After rebooting the VM now, sshd died even when there was hundreds of megabytes free RAM available. So it seems I spoke too soon when I said it seemed to be for that reason.

Previously I haven't seen much detailed reason for why it dies in system messages. But this time it said something very specific:

> sshd[2036]: fatal: pack_hostkeys: serialize hostkey private: string is too large

Which kind of sounds like one of the sshd hostkey files might be corrupt? And maybe it only triggers after a while becuase it happens when scanners try to connect to it and during ssh negotiation sshd ends up selecting a different hostkey type than the one it uses when I connect to the machine myself?

I'm going to regenerate all of the three hostkey files on the server, and after that also disable the two that I can do without anyway.