I had a strange error after updating "systemd" on one of my Opensuse server systems from version 228.41.1 to version 228.44.1. This update seems harmless, but it is not. With it substantial changes appear in the file /usr/lib/tmpfiles.d/systemd.conf. Especially the lines:
d /run/systemd/netif 0755 systemd-network systemd-network - d /run/systemd/netif/links 0755 systemd-network systemd-network - d /run/systemd/netif/leases 0755 systemd-network systemd-network - </p>
In my case this lead to trouble - service "systemd-tmpfiles-setup.service" started to fail :
# systemctl status -l systemd-tmpfiles-setup ● systemd-tmpfiles-setup.service - Create Volatile Files and Directories Loaded: loaded (/lib/systemd/system/systemd-tmpfiles-setup.service; static) Active: failed (Result: exit-code) ..... ... ... Mar 12 11:33:32 myserv systemd-tmpfiles: [/usr/lib/tmpfiles.d/systemd.conf:19] Unknown user 'systemd-network'.
I checked whether user "systemd-network" existed with YaST. Yes, it was there - with all its default details.
However the command
getent passwd systemd-network
did not give me anything!
It took me a bit to find out what had happened. On this server I had once experimented with NIS, NISplus. The "/etc/passwd"-file still contained a line
The "/etc/group"-file had a corresponding "+:::". However, no active NIS server is any longer defined. Should not matter as long as the file have a correct format, i.e. as long as the NIS-lines are placed at the bottom of the files ...
At some point in time (?) systemd had created the user "systemd-network" and a corresponding group. Unfortunately, both entries were dumbly added at the end of the files "/etc/passwd" and "/etc/group" - i.e. after the already existing NIS-lines.
systemd-timesync:x:478:478:systemd Time Synchronization:/:/sbin/nologin +:::::: systemd-network:x:475:475:systemd Network Management:/:/sbin/nologin
Not funny! Because, this in turn became the cause for the empty "getent"-answer!
However, it seems that systemd now uses "getent" to check the existence of some special systemd-users like "systemd-network" as a requirement for starting certain services. Which then leads to errors ...
"systemd" seems to add new user- and group-entries at the bottom of the files "/etc/passwd" and "/etc/group" - without checking for NIS lines. Or it at least did at some point in the past. This may prevent the start of some initial services for which the existence of user or group entries are checked.
So, if you run across a similar problem check your "passwd" and "group" files for wrong entries at the end of the file! Move the NIS lines to the very bottom of the files. Afterward "getent" will work again for all user entries - and your failed services hopefully will start again.
Note: If you still get errors for "unknown systemd-users" you have to check whether entries for all the required users really exist in "/etc/passwd".
P.S.: The stupid thing on Opensuse is that YaST shows you the required users with passwd-entries below a NIS line as existing, whereas "getent" does not.