Avoiding repetition of service definition in Nagios Core - nagios

Question

A service definition for a host looks like:
service{
name host_1_svc
....
check_command check_xyz!abc
}
A similar check needs to be performed on host2, except that the parameter to the check_command is lmn.
So I have to define:
service{
name host_2_svc
....
check_command check_xyz!lmn
}
What is the general convenient practice to avoid having to define the service over and over again with only a minor change?
Thanks,
Yash

Answer 1

You can define a custom host variable in each of the hosts:
define host{
use generic-host
host_name host1
address 10.0.0.1
_chk_value abc
}
define host{
use generic-host
host_name host2
address 10.0.0.2
_chk_value lmn
}
define service{
use generic-service
name host_chk_svc
host_name host1,host2
check_command check_abc!$_HOSTCHK_VALUE$
}
Note the underscore before the custom variable in the host definition (this defines it as custom), and then underscore at the beginning of the macro, but not in the middle of it ($_HOSTCUSTOM$ rather than $HOST_CUSTOM$).
http://nagios.sourceforge.net/docs/3_0/customobjectvars.html

Answer 2

Define a host group, then add that host to the group and you only need to define the service once.
the relationship between hosts and host groups and services and service groups can be hard to visualise, especially if you don't have a consistent naming scheme for the files in your nagios /etc folder.
Here are two charts i've found which help make sense of it:
a slideshow about vaious network monitoring options: http://www.semintelligent.com/talks/chuug/network-monitoring/#%2827%29
a short but helpful page about Nagios setup: http://www.the-tech-tutorial.com/?p=1433