Error updating Debian Testing

I got the following error messages while updating Debian Testing this morning:

E: initramfs-tools: installed initramfs-tools package post-installation script subprocess returned error exit status 1


gzip: stdout: No space left on device
E: mkinitramfs failure gzip 1
update-initramfs: failed for /boot/initrd.img-5.14.0-4-amd64 with 1.
dpkg: error processing package initramfs-tools (--configure):
 installed initramfs-tools package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 initramfs-tools

Say What? This is a 500G HD and it's only 7% full!

Turns out /boot is on its own 500MB partition and its full.

I had too many old kernels installed, and the solution was to get rid of most of them (keeping one known good backup kernel).

I searched for "linux-image" in Synaptic, but this can be done from a command line too obviously.

When I had finished I ran

# update-initramfs -u

Which is the part of the update precess that had failed.

I will have to pay more attention to housekeeping from now on.