Linux Networking Cookbook

13.8. Speed Up Nagios with check_icmp

Problem

You've seen on some Nagios forums or mailing lists that you should use the check_icmp plug-in instead of check_ping because it is faster and more efficient. So, you've tried it, but it doesn't work; you get a check_icmp: Failed to obtain ICMP socket: Operation not permitted error. This doesn't seem like an improvement—now what?

Solution

The check_icmp plug-in needs root permissions to work, so you need to set the SUID bit to allow unprivileged users to run it with root privileges.

First, replace all instances of check_ping in your configuration files with check_icmp. Use the grep command to find them:

	# grep -r check_ping /usr/local/nagios/etc/

Then, set the SUID bit on check_icmp, and make it a member of the nagios group:

	# cd /usr/local/nagios/libexec
	# chown root:nagios check_icmp
	# chmod 4711 check_icmp

Now, it will work without complaints.

Discussion

check_ping calls the external /bin/ping, while check_icmp is an internal Nagios command. Nagios uses ICMP echo request and ICMP echo reply a lot, so this adds up to a nice performance enhancement.

See Also

• The FAQ in the nagios-plugins source tree, plus the README and REQUIREMENTS

• Chapter 8, "Managing Users and Groups," in Linux Cookbook, by Carla Schroder (O'Reilly)