Ah we did hit that kernel/initramfs issue with /boot getting filled up by Ubuntu already before. If it is 100% full even the autoremove fails. Would be good to actually not just maybe warn about that, but see how the whole situation can be mitigated in the first place. Afterall it is not much use to have that many kernel versions around.

@girish & @marcusquinn thanks for the hints! Finally the AWS guide did the trick, it was a 2 step approach (in my case): sudo growpart /dev/sda 3 sudo resize2fs /dev/sda3