What is the 'recommended' way of upgrading Plesk 7.5.4 on Debian 3.1 (sarge)? Of course I'm planning to upgrade Debian as well to 4.0 Etch. The cleanest would probably be with migration manager to a new server, but that would probably take many hours for 400 domains with all sites offline (otherwise how can I guarantee perfect sync of two servers?) which is clearly unacceptable. So probably the fastest option with minimum downtime would be: a) upgrade Plesk to 8.4 (via web interface or CLI?) b) dist-upgrade sarge to etch Somehow I doubt it will go this smoothly, so I have a clone of the production server where I can test the procedure prior to actual upgrade. But here comes another question - what happens with the license key? As I understand, the upgrade procedure automatically upgrades the license key? Now, what happens with the license key if the upgrade goes haywire and I need to restore the original 7.5.4 version? Thanks in advance for any tips!