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Removing old Kernels in Ubuntu 16.04/Linux Mint 18

Recently I’ve noticed that my /boot partition has become full and I’ve even had some new kernel updates fail as a result. It seems the culprit is all of the older kernels still lying around on my system even though they are no longer in use. Here are the steps I took in order to remove these old kernels and reclaim my /boot partition space.

A few warnings:

  • Always understand commands you are running on your machine before you run them. Especially when they start with sudo.
  • Be very careful when removing kernels – you may end up with a system that doesn’t boot!
  • My rule of thumb is to only remove kernels older than the most recent 2 (assuming I haven’t had any bad experiences with either of them). This allows me to revert back to a slightly older version if I find something that no longer works in the latest version.
First determine what kernel your machine is actually currently running

For example running the command:

uname -a

prints out the text “4.4.0-45-generic“. This is the name of the kernel my system is currently using. I do not want to remove this one!

Next get a list of all installed kernels

You can do this a few different ways but I like using the following command:

dpkg --list | grep linux-image

This should print out a list similar to the one in the screenshot below.

Example list of installed kernels

Example list of installed kernels

From this list you can identify which ones you want to remove to clear up space. On my system I had versions 4.4.0-21.37, 4.4.0-36.55, 4.4.0-38.57 and 4.4.0-45.66 so following my rule above I want to remove both 4.4.0-21.37 and 4.4.0-36.55.

Remove the old kernels

Again this can be done a number of different ways but seeing as we’re already in the terminal why not use our trust apt-get command to do the job?

sudo apt-get purgelinux-image-4.4.0-21-generic linux-image-4.4.0-36-generic

and just like that almost 500MB of disk space is freed up!