My previous systemd drop-in workaround was incomplete. This is the complete version of /etc/systemd/system/nagios4.service.d/10-fix-for-incorrect-pid-management.conf:
[Service] ExecStartPost=/bin/sh -c 'umask 022; pgrep nagios4 > /var/run/nagios4/nagios4.pid' RuntimeDirectory=nagios4 PIDFile=/run/nagios4/nagios4.pid Where RuntimeDirectory=nagios4 is required for /var/run/nagios4 to be automatically created. -- Jaime Hablutzel - +51 994690880
