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atjensen11 28th February 2009 19:40

Virtualizing a Physical Machine
 
I have a physical Ubuntu 8.04 LTS server that is currently configured to use one 250 GB HDD. I wrote a backup script that runs nightly using the TAR command to backs up all of the data directories to an external HDD.

I would like to virtualize this machine on a new production server that I have installed which is running Xen. This machine is setup to use LVM for the DomU machines.

Setting up the DomU is not an issue. I would like to move the data from the physical HDD to the newly created DomU LVM partition.

The problem is that I setup the physical machine with only two partitions (root & swap). It was the first machine I setup and I have learned a lot since then. Therefore, the root partition consumes most of the 250 GB HDD, but there is nowhere near that much data on the drive. The data could easily fit in a 50 GB partition.

I was thinking of creating a new LV on the DomU machine and using the DD piped through SCP to copy the data from the physical machine to the LV on the Xen host. In order to do this, I am pretty sure that I need to create the LV with the same size as the physical HDD, 250 GB. I have enough size on the new machine to do this, but I don't want to allocate that much space to this DomU permanently.

Can I shrink this LV easily after the move? The physical HDD and the newly created LV would both have Ext3 filesystems.

deshantm 1st March 2009 05:31

Re: Virtualizing a Physical Machine
 
Your plan seems reasonable in a general sense, but I would suggest a couple things to consider:
I don't think you need to actually dd the partitions, I would instead suggest to use tar to tar the root file system, then simply untar it onto the domU partition (LV or otherwise is fine).

Another easy way to go from physical to virtual is to boot from a liveCD, mount the partition or LV needed for the domU guest over NFS then simply do a cp or tar+cp being careful with the options to cp and tar so as to handle things like symbolic links properly.

If you are new to the xen and don't have a copy of "Running Xen", as a co-author I recommend it.

There are similar examples of watching out for things like /etc/fstab, partition labels, and the like covered in the book. As well as detailed information on working with LVM and domU guests.

Take a look into it with a google book search for LVM:
http://books.google.com/books?id=XS-...zyDg#PPA283,M1

The website for the book is:
http://runningxen.com

Even if you decide you don't want to buy there are lots of free references on the site itself.

Hope that helps.

Cheers,
Todd


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