#TIL : Cleaning up old linux kernels

Last day, I try to reboot a production server which has out-of-space /boot (I upgraded many kernels without rebooting, so system doesn't clean up old ones). And in the end, doom day had come ! It installed new kernel failed and booting to that kernel. My system crashed !

So, I learned from it :

• Never ever upgrade kernel without cleaning up old ones (just reboot)
• Never ever reboot a production without backup
• MORE IMPORTANT, NEVER do 2 above things at same time in the weekend !!!

Solution :

• Check current kernel : uname -r

• List all kernels : dpkg --list | grep linux-image

• Remove a kernel : sudo apt-get purge linux-image-x.x.x-x-generic

• Finally, update grub after removing all old kernels : sudo update-grub2

• YOLO command for DEBIAN distros (to remove all of old kernels in 1 line), from AskUbuntu

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

THEN, sudo reboot