First problem I've encountered with Ubuntu was trying to use Facebook's photo uploader from Firefox. It all started out well: I went to the the page and was told I needed to install Java, and Ubuntu presented me with a list.
Here is where I made my first mistake, I installed the first one on the list, which wasn't Sun's JRE. I can't remember the name of the one I installed, but after sitting through the installation I got back to Facebook and had a dialog pop up saying the GNU classpath had not been set, or something along those lines anyway.
So I went to verify my Java plugin, and got a message saying I wasn't running the latest version, and provided links to download the latest. Not really knowing what an RPM was, I chose the "Linux (self extracting file)" option, and consulted the instructions.
Second problem came now. The first instruction was to SU to root, which required a password, and I'm pretty sure I never set a root password when I installed.
But no problem, I just chose System - Administration - Users and Groups from the top menu in Ubuntu, selected the root user and assigned a password. I then carried on following Sun's instructions to install Java, which were simple enough.
Then came the section Enable and Configure, in which I had to tell Firefox to use this new JRE for applets.
Neat little tip that I didn't know about in Firefox is that if you type about:plugins in the address bar you're given a list of the installed plugins, which I was able to use to remove the old plugin that didn't work.
The plugins are just symbolic links in the firefox/plugins directory, so enabling one plugin means creating a new link in there, and removing the other effectively uninstalls the old one.
Job done, Facebook's photo uploader (and I assume other Java applets) now works properly.
