How to clean Ubuntu's /boot if it has run full
After some time a kernel update may tell you something along the way of "Hey, there is a kernel update, but I can't update it because there is no space left on /boot".
To solve this you'll have to do a little apt-cleaning.
First find out which kernel you are using at the moment with
After this get the list of currently installed kernels with
sudo dpkg --list 'linux-image*'
Now remove all kernels except the current and maybe the one before that by using
sudo apt-get remove linux-image-X.X.XX-XX-generic
When you are done with removing, clean up orphaned dependencies with
sudo apt-get autoremove
And you should be done. You'll likely have to do this every few months again I'm afraid.