For my own comfort I am documenting this little (but essential) tidbit on my blog: How to “Remove Old Kernels In Ubuntu With One Command“. It’s a post from 2010, but it should work, according to the comments. I will admit, however, that I handled my current problem using the (manual) instructions I found on “Ask Ubuntu”.

Here’s what I saw (with a larger number)
I have been updating my system regularly, as it should, since the initial installation. Using the manual instructions mentioned, I managed to delete all 4.2 kernels and more.
Admittedly, I also issued these commands:
> sudo apt-get clean
and
> sudo apt autoremove
Yes, that last one uses ‘apt
and not ‘apt-get
‘ – that’s how it was spelled somewhere, and it cleaned up a lot of stuff! I’m not sure if it’s best or safest way to make sure you’re only running the latest installed kernel, though. I know Linux is for geeks <grin />, but I can’t help agreeing with one of the commenters on the post mentioned: “There’s no excuse Ubuntu doesn’t do some kind of automatic cleanup…“, or at least does so with a single, simple command or tool.