Removing old kernels on Ubuntu.

On Linux distributions you get kernel update and the images of old kernels remain on your machine occupying space. I got a kernel update today:

$ uname -r
4.4.0-28-generic

After restart I could see that the image of old kernel was present on the machine:

$ dpkg -l | tail -n +6 | grep -E 'linux-image-[0-9]+' | grep -Fv $(uname -r)
ii  linux-image-4.4.0-24-generic                4.4.0-24.43                                         amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP

I removed the old kernel by using following commands one by one:

sudo dpkg --purge linux-signed-image-4.4.0-24-generic
sudo dpkg --purge linux-image-extra-4.4.0-24-generic
sudo dpkg --purge linux-image-4.4.0-24-generic

I removed the kernel headers by using following commands one by one:

sudo dpkg --purge linux-headers-4.4.0-24-generic
sudo dpkg --purge linux-headers-4.4.0-24

Since I remove the previous image on every kernel update I had to remove only 4.4.0-24 but if you are doing it first time you may have many images starting from 4.4.0.21