Had a successful migration form 7.13 on Ubuntu 8.04 to 7.2 Ubuntu 10.04 ( all 64 bit edition since 7.2 will be deprecated on ubuntu 8.04 )

Steps :

Do all updates on Ubuntu
apt-get updates
apt-get upgrade

Disable zimbra on boot up. ( use webmin interface )

Upgrade to 7.2 ZCS for Ubuntu 8.04 version
Say yes for MYSQL db integrity check.
Upgrade sucessfull, however amavisd ( for antispam/antivirus ) will not start because of FQDN error.

Make changes to /opt/zimbra/conf/amavisd.conf.in ( the .in file overwrites the amavisd.conf everytime amavis services is launched.
Correct FQDN approrpriately.


Restart amavis using command amavisdctl restart
Start successful.

Very zimbra services are restarting properly -
zmcontrol stop / start

All good

CLone or Backup your VM.

Proceeded with upgrade to Ubuntu 10.04 LTS

Shutdown ZImbra services.

apt-get install update-manager-core

The minumum contents of /etc/update-manager/release-upgrades should be

[DEFAULT]
Prompt=lts

do-release-upgrade

Answer yes to pretty much all the requests in the upgrades.

Upgrade finished.

Launched ZImbra but it won't start at all :
Some error about perl came up.
Did some research on perl which comes standard with 10.04.

see this post
Perl_Tstack_sp_ptr error after upgrade Unbuntu 8.04 to 10.04 and zcs 7.1.1 to 7.1.2

Proceeded to delete
deleted /opt/zimbra/zimbramon/lib/x86* directory where perl resides.

THen upgraded to 7.2 ZCS for UBUNTU FOSS ( 10.04 ) edition.
PLEASE DO NOT ACCEPT MYSQL INTEGRITY CHECK AS IT REQUIRES PERL.

Upgrade to 7.2 FOSS successfull.
with amavis ( antispam/antivirus ) still down.
redo the same thing for amavisd.conf.in as described above.

Zimbra 7.2 UBUNTU FOSS started like a charm.

Checked all logs and tested emails and access to admin console.

- Applied open vm tools on the fly

apt-get install linux-headers-virtual
apt-get install --no-install-recommends open-vm-dkms
apt-get install --no-install-recommends open-vm-tools

VM tools installed ( on vmware console it will read unmanaged )
Next step now is to script a zimbra cron job to stop zimbra services - Veeam Backup the VM and restart zimbra for automation.

Good luck to you all.