While upgrading from 14.04 to 16.04, my /boot partition filled & the upgrade failed. I now lack a /boot/initrd.img-4.4.0-119-generic, which the upgrade was trying to create when it failed.
The system booted anyway. I'm afraid to reboot as things stand. /initrd.img points to /boot/initrd.img-4.4.0-119-generic, which doesn't exist.
What to do?