Nagios Support Forum

Posted: **Fri Apr 20, 2018 9:59 pm**

Below is the sample config I am using to try to monitor a web site. From all my reading I have done, I think this is the right way, however, when verifying the config file (websites.cfg) it doesn't like the check_http -H in the file. I am using Nagios Core 4.1.1. Any help would be appreciated.

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define host{
        use generic-host                ;Inherit default values from a template
        host_name website         ; The name we're giving to this host
        alias http://www.website.com             ; A longer name associated with the host
        address http://www.website.com           ; IP address of the host
         max_check_attempts 3
        contact_groups          admins
        #hostgroups allhosts            ; Host groups this host is associated with
        }

define service{
        use generic-service ; Name of service template to use
        host_name website
        service_description PING
        check_command check_ping!100.0,20%!500.0,60%
        }

define service{
        use generic-service             ; Name of service template to use
        host_name website
        service_description HTTP
        check_command check_http -H http://www.website.com
        notifications_enabled 0
        }

Posted: **Sat Apr 21, 2018 4:48 pm**

We would need to see your command definition for the check_http command to say whether or not this syntax is correct. Remember, the check_command directive of your service definitions references a command definition; Not an actual plugin.

What I suspect is happening is your check_http command definition is already accounting for the host's name via either the -I or -H flag of the check_http plugin. Here's the default command definition (installed via the make install-config step of the official installation documentation) for the check_http command:

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# 'check_http' command definition
define command{
        command_name    check_http
        command_line    $USER1$/check_http -H $HOSTADDRESS$ $ARG1$
        }

Where the $HOSTADDRESS$ macro is inherited from the service definition's parent host definition. Using the example host/service definitions you provided compared against the default check_http command definition:

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define host{
        use generic-host                ;Inherit default values from a template
        host_name website         ; The name we're giving to this host
        alias http://www.website.com             ; A longer name associated with the host
        address http://www.website.com           ; IP address of the host
         max_check_attempts 3
        contact_groups          admins
        #hostgroups allhosts            ; Host groups this host is associated with
        }
define service{
        use generic-service             ; Name of service template to use
        host_name website
        service_description HTTP
        check_command check_http -H http://www.website.com
        notifications_enabled 0
        }

If your command definition for check_http looks like mine, you're essentially passing the -H argument twice: Once via your command definition, then once again via your service definition's check_command directive. Using the above configuration, the actual command that is executed from the command-line would resolve to something like this:

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/path/to/check_http -H http://www.website.com -H http://www.website.com

Posted: **Sat Apr 21, 2018 5:29 pm**

Here is the check_http part of my command.cfg file.

# 'check_http' command definition
define command{
command_name check_http
command_line $USER1$/check_http -I $HOSTADDRESS$ $ARG1$
}

Posted: **Sat Apr 21, 2018 8:41 pm**

One of the reasons why I am messing around with the check_http configuration is because when the site in question goes down Nagios still thinks it's online. So I thought maybe the default website was responding because the actual website is down.

Posted: **Sat Apr 21, 2018 9:37 pm**

I just denied access to the default website of my apache server and all my URL's that I am monitoring seem to be going to that site. This leads me to believe that the host headers aren't getting there via Nagios maybe? the sites work fine in a browser. What am I missing? Sorry for so many posts. I am new to this forum and I am still waiting for a couple posts to be approved.

Posted: **Mon Apr 23, 2018 3:29 pm**

Your missing the ! Exclamation point in the check command which is used to delineate the arguments for the checks and you also do not need the http:// in the command for the -I and the -H options for the command. The check_http plugin will fill it in for you.

Edit your service check and change this from

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check_command check_http -H http://www.website.com

to

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check_command check_http!-H www.website.com

Then edit the host check and change this from

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address http://www.website.com           ; IP address of the host

to

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address www.website.com           ; IP address of the host

Save the changes and restart nagios and it should work for you.
If you get any errors, please post them here. Thanks.

https://assets.nagios.com/downloads/nag ... n/toc.html
https://assets.nagios.com/downloads/nag ... vices.html

Posted: **Mon Apr 23, 2018 3:56 pm**

That worked!! Thank you so much!

Posted: **Mon Apr 23, 2018 4:34 pm**

Your welcome. Glad to help. I'll mark the post as solved and lock it. Feel free to open a new post for any other questions in the future.

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