Agenda: exercises-nagios2.txt

Nagios Installation and Configuration


PART V
Create More Host Groups
-----------------------------------------------------------------------------

0. In the web view, look at the pages "Hostgroup Overview", "Hostgroup
   Summary", "Hostgroup Grid". This gives a convenient way to group together
   hosts which are related (e.g. in the same site, serving the same purpose).

1. Update /etc/nagios3/conf.d/hostgroups_nagios2.cfg

    - For the following exercises it will be very useful if we have created
      or update the following hostgroups:

      debian-servers
      routers
      switches
 
      If you edit the file /etc/nagios3/conf.d/hostgroups_nagios2.cfg you
      will see an entry for debian-servers that just contains localhost. 
      Update this entry to include all the classroom PCs, including the
      noc (this assumes that you created a "noc" entry in your pcs.cfg
      file). Remember to skip your PC entry as it is represented by the
      localhost entry.

    # editor /etc/nagios3/conf.d/hostgroups_nagios2.cfg

     Update the entry that says:


# A list of your Debian GNU/Linux servers
define hostgroup {
        hostgroup_name  debian-servers
                alias           Debian GNU/Linux Servers
                members         localhost
        }
      
      So that the "members" parameter contains something like this. Use your
      classroom network diagram if in doubt.

                members         localhost,pc1,pc2,pc3,pc4,pc5,pc6

                Remember to replace the pc1 -- 6 with the pcs on your table.

        Be sure that the line wraps and is not on two separate lines. Otherwise
        you will get an error when you go to restart Nagios. Remember that
        your own PC is "localhost".

      - Once you have done this, add in two more host groups, one for routers and 
        one for switches. Call these entries "routers" and "switches".

      - When you are done be sure to verify your work and restart Nagios.

      - Remember to skip your pc entry as it is represented by the localhost entry.
  
2. Go back to the web interface and look at your new hostgroups


PART VI
Create Service Groups
-----------------------------------------------------------------------------

1. Create service groups for ssh and http for each set of pcs.

   - The idea here is to create five service groups. Each service group will
     be for a table. We want to see these PCs grouped together by table
     and include status of their ssh and http services. To do this edit
     and create the file:

   # editor /etc/nagios3/conf.d/servicegroups.cfg

     Here is a sample of the service group for group 1:

define servicegroup {
        servicegroup_name       group1-servers
        alias                   group 1 servers
        members                 pc1,SSH,pc1,HTTP,pc2,SSH,pc2,HTTP,pc3,SSH,pc3,HTTP,pc4,SSH,pc4
        }

        - Note that the members line should wrap and not be on two lines.
        
        - Note that "SSH" and "HTTP" need to be uppercase as this is how the service_description is
          written in the file /etc/nagios3/conf.d/services_nagios2.cfg
          
        - You should create an entry for other groups of servers too

    - Save your changes, verify your work and restart Nagios. Now if you click on
      the Servicegroup menu items in the Nagios web interface you should see
      this information grouped together. 



OPTIONAL
--------

* Check that SNMP is running on the classroom NOC

    - First you will need to add in the appropriate service check for SNMP in the file
      /etc/nagios3/conf.d/services_nagios2.cfg. This is where Nagios is impressive. There
      are hundreds, if not thousands, of service checks available via the various Nagios
      sites on the web. You can see what plugins are installed by Ubuntu in the nagios3
      package that we've installed by looking in the following directory:

    # ls /usr/lib/nagios/plugins

      As you'll see there is already a check_snmp plugin available to us. If you are 
      interested in the options the plugin takes you can execute the plugin from the
      command line by typing:

    # /usr/lib/nagios/plugins/check_snmp
    # /usr/lib/nagios/plugins/check_snmp --help 

      to see what options are available, etc. You can use the check_snmp plugin and
      Nagios to create very complex or specific system checks.

    - Now to see all the various service/host checks that have been created using the
      check_snmp plugin you can look in /etc/nagios-plugins/config/snmp.cfg. You will
      see that there are a lot of preconfigured checks using snmp, including:

      snmp_load
      snmp_cpustats
      snmp_procname
      snmp_disk
      snmp_mem
      snmp_swap
      snmp_procs
      snmp_users
      snmp_mem2
      snmp_swap2
      snmp_mem3
      snmp_swap3
      snmp_disk2
      snmp_tcpopen
      snmp_tcpstats
      snmp_bgpstate
      check_netapp_uptime
      check_netapp_cupuload
      check_netapp_numdisks
      check_compaq_thermalCondition
      
      And, even better, you can create additional service checks quite easily.
      For the case of verifying that snmpd (the SNMP service on Linux) is running we
      need to ask SNMP a question. If we don't get an answer, then Nagios can assume
      that the SNMP service is down on that host. When you use service checks such as
      check_http, check_ssh and check_telnet this is what they are doing as well.

    - In our case, let's create a new service check and call it "check_system". This
      service check will connect with the specified host, use the private community 
      string we have defined in class and ask a question of snmp on that ask - in this
      case we'll ask about the System Description, or the OID "sysDescr.0" -

    - To do this start by editing the file /etc/nagios-plugins/config/snmp.cfg:

    # joe /etc/nagios-plugins/config/snmp.cfg

      At the top (or the bottom, your choice) add the following entry to the file:

# 'check_system' command definition
define command{
       command_name    check_system
       command_line    /usr/lib/nagios/plugins/check_snmp -H '$HOSTADDRESS$' -C
'$ARG1$' -o sysDescr.0
        }
      
      You may wish to copy and paste this vs. trying to type this out.

          Note that "command_line" is a single line. If you copy and paste in joe the line
          may not wrap properly and you may have to manually add the part:
          
                        '$ARG1$' -o sysDescr.0
                        
          to the end of the line.

    - Now you need to edit the file /etc/nagios3/conf.d/services_nagios2.cfg and add
      in this service check. We'll run this check against all our servers in the 
      classroom, or the hostgroup "debian-servers"

    - Edit the file /etc/nagios3/conf.d/services_nagios2.cfg

    # joe /etc/nagios3/conf.d/services_nagios2.cfg

      At the bottom of the file add the following definition:

# check that snmp is up on all servers
define service {
        hostgroup_name                  snmp-servers
        service_description             SNMP
        check_command                   check_system!xxxxxx
        use                             generic-service
        notification_interval           0 ; set > 0 if you want to be renotified
}

      The "xxxxxx" is the community string previously (or to be) defined in class.
     
      Note that we have included our private community string here vs. hard-coding
      it in the snmp.cfg file earlier. You must change the "xxxxx" to be the snmp
      community string given in class or this check will not work.
      
    - Now we must create the "snmp-servers" group in our hostgroups_nagios2.cfg file. 
      Edit the file /etc/nagios3/conf.d/hostgroups_nagios2.cfg and go to the end of the
      file. Add in the following hostgroup definition:
      
# A list of snmp-enabled devices on which we wish to run the snmp service check
define hostgroup {
           hostgroup_name       snmp-servers
                   alias        snmp servers
                   members      noc
          }
          
        - Note that for "members" you could, also, add in the switches and routers for
          group 1 and 2. But, the particular item (MIB) we are checking for "sysDescr.0"
          may not be available on the switches and/or routers, so the check would then fail.

    - Now verify that your changes are correct and restart Nagios.

    - If you click on the Service Detail menu choice in web interface you should see
      the SNMP check appear for the noc host.
      
    - After we do the SNMP presentation and exercises in class, then you could come
      back to this exercise and add in all the classroom PCs to the members list in the
      hostgroups_nagios2.cfg file, snmp-servers hostgroup definition. Remember to list
      your PC as "localhost".