Cleanup old kernels on Debian and/or Ubuntu

Cleanup_old_kernels_on_Debian_Ubuntu.txt

I watched one of my virtual machines perfor an apt-get dist-upgrade and I noticed abot 10 kernels being built.
This took a quite a while to complete.  Here is the solution I found that I don't want to forget.

REF: https://www.tecmint.com/remove-old-kernel-in-debian-and-ubuntu/

Show kernels installed:

   dpkg -l | grep linux-image | awk '{print$2}'
   
Install this package to do this easier:

  sudo apt install byobu
  
Here is the magic command:

  sudo purge-old-kernels --keep 3
  
Here is another way:
   REF: https://askubuntu.com/questions/2793/how-do-i-remove-old-kernel-versions-to-clean-up-the-boot-menu

      dpkg --list | grep linux-image | awk '{ print $2 }' | sort -V | sed -n '/'`uname -r`'/q;p'
      sudo apt-get -y purge <old-kernel-image-from-above>