nbd-server not starting from systemd on openSUSE Leap 15.2

[rparkins999]

If I try to enable nbd-server to start from systemd on openSUSE Leap 15.2, I get this

* nbd-server.service - Network Block Device server
   Loaded: loaded (/usr/lib/systemd/system/nbd-server.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Sun 2021-05-23 18:50:30 BST; 2min 22s ago
     Docs: man:nbd-server(1)
           man:nbd-server(5)
  Process: 1338 ExecStart=/usr/bin/nbd-server $OPTIONS (code=exited, status=0/SUCCESS)
 Main PID: 1344 (code=exited, status=1/FAILURE)

May 23 18:50:30 localhost systemd[1]: Starting Network Block Device server...
May 23 18:50:30 localhost systemd[1]: nbd-server.service: PID file /run/nbd-server.pid not readable (yet?) after start: No such file or directory
May 23 18:50:30 localhost systemd[1]: Started Network Block Device server.
May 23 18:50:30 localhost systemd[1]: nbd-server.service: Main process exited, code=exited, status=1/FAILURE
May 23 18:50:30 localhost systemd[1]: nbd-server.service: Unit entered failed state.
May 23 18:50:30 localhost systemd[1]: nbd-server.service: Failed with result 'exit-code'.

if I remove the line

PIDFile=/run/nbd-server.pid

from /usr/lib/systemd/system/nbd-server.service, it still fails, but without the message that it couldn't find the PID file.

It looks as if it is getting started too soon, before something that it depends on, but the error message isn't very helpful as to what.

If I put something like this

#!/bin/sh
logger starting boot.local
(
  sleep 60;
  logger boot.local starting nbd-server
  nbd-server 2>1 | logger
  logger boot.local done starting nbd-server
) &

into /etc/init.d/boot.local (and make it executable), it starts up nbd-server successfully.