I am not a “real” system administrator but I manager sever VPS servers for my own web sites. This is what I did to update from Ubunutu LTS 10.04 to Ubunutu VPS 12.04.

1. I already have all the code and databases backed up, off the server, regularly. I backed up various things to another machine: sites-available files, cron directories, .bashrc, .profile, keys.
2. I tried running the preferred upgrade command

   [bash]do-release-upgrade[/bash]

   But got the message

   -bash: do-release-upgrade: command not found

   Then I ran

   [bash]sudo apt-get install update-manager-core[/bash]

   Then I was able to run [bash]sudo do-release-upgrade[/bash]

3. Which resulted in this somewhat scary message
   

   This session appears to be running under ssh. It is not recommended to perform a upgrade over ssh currently because in case of failure it is harder to recover.

   If you continue, an additional ssh daemon will be started at port ‘9004’.
   Do you want to continue?

   I look around on the web for advice. What’s the risk of upgrading over SSH? seems a good recap. I then continued. I then got this message

   To make recovery in case of failure easier, an additional sshd will be started on port ‘1022’. If anything goes wrong with the running ssh you can still connect to the additional one.
   If you run a firewall, you may need to temporarily open this port. As this is potentially dangerous it’s not done automatically. You can open the port with e.g.:
   ‘iptables -I INPUT -p tcp –dport 1022 -j ACCEPT’

4. 12 minutes after the upgrade started, the download was complete and I got a message to decide if I wanted to manually approve every restart required or just automatically approve them all. I chose the option to have all restart automatically.
5. Then lots of files were installed and I was asked about various files; where I (or some script) had changed (or deleted) the default file and now the upgrade wanted to replace the existing file. I had to guess what to do in those cases. They let you look at the diff between your existing file and the proposed overwrite. I think I would like it if they default behavior was to create a backup of the file in that same directory (you choosing whether to set your file or the updated file as active).

The entire process took exactly 30 minutes, with the system restarting in Ubuntu 12.04.

Thankfully the upgrade seems to have gone without causing any problems. This is normally the case. But, even with a very small likelihood of encountering issues it is worrisome as those issues might pose some serious problems. Especially for someone with very limited system administration ability.

I am extremely thankful for all the programmers that created the code to make this process so straightforward and reliable.

[bash]lsb_release -a[/bash]

lets you see the current Ubunutu version you are running.

When I updated a server that had Ruby on Rails applications everything almost worked fine. Passenger was unable to load the application talking about

libmysqlclient_r.so.16: cannot open shared object file: No such file or directory – /usr/local/rvm/gems/ruby-1.9.2-p290/gems/mysql2-0.3.11/lib/mysql2/mysql2.so

I was able to find the solution to that issue was to uninstall the mysql2 gem and then run bundle update: which worked great. The uninstall would work for me unless I was actually root (sudo didn’t work), so I used su to login as root and then

[bash]gem uninstall mysql2[/bash]

Then I went back to being my other user ran bundle update

[bash]bundle update rake[/bash]

Then everything was working fine.

Related: Keeping Your Hosted Ubuntu Web Server Software Up to Date – Adding a Key to Your Server for SSH Login – Checklist: Setting Up a New Domain on VPS