I’ve upgraded my Ubuntu recently and i just leave all my old kernels in my machine. Long list of kernels in the GRUB list during boot up of course. :p Although you can use Ailurus to manage all these, i came across this quick method on how to remove all kernels except the current kernel in one go.
Open your terminal CTRL+ALT+T and paste this command:
dpkg -l ‘linux-*’ | sed ‘/^ii/!d;/'”$(uname -r | sed “s/\(.*\)-\([^0-9]\+\)/\1/”)”‘/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d’ | xargs sudo apt-get -y purge
Wait until DONE.
Restart your machine and see your updated GRUB list. Clean!
Thanks Ubuntu Genius!