Clean unuse kernel

1. Intro

If you have an old kernel that you are not using, you should delete it.
Because it fill up the /boot capacity.

2. How to do?

2.1. check kernel

# current kernel
uname -a

# list kernel
sudo dpkg --list | grep linux-image

2.2. Delete old kernel

sudo apt purge linux-image-[version]

2.3. check kernel

# current kernel
uname -a

# list kernel
sudo dpkg --list | grep linux-image