Updating your Zentyal Server
If you have installed using the official Zentyal installer, your repository list will be already pointing to the correct repositories for your version. Otherwise, you will need to include the following line in your /etc/apt/sources.list file:
deb http://archive.zentyal.org/zentyal <zentyal-version> main extra
deb http://archive.zentyal.org/zentyal 3.4 main extra
and then, retrieve the basic Zentyal components:
sudo apt-get update sudo apt-get install zentyal-core zentyal-software
From here, you can easily continue installing and configuring just using the web UI.
Take into account that each version of Zentyal Server is based on an specific version of the Ubuntu Server, for example, Zentyal 3.4 is based on Ubuntu Server 13.10. If you try to install a Zentyal Server version that was not based on your Ubuntu Server version, it's not going to work. Here you have the reference table.
The recommeded way of updating your Zentyal Server is through the module Zentyal Sofware. You can check the official documentation on how to use this module as part of the official doc: http://doc.zentyal.org/en/software.html.
This is a module that comes automatically installed if you use the Zentyal installer ISO, however, if you have installed manually on top of ubuntu server, you may not have it.
If you wish to install Zentyal Sofware, just make sure you have the correct repositories and then:
sudo apt-get update && sudo apt-get install zentyal-software
Updating to next community version
Sortly after the release of a new community version, if you have the Zentyal Software module installed, you will see a button in your Dashboard offering you the update between releases. Before performing the update, make sure that you have reliable network connectivity, and can afford a few hours downtime period. Take into account that the upgrade process will possibly upgrade the base Ubuntu Server version as well.