For apt-based software management systems, including the n810, from a command line you can run two commands:

(1) apt-get clean

(2) apt-get autoclean

The first removes the left behind files other than lock files. The second removes package files that can no longer be downloaded (because you have a newer versions installed, for instance).

You can check out the apt-get man page for more apt goodness here:

http://www.debian.org/doc/manuals/ap...pt-get.en.html

You will see your /var directory shrink substantially using these, usually.

Edit: oops, forgot to mention that you'll need root access to get permission to the /var directories to do this.