While Nagios executes the check, do you see a connection on your Mac ? Is anything written in the syslog on your Mac? Something seems to be strange about your output: /usr/lib/nagios/plugins/check_nrpe -H mac.my.domain -c check_users USERS OK - 3 users currently logged in |users=0;5;10;0 Take a look at the perfdata, it shows 0 users while the output shows 3 users. Is that a copy+paste error or is this the actual result when you launch the check on the command line? <div class="gmail_quote">On Thu, Jan 26, 2012 at 5:37 PM, John Stile <<a href="mailto:john@stilen.com">john@stilen.com</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> Recently I tried to setup nrpe monitoring of an osx system by installing nagios-plugins-1.4.15.tar.gz and nrpe-2.12.tar.gz on osx 10.5, and locally everything works fine. This works: /usr/local/nagios/libexec/check_nrpe -H localhost -c check_users USERS OK - 3 users currently logged in |users=3;5;10;0 Next I tried to configure my nagios server (debian sarge with packaged nagios 1.3-cvs), and from the server command line, this works: /usr/lib/nagios/plugins/check_nrpe -H mac.my.domain -c check_users USERS OK - 3 users currently logged in |users=0;5;10;0 The problem is adding the monitor to /etc/nagios/services.cfg define service{ use generic-service host_name mac.my.domain service_description Users is_volatile 0 check_period 24x7 max_check_attempts 3 normal_check_interval 5 retry_check_interval 1 contact_groups linux-admins notification_interval 120 notification_period 24x7 notification_options w,u,c,r check_command check_nrpe!check_users } Results in web interface shows: Status: UNKNOWN Status Information: (No output returned from plugin) All other nrpe hosts are monitoring well. I have no other osx nrpe monitored machines as a reference. Can anyone offer some ideas (other than upgrade)? ------------------------------------------------------------------------------ Keep Your Developer Skills Current with LearnDevNow! The most comprehensive online learning library for Microsoft developers is just $99.99! Visual Studio, SharePoint, SQL - plus HTML5, CSS3, MVC3, Metro Style Apps, more. Free future releases when you subscribe now! <a href="http://p.sf.net/sfu/learndevnow-d2d" target="_blank">http://p.sf.net/sfu/learndevnow-d2d</a> _______________________________________________ Nagios-users mailing list <a href="mailto:Nagios-users@lists.sourceforge.net">Nagios-users@lists.sourceforge.net</a> <a href="https://lists.sourceforge.net/lists/listinfo/nagios-users" target="_blank">https://lists.sourceforge.net/lists/listinfo/nagios-users</a> ::: Please include Nagios version, plugin version (-v) and OS when reporting any issue. ::: Messages without supporting info will risk being sent to /dev/null </blockquote></div>