I've installed "nrpe" on SLES12SP1, but I'm having an issue when I start up the
nrpe daemon:

Jun 27 12:30:11 linux-9oij nrpe[9175]: Cannot write to pidfile
'/run/nrpe/nrpe.pid' - check your privileges.

I checked and "/run/nrpe" doesn't exist. It doesn't look like the RPM created
it.

I'm not sure where the source nrpe.spec is but I looked at
https://build.opensuse.org/package/view_file/server:monitoring/nrpe/nrpe.spec?expand=1
and found this:

%if 0%{?suse_version} <= 1230
%{_sysconfdir}/init.d/nrpe
%ghost %dir %{_rundir}/%{name}
%ghost %{_rundir}/%{name}/nrpe.pid
%endif

I wasn't familiar with the %ghost directive so I read
http://www.rpm.org/max-rpm-snapshot/s1-rpm-inside-files-list-directives.html

I don't see /run/nrpe or /run/nrpe/nrpe.pid in the RPM listing... 

linux-9oij:/srv/www # rpm -ql nrpe
/etc/nrpe.cfg
/etc/nrpe.d
/etc/sysconfig/SuSEfirewall2.d/services/nrpe
/etc/xinetd.d/nrpe
/usr/lib/systemd/system/nrpe.service
/usr/lib/systemd/system/nrpe.socket
/usr/lib/systemd/system/nrpe@.service
/usr/lib/tmpfiles.d/nrpe.conf
/usr/sbin/nrpe
/usr/sbin/rcnrpe
/usr/share/doc/packages/nrpe
/usr/share/doc/packages/nrpe/README.SSL
/usr/share/doc/packages/nrpe/README.SUSE
/usr/share/doc/packages/nrpe/SECURITY
/usr/share/man/man8/nrpe.8.gz

And after I manually create /run/nrpe and restart the NRPE daemon, "/run/nrpe"
and "/run/nrpe/nrpe.pid" don't appear to be owned by nrpe:

linux-9oij:/srv/www # rpm -qf /run/nrpe/nrpe.pid
file /run/nrpe/nrpe.pid is not owned by any package
linux-9oij:/srv/www # rpm -qf /run/nrpe/
file /run/nrpe is not owned by any package

So I'm guessing my suse_version might be acting up, so I looked at the output
of "rpm --showrc | grep "suse"":

-14: suse_version       1315

According to
https://en.opensuse.org/openSUSE:Build_Service_cross_distribution_howto, 1315
is SLES 12 or openSUSE Leap 42.x

So that seems a bit nuts...

I have sysemd, so I don't need the /etc/inti.d/nrpe service, but the systemd
unit complains when it can't write to /run/nrpe/nrpe.pid. 

Of course, I'm not 100% sure why it needs the pid... I see no references in the
systemd units.

If I look in /etc/nrpe.cfg, I see the following:

# PID FILE
# The name of the file in which the NRPE daemon should write it's process ID
# number.  The file is only written if the NRPE daemon is started by the root
# user and is running in standalone mode.

pid_file=/run/nrpe/nrpe.pid

Here's what I see via ps:

nagios     9252      1  0 12:34 ?        00:00:00 /usr/sbin/nrpe -c
/etc/nrpe.cfg -d

According to http://docs.icinga.org/latest/en/nrpe.html, the other option than
"standalone mode" is to start it with xinetd, which seems to be disabled by
default with systemd...

I imagine most people would use systemd over xinetd...so I'm not sure why the
pid is being ghosted in the nrpe package.