Here's how I updated my server's Ubuntu from 11.10 to 12.04 LTS.
I don't have a desktop installed on the server, so I had to run the upgrade from terminal. I have a forum running, a lot of MySQL databases and Apache 2 on the server. I'm also running sensord and other stuff like that. So some of the software will probably need some configuration.
I logged on my server as root and ran
I installed all the updates, except new versions of the kernel. Maybe it's even better if you run
... which will install a new kernel version.
Then, using nano I edited the /etc/update-manager/release-upgrades file:
I changed it to read:
Then the update can be started:
You might need to install the update manager first:
apt-get install update-manager-core
So the install started running, and quickly I was asked if I wanted to change the MySQL database root password. I chose not to, by leaving the field blank. This will keep the old password. Somehow, I was asked again for this two times...
Then I was asked if I want to be prompted when services are restarted during the upgrade. I chose not to, to make the upgrade process faster.
Then another question about the MySQL server password. I'm starting to think I should have set one in the first place... How times will it still ask me?
Then came a question about sensors3.conf. The file has been modified but a new version is available. After checking the differences between the files, I chose to take the new version. There was no important changes in the file.
Fifth MySQL root password question... Left it blank again.
Then a more important question. "A new version of configuration fiel /etc/php5/apache2/php.ini is available, but the version installed currently has been locally modified. What do you want to do about modified configuration file php.ini?"
There was an option to see what changes had been made to the file in the new version and on my local version. I had set the post_max_size and upload_max_filesize to bigger values. Since there were many changes to the php.ini in the updated version, I chose to take that one and just do my custom changes again.
Next question: "Remove obsolete packages? 33 packages are going to be removed." I checked the packages and none seemed important - newer versions were probably already installed.
Finally, the upgrade was complete. After a reboot, the system was running 12.04. BUT, only SSH was usable. Somehow the display adapter was just blinking a gray picture on my screen... Oh, well. Luckily, I didn't even need the display adapter - I just removed it and switched to using the integrated adapter of the server PC. That one worked fine, so why bother trying to get the other one working.
So, there's my experience of upgrading to 12.04 LTS. Some problems, but the end result is what matters: the server is now upgraded and working fine!