Support forum for Nagios Core, Nagios Plugins, NCPA, NRPE, NSCA, NDOUtils and more. Engage with the community of users including those using the open source solutions.
Try running the plugin as the root user and see if it works.
If it does, the plugin needs to have the superuser bit set to run so login as root and run the following to set it.
Another reason for the plugin to fail is most likely it's because your system is starved of file-descriptors. You could try either upping the ulimit -n value of Nagios or use check_icmp instead. check_icmp uses a single socket rather than a pipe (two file-descriptors fewer per check). It's also a lot faster, so resources aren't hogged so long.
Be sure to check out our Knowledgebase for helpful articles and solutions!