Having been a Zimbra Administrator for some time and having always worked on the Zimbra Open Source platform I have found that documentation on the update process has been very much lacking. The process is actually quite simple and straightforward under most circumstances but for someone without direct experience with the process it can be rather daunting.
My personal experience with Zimbra, this far, is running the 4.5.x series on CentOS 4 (RHEL 4). Using CentOS instead of actual Red Hat Enterprise Linux presents a few extra issues with the installer but have no fear, the process does work.
While this document is based on the Red Hat Enterprise Linux version of Zimbra, I expect that non-RPM based systems will behave similarly.
To upgrade an existing installation of Zimbra, first do a complete backup. I cannot state the importance of having a complete and completely up-to-date backup of your entire system. Zimbra is a massive package that is highly complex. You will want to be absolutely sure that you are backed up and prepared for disaster. If you use the open source version of Zimbra, as I do, that means taking Zimbra offline so that a backup can be performed. I won’t go into backup details here but LVM or virtual instances of your server will likely be your best friend for regular backups. Email systems can get very large very quickly.
Go to the Zimbra website and download the latest package for your platform. If you use CentOS, get your matching RHEL package. It will work fine for you. I find that the easiest way to move the package to your Zimbra server is with wget. Downloading to /tmp is fine as long as you have enough space.
Unpack your fresh Zimbra package. Zimbra downloads as a tarball (gzip’ed tar package) but contains little more than a handy installation script that automates RPM deployments. It is actually a very nice package.
tar -xzvf zimbra-package.tar.gz
You can cd into your newly unpacked directory and inside you will find that there is a script, install. Yes, the installation process is really that simple. If you are on most platforms you may simple run the install script. If you are on CentOS, rather than RHEL, you will need one extra parameter: –platform-override.
Be prepared for this process to run for quite some time, by which, I mean easily an hour or more. Depending on the version of the platform that you are upgrading from and to you may find that this process can run for quite some time. Also, depending on the size of your mail store, that may impact the speediness of the process as well.
The installation script will fire off checking for currently installed instances of Zimbra, checking your platform for compatibility (be sure to check this manually if using the override option but CentOS users can rest assured that RHEL packages work perfectly for them), performing an integrity check on your database and checking prerequisite packages. Chances are that you will need to do something in order to prepare your system for the upgrade.
In my case, upgrading from 4.5.9 to 5.0.9, I needed to install the libtool-libs package.
yum install libtool-libs
While there are processes here that can certainly go wrong, the Zimbra upgrade process is very simple and straightforward. As long as you have good backups (make sure not to start Zimbra and receive new mail after having made you last backup) you should not be afraid to upgrade your Zimbra Open Source system.
You can also purchase a support contract from Yahoo/Zimbra so that you can move to the Network version of Zimbra and Zimbra support staff are happy to walk you through the process. Having someone there to make sure everything is okay is always nice.