I had migrated some of the old machines at work to Xen hypervisor VM. The procedure is rather straight forward and with many options. In this post, I used simple dd command to migrate physical machine to a flat file image on Xen server.
DD IN ACTION
debian-HP370:~/ # dd if=/dev/cciss/c0d0 | ssh me@xenserver cat ‘>’/home/xen/img/debian-HP370.img
This will take a long time depending on your disk size/network speed. So leave it there and go on with other stuff. After a couple of hours, you have the image transferred to Xen server.
TAILORING TO VM ENVIRONMENT
As the physical machine has smart array raid and VM has choices of disk options: IDE, SATA, physical partition under the VM guest, I mounted the image and edit /etc/fstab to reflect disk on VM. Mounting an image file with many partitions is simple. Firstly, offset value of the partition is required. This can be obtained via fdisk command.
xenserver:/home/xen/img # fdisk -lu debian-HP370.img
You must set cylinders.
You can do this from the extra functions menu.
Disk debian-HP370.img: 0 MB, 0 bytes
255 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytes
Disk identifier: 0×111f5759
Device Boot Start End Blocks Id System
debian-HP370.imgp1 * 63 102269789 51134863+ 83 Linux
debian-HP370.imgp2 102269790 106655534 2192872+ 5 Extended
debian-HP370.imgp5 102269853 106655534 2192841 82 Linux swap / Solaris
The offset value in this example is 63 * 512 = 32256
Note : 63 is the Start sector of the partition that I wanted to mount.
xenserver:/home/xen/img # mount -o loop,offset=32256 debian-HP370.img /mnt/stuff
Next, you can just vi /mnt/stuff/etc/fstab, to suit your Xen VM configurations. We are almost done.
CREATING NEW VM
Creating a new VM is rather easy. You need a configuration file for VM guest. Please refer to example and wiki for complete parameters. Just run xm new <configure file> i.e. xm new debian-vmconfig or else use vm-install and be prompted with bunch of questions for configuration parameters. Sample HVM configuration file for my VM:-
name=”Linux-debian-HP370″
memory=1024
maxmem=2048
vcpus=2
on_poweroff=”destroy”
on_reboot=”restart”
on_crash=”destroy”
localtime=0
keymap=”en-us”
builder=”hvm”
extid=0
device_model=”/usr/lib/xen/bin/qemu-dm”
kernel=”/usr/lib/xen/boot/hvmloader”
boot=”c”
disk=[ 'file:/home/xen/img/debian-HP370.img,sda,w', ]
vif=[ 'mac=00:16:3e:51:16:ee,bridge=br0,model=e1000', ]
stdvga=0
vnc=1
vncunused=1
apic=1
acpi=1
pae=1
serial=”pty”
START THE MACHINE, LITERALLY
At this point of time, you should turn off the physical machine to avoid IP address clash. There is one last step to go which is the editing grub on VM. You could just fire up the new guest VM with xm start Linux-debian-HP370 && xm console Linux-debian-HP370 and hit “e” at GRUB menu to edit kernel parameter for root disk. Lastly, modify /boot/grub/menu.lst to reflect your root partition. Remember to run update-grub after finished editing.
OPTIONAL
Since my xen is a headless box, I have to go extra mile to get into the console by ssh tunnel.
ssh me@xenserver -L 5900:127.0.0.1:5900
Connect vnc to localhost will give you the new shinny VM console.
