Monitor ssh on non-default port with Nagios

Question

I just deployed Nagios on a Gentoo server and everything is fine except ssh, which it marks as "CRITICAL" because it's refusing connections. But that's because it's running on a port different from the default 22. How do I change it so that it monitors the right port?

Answer 1

host:~$ /usr/lib/nagios/plugins/check_ssh --help
check_ssh v1991 (nagios-plugins 1.4.12)
Copyright (c) 1999 Remi Paulmier <remi@sinfomic.fr>
Copyright (c) 2000-2007 Nagios Plugin Development Team
        <nagiosplug-devel@lists.sourceforge.net>

Try to connect to an SSH server at specified server and port


Usage:check_ssh [-46] [-t <timeout>] [-r <remote version>] [-p <port>] <host>

does this answer your question? -p parameter lets you specify the port, make custom check in /etc/nagios/nrpe.cfg and put there:

command[check_remote_ssh]= /usr/lib/nagios/plugins/check_ssh -p 1234 some.host

Answer 2

In ssh pluging config /etc/nagios-plugins/config/ssh.cfg, there an alias named check_ssh_port. if it not existe you may defined like above:

$ cat >> /etc/nagios-plugins/config/ssh.cfg
define command{
        command_name    check_ssh_port
        command_line    /usr/lib/nagios/plugins/check_ssh -p '$ARG1$' '$HOSTADDRESS$'
        }

in the service file /etc/nagios3/conf.d/services_nagios2.cfg, define you ssh service to monitor like this:

define service {
        hostgroup_name                  ssh2-servers
        service_description             SSH2
        check_command                   check_ssh_port!12000!server
        use                             generic-service
        notification_interval           240 ; set > 0 if you want to be renotified
}

replace 12000 by you default ssh port and server by your target.

Answer 3

What about exceptions? Does this cover it? Only one of my servers is running sshd on a non-standard port. Should I take this one server out of the ssh_servers hostgroup?