Logging in to one of my servers was irritatingly slow, so I decided to fix it. Instead of logging in with ssh, I used ssh -vvv which gives lots of information about what's going on. None of it helped.
Then I noticed that it wasn't only slow when I logged in with ssh, it was also slow when I was already logged in, and wanted to change the user with "su". Which means that it isn't an ssh issue, it's an authentication issue.
So I logged in using su, and had a good look at the syslog (/var/log/messages).
Aug 30 01:37:02 volds dbus: [system] Activating via systemd: service name='net.reactivated.Fprint' unit='fprintd.service'
Aug 30 01:37:02 volds systemd: Starting Fingerprint Authentication Daemon...
Aug 30 01:37:02 volds dbus: [system] Successfully activated service 'net.reactivated.Fprint'
Aug 30 01:37:02 volds systemd: Started Fingerprint Authentication Daemon.
It's trying to check my fingerprint! And I don't even have a fingerprint reader. Where did that come from?
So I stopped it with "systemctl stop fprintd.service", and now logging in is instant.
But I don't want it to happen each time I start up the computer, so I disabled it with
"systemctl disable fprintd.service"