Started with Ubuntu 8.04.4 x32 NE6.0.8, went to Ubuntu 8.04.4 x64 NE6.0.8, using the instructions at Network Edition: Moving from 32-bit to 64-bit Server - Zimbra :: Wiki

First deviation from instructions involves SSL certificates:
even though this is a 6.0.8, and this server has commercial certificates installed, /opt/zimbra/tomcat/conf/keystore didn't exist. It was upgrade from a 5.x install at least 6 months ago, but it looks like /opt/zimbra/mailboxd/etc/keystore was still in use. I copied it to the same place (/opt/zimbra/mailboxd/etc/keystore) on the new install. Biggest reason was that/opt/zimbra/tomcat doesn't even exist on either box. Hrmm?

I'm also concerned that this instuction is insufficiently specific - in other words, I'm afraid I've missed something here:

The postfix certificates (smtp) are /opt/zimbra/conf/smtpd.crt and smtpd.key. If you are using the certificates for nginx, perdition, or ldap (slapd) they are also in /opt/zimbra/conf/; they should normally be identical to the postfix certificate files.
Here are the errors I get during startup

Code:
zimbra@zimbra:/root$ zmcontrol start
Host zimbra.{mydomain}.com
	Starting ldap...Done.
	Starting logger...Failed.
Starting logswatch...failed.


	Starting convertd...Done.
	Starting mailbox...Failed.


	Starting memcached...Done.
	Starting imapproxy...Done.
	Starting antispam...Done.
	Starting antivirus...Done.
	Starting archiving...Done.
	Starting snmp...Done.
	Starting spell...Done.
	Starting mta...Failed.
Starting zmmtaconfig...zmmtaconfig is already running.
postalias: fatal: bad string length 0 < 1: mail_owner = 
postfix failed to start
Starting saslauthd...done.


	Starting stats...Done.
So - lets look at mailbox.log

I think the key piece here is

Code:
2010-11-06 21:38:55,841 WARN  [main] [] misc - Could not establish a connection to the database.  Retrying in 5 seconds.
com.zimbra.common.service.ServiceException: system failure: getting database connection
ExceptionId:main:1289093935841:c902435d5e8597f5
Code:service.FAILURE
so - lets look at zmmysqlstatus

Code:
zimbra@zimbra:~/mysql/share/mysql$ zmmysqlstatus 
ERROR 2002 (HY000): Can't connect to local MySQL server through socket '/opt/zimbra/db/mysql.sock' (2)
Error while running 'mysql --user=zimbra --password={my mysql password} --database=zimbra --batch --skip-column-names'. at /opt/zimbra/bin/zmmysqlstatus line 248.
looks related - so now I'll check the mysql password on the old server and make sure it matches this one.

Interestingly, "zmlocalconfig -s | grep mysql" reveals that they're set to use the same passwords, but that there are some somewhat major differences in the configs.

OLD 32bit SERVER
Code:
zimbra@zimbra-old:/root$ zmlocalconfig  -s | grep mysql
logger_mysql_bind_address = 
logger_mysql_data_directory = 
logger_mysql_directory = 
logger_mysql_errlogfile = 
logger_mysql_mycnf = 
logger_mysql_pidfile = 
logger_mysql_port = 
logger_mysql_socket = 
mysql_bind_address = localhost
mysql_data_directory = ${zimbra_db_directory}/data
mysql_directory = ${zimbra_home}/mysql
mysql_errlogfile = ${zimbra_home}/log/mysql_error.log
mysql_mycnf = ${zimbra_home}/conf/my.cnf
mysql_pidfile = ${zimbra_db_directory}/mysql.pid
mysql_port = 7306
mysql_root_password = {password}
mysql_socket = ${zimbra_db_directory}/mysql.sock
zimbra_logger_mysql_password = 
zimbra_mysql_connector_maxActive = 100
zimbra_mysql_password = {password}
zimbra_mysql_user = zimbra
NEW 64bit SERVER
Code:
zimbra@zimbra:/root$ zmlocalconfig -s | grep mysql
logger_mysql_bind_address = localhost
logger_mysql_data_directory = ${zimbra_home}/logger/db/data
logger_mysql_directory = ${zimbra_home}/logger/mysql
logger_mysql_errlogfile = ${zimbra_home}/log/logger_mysql_error.log
logger_mysql_mycnf = ${zimbra_home}/conf/my.logger.cnf
logger_mysql_pidfile = ${zimbra_home}/logger/db/mysql.pid
logger_mysql_port = 7307
logger_mysql_socket = ${zimbra_home}/logger/db/mysql.sock
mysql_bind_address = localhost
mysql_data_directory = ${zimbra_db_directory}/data
mysql_directory = ${zimbra_home}/mysql
mysql_errlogfile = ${zimbra_home}/log/mysql_error.log
mysql_mycnf = ${zimbra_home}/conf/my.cnf
mysql_pidfile = ${zimbra_db_directory}/mysql.pid
mysql_port = 7306
mysql_root_password = {password}
mysql_socket = ${zimbra_db_directory}/mysql.sock
zimbra_logger_mysql_password = 
zimbra_mysql_password = {password}
zimbra_mysql_user = zimbra
So, in digging around for logs for mysql (something I had a hard time doing since there were none created BECAUSE) I found that i didn't have a my.cnf. Not sure how I made it through a successful installation from scratch without one being created, but I did.

I've copied it over from the old 32bit machine and things look slightly better. Mailbox started, but mta still hasn't (because its already running? 0^o) - and neither has logger.

Code:
zimbra@zimbra:~/log$ zmcontrol start
Host zimbra.{my domain}.com
	Starting logger...Failed.
Starting logswatch...failed.


	Starting convertd...Done.
	Starting mailbox...Done.
	Starting memcached...Done.
	Starting imapproxy...Done.
	Starting antispam...Done.
	Starting antivirus...Done.
	Starting archiving...Done.
	Starting snmp...Done.
	Starting spell...Done.
	Starting mta...Failed.
Starting zmmtaconfig...zmmtaconfig is already running.
postalias: fatal: bad string length 0 < 1: mail_owner = 
postfix failed to start
Starting saslauthd...already running.


	Starting stats...Done.
The UI is accessible and the system apparently working (though who knows how well) so I'm going to post this, but will continue to dig around at why logger won't start, and why the mta would already be running.

If you have any light to shed on either of these issues (or anything you've seen above that is obviously a problem) please chime in. I'm running out of steam here...

Best to all and thanks,
Andy