Posts tagged Nagios 3

Custom macros in host definitions

Aug 16th

Posted by Christian in Life

Well, I was playing with the hostgroup inheritance earlier. One problem with that is, if you define a duplicate service Nagios is really unpredictable or rather inconsistent. Now, as Thomas Guyot-Sionnest told me, I should try custom macros for the check definition. So what I did was the following:

templates/host-windows.cfg

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define host {
  name         generic-windows
  register     0
  _RDPPORT     3389
}

hostgroups/windows.cfg

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define hostgroup {
  hostgroup_name          windows
  alias                   Windows Servers
  hostgroup_members       windows-terminal
}
 
define service {
  use                     generic-service
  check_command           check_tcp!$_HOSTRDPPORT$
  service_description     RDP
  hostgroup_name          windows
}

hosts/terminal1.cfg

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define host {
  use                   generic-windows
  host_name             terminal1
  alias                 terminal1.barfoo.org
  address               10.0.0.250
  parents               barfoo-home
  hostgroups            windows-terminal
  _RDPPORT              3390
}

As you can see, the default RDP port is 3389 (as defined in the host template), but for some systems you might want to “change” the port (for example, if you’re having a citrix farm and you changed the RDP port to something else and still want to be able to check whether or not the RDP service is active), thus the check using the macro, and a single host redefining the macro, thus having a bit more flexibility.

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Nagios 3 and hostgroup inheritance

Aug 8th

Posted by Christian in Life

1 comment

As I wrote some time ago, I was trying to utilize Nagios 3.x’s neat feature of “nested” hostgroups. Well, as it turned out I thought it worked differently; basically like this:

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define hostgroup {
        hostgroup_name      a-parent-hostgroup
        alias               Our toplevel parent hostgroup
}
 
define service {
       use                  generic-service
       check_command        check_dummy!0!
       service_description  SSH
       hostgroup_name       a-parent-hostgroup
}
 
define hostgroup {
        hostgroup_name      a-child-hostgroup
        hostgroup_members   a-parent-hostgroup
        alias               Our child hostgroup
}
 
define service {
       use                  generic-service
       check_command        check_dummy!0!
       service_description  LOAD
       hostgroup_name       a-child-hostgroup
}

As you can cleary see on line 14, I thought you define the relation between two hostgroups in the child hostgroup. The problem with it was basically (as I said in the earlier posts), that all the services defined for the child hostgroups are handed on upwards to the parent hostgroup(s).

But after talking to Tobi, I quickly found out, that the relation is in fact defined within the parent hostgroup. So if you simply put hostgroup_members within the parent hostgroup and define all child hostgroups which should inherit from the parent one, you should be just fine.

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