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Re: [rhelv5-list] OT: migrating RHEL hosts

Copying the bits over the network seems to work.  I have copied the bits remotely to and from a disk image, rather than from the actual device on the original server, but I don't see why copying directly from one host to another would be a problem.

We use the same size SAN presentations on both sides.  It would probably be convenient to run a Fedora live CD on both the server being copied to and from, so the disks aren't mounted on either side.  Once you get the network set up on both sides, you can run a command like the following on the new server:

$ ssh user original_host dd if=/dev/sda | dd of=/dev/sda

I've not had much success lately trying to use the multipathed devices from the live CDs, but I've not had a problem copying to just on of the paths (e.g. /dev/sda).

This will replace the partition table and everything on your new drive, and replace it with the exact image that was on your old server.

You might have trouble booting the new server because the multipath uuid seems to get placed in the init script in the initrd.  Since the multipath uuid will likely be different on the new server than it was on the old, you may have to unpack your initrd, edit the init script (I would just have it run multipath with no uuid arguments), and package it back up.  You might want to delete the /var/lib/multipath/bindings file in both the initrd and in the real var filesystem as well.

If you try this approach and run into any problems, let me know what you find.

Good Luck!

On Fri, Jul 31, 2009 at 9:50 PM, Vanco Backup <vanco backup gmail com> wrote:
I was hoping to get some input on methods best suited to migrate a
series of RHEL(5U3) hosts.

The environment is straight-forward - Sites A and B are both home to
IBM Blades and an IBM SAN.  The Blades are the same, but the SANs
differ slightly (Site B being newer)

The Blades boot from SAN - no local disk.

There is a 1Gb IP link between them. I assume it's routed.

I've thought about trying to make a Live CD for either site that has
DRBD installed (via CentOS packages) and using the SAN LUN as the
device to be replicated.

I've thought about trying to use cobbler to basically bare metal
restore the remote site.

Has anyone done anything similar?  Obviously, looking for the easiest way out :)


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