Dear Maintainer,

After having created some systemd user units (and timers), as I have
done on several other machines without issue, I noticed that the units
were not started upon login on this particular machine. In fact
systemctl showed no knowledge of them at all - until I reloaded the
systemd user daemon and timers; after that all was fine.

The difference between this machine and the other working setups: my
home is encrypted via ecryptfs on this laptop.

So I wondered if maybe the systemd user daemon was started upon login
BEFORE my home was decrypted (thus it'd know nothing of my setup).

Sure enough, in /etc/pam.d/common-session, pam_ecryptfs.so unwrap was
invoked AFTER pam_systemd.so.

Reversing the order fixed the problem. I don't know too much about pam but
I think ecryptfs should specify a higher priority in the common-session stack.