[CentOS-virt] Now on to creation of disk images

Tue Jun 28 14:50:16 UTC 2011
Ed Heron <Ed at Heron-ent.com>

On Tue, 2011-06-28 at 09:30 -0400, Steve Campbell wrote:
> Mr. Heron was so kind to make a suggestion that I should use disk images 
> to install VMs. Upon further thought, I kinda like the idea. So I 
> re-read the manual and google a little, and discover I still don't know 
> what should be in these disk images.
> Should I copy the contents of the CDs to a file or what? I've got a test 
> server at the moment with Centos 5.5 and xen installed as the host OS, 
> but have just downloaded the 5.6 CD ISOs along with the  DVD ISO, so 
> I'll use 5.6 for my VMs. I've read about how I can create an image from 
> something that already exists.
> Again, any clarity would be appreciated.

  Just put the ISO's in /var/lib/xen/images and point at them.  If you
didn't download the discs, you can rip them using:

dd if=/dev/<optical device> of=/var/lib/xen/images/<name of disc>

  For example, if ripping the first 5.6 CD...

dd if=/dev/hdc of=/var/lib/xen/images/CentOS-5.6-i386-d1.iso

I generally rip a disc multiple times and then do a file compare to make
sure I've got a reasonable chance of having an undamaged copy.

  Keep in mind that it isn't as easy to change discs when you are using
images on a paravirtual machine.

  I still recommend setting up a local repository as a much better
solution because it allows you to take a snapshot so multiple installs
use the exact same versions of everything.