clean up ubuntu kernels

remove-kernels.md

/boot full of garbage kernels

This discussion

https://askubuntu.com/questions/345588/what-is-the-safest-way-to-clean-up-boot-partition

has this answer:

https://askubuntu.com/a/809977

apt install -y byobu
purge-old-kernels -y --keep 1
apt-get -y autoremove --purge

butttt if there is too little space left you will still have to very carefully remove old kernels manually ...

# check current kernel
uname -r
# then rm /boot/<unused-crap-kernel-stuff>
# follow instructions above
# purge-old-kernels -y --keep 1
# ...