See what all linux images/kernels are present in your system
dpkg -l linux-image-\* | grep ^ii
Now see what all linux kernels you can remove
kernelver=$(uname -r | sed -r 's/-[a-z]+//')
mongoexample$ dpkg -l linux-{image,headers}-"[0-9]*" | awk '/ii/{print $2}' | grep -ve $kernelver
Now remove the linux kernels
sudo apt-get purge linux-image-4.4.0-70-generic
