Elementary OS - Not enough free disk space (on disk '/boot') for Software Update

When you run Software Updater, you receive the following error:

You will find that even you follow the instruction to empty your trash and remove temporary package of fome installations using 'sudo apt-get clean' also cannot fix the problem.


It is because there are so many old kernel have been installed.

When you run "uname -r", you will see the running kernal version (3.19.0-39-generic) and then, run the "dpkg --get-selections|grep linux-image", you will find there are many different version kernel..


Solution:
Remove the old kernal files by using the following command:
sudo apt-get purge linux-image-x.xx.x-xx-generic linux-image-extra-x.xx.x-xx-generic



Re-run the above command until you leave the current running kernel like the following:

Then, reboot the machine.

After logon the machine again, run the software updater, it will able to update now.


Reference:
http://david50.pixnet.net/blog/post/38158207-%5B%E7%AD%86%E8%A8%98%5Dubuntu%E4%B8%AD%E6%B8%85%E9%99%A4-boot%E4%B8%AD%E4%B9%8B%E8%88%8A%E7%89%88kernel

Elementary OS - Not enough free disk space (on disk '/boot') for Software Update