If you are using Ubuntu 10.04 LTS and were expecting Ubuntu 12.04 LTS to be available in the Upgrade Manager, you were wrong. Well, at least I was wrong…
Canonical won’t make it available via the Upgrade Manager in the first release, but only in July with Ubuntu 12.04.1 release, and the company recommends that most LTS users wait until then before upgrading to 12.04.
But if you can’t possibly wait that long, you can run:
to upgrade from Ubuntu 10.04 (Lucid Lynx) to Ubuntu 12.04 (aka Precise Pangolin). The first command will run in the terminal, the second will start the Update Manager and allow you to select “New Ubuntu release ‘12.04’ is available”.
For details on why you should NOT upgrade yet, see http://askubuntu.com/questions/125825/upgrading-lts-to-lts-server-why-wait-for-the-first-point-release.
The first time I tried to upgrade I had the following errors:
Could not calculate the upgrade
An unresolvable problem occurred while calculating the upgrade:
The package ‘update-manager’ is marked for removal but it is in the removal blacklist.
This can be caused by:
* Upgrading to a pre-release version of Ubuntu
* Running the current pre-release version of Ubuntu
* Unofficial software packages not provided by Ubuntu
If none of this applies, then please report this bug against the ‘update-manager’ package and include the files in /var/log/dist-upgrade/ in the bug report.
The first thing you can do to work around this issue to purge the PPA (Personal Package Archives) if you have any, for example:
sudo apt-get install ppa-purge
sudo ppa-purge xorg-edgers
Your ppa package source lists are located in /etc/apt/source.list.d. I could not remove any, possibly because they had already been disabled by the upgrader.
The next step you can do is to look for broken packages in /var/log/dist-upgrade/apt.log:
cat /var/log/dist-upgrade/apt.log | grep Broken
In my case, after uninstalling xserver-xorg-video-all:
sudo apt-get remove xserver-xorg-video-all
The upgrade process using “do-release-upgrade -d” could continue.