Apache webserver cannot access nagios logfiles


just wanted to share my experiences with that problem. Archive logs had permissions for nagios user and group adm. Here it was sufficient to just change the group to www-data. But that was not enough for the logfile /var/log/nagios/nagios.log. It changed nearly instantly back to nagios:nagios with 640 permissions.
I solved it with adding www-data user to group nagios but that seems an odd workaround for me.