RAW logos and Debian's update-motd.d are problematic

[rgriebl]

This took me too long to figure out, so I thought I'd at least document the problem (and solution) here:

I have fastfetch running on Debian from a script in /etc/update-motd.d/ and this worked perfectly fine on multiple machines, until it stopped displaying the generated /run/motd.dynamic on a new server I set up. If this happens to you, then check the file size of this generated motd: if it is larger than 65K, libpam_motd will silently ignore it.
The problem is that 65K isn't hard to exceed with a PNG that you convert via kitten icat to get rid of the runtime image-magick dependency.
The only solution here is to tweak your image to make sure the raw kitty image is way below 65K to leave some headroom for the actual message, as the 65K limit is hard-coded.

This should also apply to Ubuntu, as it uses the same update-motd mechanism.