I have a ubuntu 7.10 test server and hope I can help...
the normal method to start zimbra by hand on ubuntu is:
or to do it a the zimbra user....
sudo /etc/init.d/zimbra start
But I am guessing you are having a permissions problem.
(become the zimbra user)
# sudo su - zimbra
# zmcontrol start
If at some stage you have run zmcontrol as "root" then the "zimbra" user will not be able to start the server anymore as lots of the files it needs to read and write belong to root i.e. you should see permission denied in the logs
To try fix this do the following:
some other checks:
run the following:
On my system it returns "N 2" meaning runlevel 2
Now check the start an kill links are correctly set, for this I check in "/etc/rc2.d/"
hope this helps!
ls -l /etc/rc2.d/*zim*
lrwxrwxrwx 1 root root 18 2008-03-30 15:05 /etc/rc2.d/K01zimbra -> /etc/init.d/zimbra
lrwxrwxrwx 1 root root 18 2008-03-30 15:05 /etc/rc2.d/S99zimbra -> /etc/init.d/zimbra