Combined nagios nrpe check for dual (ntp) servers

Here is quick hint if you want to use nagios/nrpe to have a system test if it can reach either one of two (ntp) servers. Use the bash || operator in the nrpe.cfg command to combine two plugins:

command[check_ntp]=/usr/lib64/nagios/plugins/check_ntp_time -H ntp1 -w 0.5 -c 1 || /usr/lib64/nagios/plugins/check_ntp_time -H ntp2 -w 0.5 -c 1

The second command will only be executed if the first one ends with a non-zero exit code. If the second check succeeds, it will return an OK status. If it fails as well, the check will go into WARNING or CRITICAL.
You could obviously also use the same technique for other checks than check_ntp, but make sure that a timeout of the first command is not so high that check_nrpe times out itself before the second one is run.