So, my web server was a little out of date, running Debian Squeeze. The HeartBleed vulnerabilty was a bit of a wake up call to get up to date (despite the fact I wasn't vunerable to it because of the server being out of date), and I decided to do a Dist-upgrade.
This went reasonably smoothly, except my customised qmail install isn't allowing me to send email (or more specifically it is, but then generating an error) so I'll need to fix that (I am getting mail though, so not too urgent)
It also broke mysql, and I hadn't taken the time to take backups of the databases before hand! (BIG mistake)
Fortunately I was able to fix that without any data loss.
I then Discovered that it had broken my blog. The data appeared to be in the database, but the blog wouldn't load. I tried taking a backup and reinstalling the blog. This Did not help much. Although that then pointed me in the right direction. The update had removed the mysql connector that I had linked into the tomcat lib folder. So I fixed it by linking the new mysql connector that had been installed as part of the upgrade.
The Biggest fail here being the lack of backups, or contingency planning, particularly given that this is what I do for a living!