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setevoy
Asked: 2015-07-22 02:26:30 +0800 CST

Nagios: Could not resolve hostname

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My setup:

hosts.cfg - contains definitions for each host under monitoring, e.g.:

define host{
        use                     linux-server
        host_name               rdss-vpn
        display_name            VPN
        address                 54.***.***.176
        }

hosts_groups.cfg - define groups:

define hostgroup{
        hostgroup_name   rdss-service-server
        alias            RDSS services
        members          [...],  rdss-vpn
        }

services.cfg:

define service{
        use                             local-service
        hostgroup_name                  rdss-web-server, rdss-service-server
        service_description             Memory usage
        check_command                   check_linux_memory!50!80
        notifications_enabled           1
        }

And check_linux_memory in commands.cfg:

define command{
        command_name    check_linux_memory
        command_line    $USER1$/check_nrpe -H $HOSTNAME$ -c check_linux_memory -a '-f -w $ARG1$ -c $ARG2$'
        }

Here is example of host, where check_linux_memory works:

define host{
        use                     linux-server
        host_name               www.dev.domain.com
        display_name            DEV
        address                 54.***.***.136
        }

It's group:

define hostgroup{
        hostgroup_name   rdss-web-server
        alias            RDSS web servers
        members          www.dev.domain.com, www.qa.domain.com, www.staging.domain.com
        }

Problem is with few new added hosts, like rdss-vpn - Nagios won't get it's IP from hosts (please note - I have few other servers (also in groups) in check_linux_memory - all works).

Instead - I have an error in nagios.log:

[1437473407] SERVICE ALERT: rdss-vpn;Memory usage;WARNING;HARD;4;(No output on stdout) stderr: Could not resolve hostname rdss-vpn: Name or service not known

nagios

1 Answers

  1. Best Answer

    Your problem is that you wrote your check command to use $HOSTNAME$ instead of $HOSTADDRESS$.

    This happens to work for your other hosts, because they are named with FQDNs (e.g., www.dev.domain.com). It doesn't work for rdss-vpn because that's not a valid hostname from the perspective of your Nagios box.

    You should use the address, not the hostname, in checks. This removes DNS as a dependency for Nagios checks. If you really need to use a hostname instead of the IP, put the hostname in as the host address.

    Also, traditionally one would just pass the check to check_nrpe as an ARG, like check_nrpe!check_memory or check_nrpe!check_memory!50 80. But it's up to you, ultimately.

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