If you're tired to see lots of kernel in your linux system like me, you're in the right place to remove them safely :) At first, you have to install byobu package for your distubution. I use Linux Mint so for me;
sudo apt-get install byobu
After you install byobu package, purge-old-kernels command will be ready for use. Then run;
This command will be purge old kernels but keeps at least latest 2 kernels by default.