Procedure 3.1. Monitoring a Remote HTTP Service with Nagios

1. Create a directory inside /etc/nagios/objects using mkdir. You can use any desired name for it.

2. Open /etc/nagios/nagios.conf and set cfg_dir (configuration directory) to the directory you have created in the first step.

3. Change to the configuration directory created in the first step and create the following files: hosts.cfg, services.cfg and contacts.cfg

4. Insert a host object in hosts.cfg:

   define host {
    name                   host.name.com
    host_name              host.name.com
    address                192.168.0.1
    use                    generic-host
    check_period           24x7
    check_interval         5
    retry_interval         1
    max_check_attempts     10
    contact_groups         admins
    notification_interval  60
    notification_options   d,u,r
   }                        
                           

5. Insert a service object in services.cfg:

   define service {
    use                    generic-service
    host_name              host.name.com
    service_description    HTTP
    contact_groups         router-admins
    check_command          check_http
   }
                   

6. Insert a contact and contactgroup object in contacts.cfg:

   define contact {
    contact_name           max-mustermann
    use                    generic-contact
    alias                  Webserver Administrator
    email                  mmustermann@localhost
   }
   
   define contactgroup {
    contactgroup_name      admins
    alias                  Administrators
    members                max-mustermann
   }
                       

7. Execute rcnagios restart to (re)start Nagios.

8. Execute cat /var/log/nagios/nagios.log and verify whether the following content appears:

    [1242115343] Nagios 3.0.6 starting... (PID=10915)
    [1242115343] Local time is Tue May 12 10:02:23 CEST 2009
    [1242115343] LOG VERSION: 2.0
    [1242115343] Finished daemonizing... (New PID=10916)

Procedure 3.2. Monitoring a Remote Host Resource with Nagios (Server)

1. Install nagios-nsca (for example, zypper in nagios-nsca).

2. Set the following options in /etc/nagios/nagios.cfg:

   check_external_commands=1
    accept_passive_service_checks=1
    accept_passive_host_checks=1
    command_file=/var/spool/nagios/nagios.cmd

3. Set the command_file option in /etc/nagios/nsca.conf to the same file defined in /etc/nagios/nagios.conf.

4. Add another host and service object:

   define host {
    name                            foobar
    host_name                       foobar
    address                         10.10.4.234
    use                             generic-host
    check_period                    24x7
    check_interval                  0
    retry_interval                  1
    max_check_attempts              1
    active_checks_enabled           0
    passive_checks_enabled          1
    contact_groups                  router-admins
    notification_interval           60
    notification_options            d,u,r
   }

   define service {
    use                             generic-service
    host_name                       foobar
    service_description             diskcheck
    active_checks_enabled           0
    passive_checks_enabled          1
    contact_groups                  router-admins
    check_command                   check_ping
   }

5. Execute rcnagios restart and rcnsca restart.

Procedure 3.3. Monitoring a Remote Host Resource with Nagios (client)

1. Install nagios-nsca-client on the host you want to monitor.

2. Write your test scripts (for example a script that checks the disk usage) like this:

   #!/bin/bash
                           
    NAGIOS_SERVER=10.10.4.166
    THIS_HOST=foobar
                           
    #
    # Write own test algorithm here
    #
                        
    # Execute On SUCCESS:
    echo "$THIS_HOST;diskcheck;0;OK: test ok" \
             | send_nsca -H $NAGIOS_SERVER -p 5667 -c /etc/nagios/send_nsca.cfg -d ";"
                           
    # Execute On Warning:
    echo "$THIS_HOST;diskcheck;1;Warning: test warning"  \
             | send_nsca -H $NAGIOS_SERVER -p 5667 -c /etc/nagios/send_nsca.cfg -d ";"
                           
    # Execute On FAILURE:
    echo "$THIS_HOST;diskcheck;2;CRITICAL: test critical"  \
             | send_nsca -H $NAGIOS_SERVER -p 5667 -c /etc/nagios/send_nsca.cfg -d ";"

3. Insert a new cron entry with crontab -e. A typical cron entry could look like this:

   */5 * * * * /directory/to/check/program/check_diskusage