Upgrading MAAS from 1.5.4 to 1.7.0 or latest on ubuntu 14.04

I had this question myself and newell from the IRC channel helped me out in realising that the PPA was missing, but this might not be your case. These steps will help you get the update without compromising your other packages (please read the answers to the linked questions, they might be useful to your case and needs).

1. You should check if there are any held back packages, and if maas is one of them, when you do:

   sudo apt-get update && sudo apt-get upgrade
   

   If there are, and they are maas related, you can skip the following step, to add the Maas PPA.

2. To add the Personal Package Archive (PPA) for Maas's stable version (ppa:maas-maintainers/stable) you can do

   sudo apt-add-repository ppa:maas-maintainers/stable
   

   One normally installs Maas on a server so apt-add-repository or add-apt-repository, are not available. To install apt-add-repository/add-apt-repository, in order to add the ppa, use the following How to add a PPA on a Server?. After adding the ppa use the command from step 1.

3. Assuming you see held back packages, this means that the software you are to upgrade has new dependencies that it did not have on the version you currently have installed. You can have maas (or any package in this situation) installed by doing:

   sudo apt-get install <list of held back packages>
   

   You could do a sudo apt-get dist-upgrade, but it would mean getting more than just the held back software listed on apt-get upgrade. The latest version of ubuntu would also be installed. I took this information from here (the link points to the answer I used, the others hint at the fact that dist-upgrade and other commands, such as aptitude, might do more than what you want).