Two years ago this month, I reported here on my experience in installing Mathematica 8 in Linux (

Now I can report on installing Mathematica 9 in Linux.

The best thing to report is that this installation went even more smoothly than my previous one. This time I simply followed the current installation instructions on the Wolfram Research Website:

Mathematica 9 for Linux downloads as a script file:
I used the default locations in the script in installing it on my desktop, but it would have been easy to change to other locations if I had wanted to do so.

The installation script concludes with a hyperlink to instructions for activating the new installation:
I had no trouble with the activation (well, that is, once I started using my Activation Key for Mathematica 9 rather than the outdated Key for my Mathematica 8 installation).