Remove Old Kernels

This script will prevent the disk filling up with unused kernels, by only keeping the most recent N (3 by default) versions. If last-good-boot is enabled in /etc/default/kernel-helper-rc then this version is never removed either, and neither is the currently running kernel.
Recent versions of GRUB hide old versions, but they are still installed forever, and no one ever needs to go back more than a version or two ("argh, that update broke my ... how do I boot something that works"). This behaviour is present by default in distributions like Fedora.

Please note, the DUMMY_RUN setting should not be changed to 0. This will prevent updates from installing. There is probably no way to make things work using my approach. Instead you'll need to cut and paste the output by hand, or vote for https://blueprints.launchpad.net/ubuntu/+spec/desktop-q-clean-old-kernels

Install
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Open a console window (press ctrl-alt-f1, or use the GUI to start Terminal, Konsole, Xterm, etc) and run:
sudo add-apt-repository ppa:bugs-launchpad-net-falkensweb/remove-old-kernels && sudo apt-get update && sudo apt-get install remove-old-kernels

Configuration
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Configuration is done using a text file called /etc/remove-old-kernels.conf
Currently you *must* edit this file and set DUMMY_RUN to 0 or the script simple prints out the command it would run.
The contents of this file should be the 5 lines below.

#The number of old kernels to keep around
NUM_TO_KEEP=3

#Change to 1 to print out the command to be run but not run it
DUMMY_RUN=1

Usage
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The old kernels will be uninstalled the next time a new kernel is installed. Currently you must edit the configuration file for this to take effect, see above.