Ubuntu constantly updates the linux kernel which is good. you get the latest security patches and software updates which makes a very secure system. A minor side effect is that the old kernels are not automatically removed from the system which, if left unchecked, can quickly fill up the /boot partition. The unused kernels can be removed using a gui like Synaptic:
sudo apt-get install synaptic
or Ubuntu Tweak:
sudo add-apt-repository ppa:tualatrix/ppa sudo apt-get update sudo apt-get install ubuntu-tweak
but you have to install these applications first.
I prefer to use the terminal.
Check the kernel version that’s currently in use. Do not delete this kernel else your ass is cooked:
List all the kernels in the system:
dpkg --list | grep linux-image
From thee list generated above determine the kernel you want to remove from system and then issue the following command:
sudo apt-get purge linux-image-x.x.x.x-generic
replacing the x’s with the kernel version you want to delete.
When you’re done issue:
to update the boot configuration file (grub.cfg).