Thanks for the info! Yeah, it's an older server with a few domains on, so I was trying to get it all the way to Fedora 11
Plesk 9 currently does not support Fedora 11.
but the only way to safely do this seems to be release-by-release.
I wouldn't even call that approach safe. I never do OS upgrades on a live production system. I always bounce the data to a new server if an OS upgrade is needed (we run CentOS, so it's rarely needed as a CentOS release gets 7 years of security updates and the hardware usually doesn't last that long). That way you can always fall back on the old system if something went wrong with the migration.
I think I'll try and get hold of another 1and1 server and stick Centos on that using the AtomcRocketTurtle scripts...
That sounds like the way to go, yeah.