Replication - hostname issue

[Petter Gunnerud]

I have postfix/dovecot setup on a virtual gentoo server. It's been in service for almost two years without any issues.
Now I want to set up a spare server to replicate mails from the one running. I copied the vm files to the second host server, changed the ip, hostname and hosts file for the copy and followed the dovecot replication doc.
The last point in the doc tells to rundovecot --hostdomainto make sure the hostnames differ... To my surprise the command returned "localhost" on both servers.
How do I set the hostname for dovecot service?(The hostname command returns the servers hostnames.)Will a change in dovecot hostname make all clients redownload all their mail?

A second question. When configuring dovecot replication. Should the settings be done on the master server or the stand by server, or both? (Doc doesn't say anything regarding this)
PG