So I had an issue today in which I kept getting an error message when I attempted to upgrade my ubuntu server, it basically said I was out of disk space, which was odd as I had a 2TB drive as this is a Plex server, after running df -h I quickly noticed that /boot was @ 100% full, so after a quick Google I found the below solution. If /boot is 100% full you will not be able to just run ‘sudo apt-get autoremove’ you’ll receive a bunch of error messages, so you will have to manually delete some files.