I've been successful installing ZCS 6.0 on a Ubuntu 8.04 x64 server to replace a ZCS 5.0.18 on CentOS 5. The decision was made to recreate all of the accounts because there was a major SAN issue in the past that damaged the CentOS install, along with a failed update to 5.0.18 (it ran like molasses ever since). Anyways, the system is fully functional and zmcontrol status reports say all services are active and running (great!). However, inside of the zimbra Admin Console, it seems that the servers do not communicate well with one another (the GUI does not display the status of the other servers, they merely have X's around server names and all of the server statistics). I think there is a problem between the communication between the servers. I ran zmupdateauthkeys (which I assume allows the servers to ssh into one another), however a simple test after su - zimbra (ssh -l zimbra ) didn't work at all.