What Is A kernel and how do I remove unused Kernels? [duplicate]

I have ubuntu 12.04 lts. I am new to ubuntu and i get this warning that 0 bytes are remaining on the volume /boot. i asked a question :This is the link to it

So I Got replies saying i should remove unused kernels. Can anyone explain to me in simple language what is a kernel and how do i remove unused kernels.

Thank you :)

Solution 1:

From wikipedia

The Linux kernel is the operating system kernel used by the Linux family of Unix-like operating systems. It is a prominent example of free and open source software. The Linux kernel is released under the GNU General Public License version 2, and is developed by contributors worldwide

It is the heart of linux and any linux distribution is depend on it

while ubuntu is being updated every day. The linux kernel is also updated. So you have a couple of old archived kernels in your boot partition and you can safely remove them using this command:

sudo apt-get purge $(dpkg -l linux-{image,headers}-"[0-9]*" | awk '/ii/{print $2}' | grep -ve "$(uname -r | sed -r 's/-[a-z]+//')")