source: trunk/server/doc/migrate @ 2577

Migrating a Scripts guest between Xen hosts
-------------------------------------------

Two main components:

    1. Copying the disk image (we do this with dd/netcat/backend network)
    2. Modifying Xen configuration

First, get a copy of /etc/fstab; in particular, you care about the UUIDs
of the swap and cache partitions.

Next, shut off the relevant VM.  Make sure that you have space on the
destination host, and that you have a volume ready to receive the data
(check with 'lvs').  From now, we'll assume $MACHINE is the name of the
VM you're migrating, $SRC is the source host, and $DST is the destination host.

Setup dd listening on a port on the destination host.  Pick a random,
hard to guess port number.

    root@$DST:~# nc -l -p $RANDOMPORT | dd of=/dev/$DST/$MACHINE-root bs=16M

Next, send the data over the *backend network*.  We have 172.21.*.* setup
to be routed on our backend network, do NOT use the public IPs on 18.*.*.*.

    root@$SRC:~# dd if=/dev/$SRC/$MACHINE-root bs=16M | nc 172.21.X.Y $RANDOMPORT

where X and Y are the last two digits of the normal 18.181.X.Y IP address of $DST.

Once you're done, ensure that the swap and cache partitions are ready on the
destination (you don't, mercifully, have to dd those over)--make sure they're
properly configured; especially make sure that they the right UUIDs (from
the fstab you saved!)  Check 'install-fedora' if you need to be reminded
what the incants are.

Finally, edit /etc/xen/scripts and modify the host that is hosting the server.
Spin it up on the host and make sure everything is in order, then nuke the
old disk image (multiple copies of a Scripts server is a bad idea!)