We have a stable but out of date system, it is running on dell hardware and in general we have no issues.

Probably due to that stability of the system, we are now seriously out of date with the OS reaching EOL and our Zimbra on a very old version.

I would like to swap OS to Ubuntu - and bring the zimbra to the latest version whilst keeping our existing hardware.

I believe the steps would be.

Backup whole machine.
Zimbra dump of ldap etc.
install fresh OS
Restore data and configure machine as it was
install zimbra 5.0.13 (same as current version)
Restore zimbra
Upgrade zimbra.

Or perhaps... upgrade zimbra to 7 or possibly 8 and then...

Backup whole machine.
Zimbra dump of ldap etc.
install fresh OS
Restore data and configure machine as it was
install zimbra (same as current version)
Restore zimbra
Upgrade ZCS to 8.x


I personally think that the second path would be best, but there might not be an easy upgrade to Zimbra 7 from 5.... and Zimbra 7 is still supported on centos 4.8, though i am worried that if i have to install any rpm the standard repos are now offline.

I would welcome any suggestions, gotchas, links or lists which might help with this..