All you need to do is install the RootSH package via App Manager.

http://maemo.org/downloads/product/Maemo5/rootsh/

Once that's installed, simply enter:


in XTerm, and you're golden


NOTE: there is also a package called "rush" in the repos that will give you a root shell just as rootsh will. To use that one, simply enter

into XTerm.


A bit easier, IMO


EDIT: it's worth pointing out that you don't need to 'root' the N900 the way you might want to 'root' an Android device -- all I've explained here is how to get yourself root access to the shell... if you don't know why you'd need that then don't bother