match the patch of qemu-dm
device_model = '/usr/lib64/xen/bin/qemu-dm'
# boot on floppy (a), hard disk (c) or CD-ROM (d)
# default: hard disk, cd-rom, floppy
boot="dc"

sdl=0
vnc=1
vnclisten="0.0.0.0"
vncconsole=1
stdvga=0
serial='pty'

on_poweroff = 'destroy'
on_reboot = 'restart'
on_crash = 'restart'

#make sure this matches the LV you created and copied the standalone image to
disk = [ "phy:/dev/data/buildserver_vm,xvda,w" ]

Start the new VM

# xm create /etc/xen/newserver_vm

Once I started the new VM I used the gui xen manager in redhat. I could not get to the console from command line by starting the vm with "-c"


I hope this helps. This is made more as a reference then a step by step guide. Feel free to comment back with questions or suggestions.