NTP checks with icinga2

On my new Icinga2 monitoring host, I am slowly adding additional service checks to achieve parity with my existing Nagios monitoring. Next on my list, implementing NTP checks. The first step was to add a new service check to the Icinga2 configuration:

/etc/icinga2/conf.d/services.cfg:

apply Service "ntp_time" {
  import "generic-service"
  check_command = "ntp_time"
  assign where host.vars.os == "Linux"
}

The service check produced an error, as seen in the icingaweb2 interface:

execvpe(/usr/lib64/nagios/plugins/check_ntp_time) failed: No such file or directory

Oh! I don’t have the appropriate Nagios plugin installed on the Icinga2 host.

sudo yum install nagios-plugins-ntp

The NTP service check now reports OK on some hosts, but on other hosts I get a different error:

CRITICAL: No response from NTP server

The hosts that did not receive a response are all using chronyd. I edited /etc/chrony.conf and added:

allow 192.168.46.46

And restarted chronyd:

systemctl restart chronyd

Now all but one host reports OK. The last remaining host to show an error? The Icinga2 host itself!

allow 127.0.0.1

Another chronyd restart, and the NTP service on all hosts reports OK.