Comment # 27 on bug 1013200 from Patrick Schaaf

Rebooted some more this morning...

On the suspicion that there would be some timing problem between sddm, X, and
sddm-greeter startup, I wrapped sddm-greeter with a shellscript, and then used
that to log some environmental and process list stuff, as well as introduce
some delay.

The logged argument and environment information was inconspicuous between the
nonworking after-boot run and the subsequent working run when manually
restarting the display-manager unit.

Sleeping for some seconds before really starting sddm-greeter, did NOT help.
So, it's not simply a timing issue between sddm starting X, and starting the
greeter.

But, comparing the logged process lists between the after-boot (does not work)
scenario, and a subsequent working run (systemctl restart display-manager), I
got a suspicion.... I noticed that sddm (and X) were started rather early,
immediately after wickedd came up, but BEFORE systemd-logind.

On that suspicion, I added an After= dependency on systemd-logind to the
display-manager.service unit - and that GOT IT TO WORK!

Not I don't really know what I'm doing here :) ..... but I hope that might help
you understand the issue better.