Files: exercises-nagios.txt

Registry Operations Curriculum
Nagios Installation and Configuration

Notes:
------
* Commands preceded with "$" imply that you should execute the command as
  a general user - not as root.
* Commands preceded with "#" imply that you should be working as root.
* Commands with more specific command lines (e.g. "RTR-GW>" or "mysql>") 
  imply that you are executing commands on remote equipment, or within 
  another program.

Exercises
---------

Exercises Part I
----------------

0. Log in to your PC or open a terminal window as the tladmain user.


1. You could nstall Nagios version 3. You would do this as root or as the tldadmin
   user and use the "sudo" command:

    # apt-get install nagios3
    
   Nagios version 3 is already installed, but you can still run the command.


2. Create the Web user password file:

    # htpasswd -c /etc/nagios3/htpasswd.users nagiosadmin

New password:         
Re-type new password: 

   We suggest you use your standard user password used in class.


2. You should already have a working Nagios!

    - Open a browser, and go to

    http://localhost/nagios3/

    - At the login prompt, login as:

        user: nagiosadmin
        pass: 

3. Let's look at the interface together...

    # cd /etc/nagios3/

    # ls -l 
    -rw-r--r-- 1 root root    1882 2008-12-18 13:42 apache2.conf
    -rw-r--r-- 1 root root   10524 2008-12-18 13:44 cgi.cfg
    -rw-r--r-- 1 root root    2429 2008-12-18 13:44 commands.cfg
    drwxr-xr-x 2 root root    4096 2009-02-14 12:33 conf.d
    -rw-r--r-- 1 root root      26 2009-02-14 12:36 htpasswd.users
    -rw-r--r-- 1 root root   42539 2008-12-18 13:44 nagios.cfg
    -rw-r----- 1 root nagios  1293 2008-12-18 13:42 resource.cfg
    drwxr-xr-x 2 root root    4096 2009-02-14 12:32 stylesheets
    
    # ls -l conf.d/

    -rw-r--r-- 1 root root 1695 2008-12-18 13:42 contacts_nagios2.cfg
    -rw-r--r-- 1 root root  418 2008-12-18 13:42 extinfo_nagios2.cfg
    -rw-r--r-- 1 root root 1152 2008-12-18 13:42 generic-host_nagios2.cfg
    -rw-r--r-- 1 root root 1803 2008-12-18 13:42 generic-service_nagios2.cfg
    -rw-r--r-- 1 root root  210 2009-02-14 12:33 host-gateway_nagios3.cfg
    -rw-r--r-- 1 root root  976 2008-12-18 13:42 hostgroups_nagios2.cfg
    -rw-r--r-- 1 root root 2167 2008-12-18 13:42 localhost_nagios2.cfg
    -rw-r--r-- 1 root root 1005 2008-12-18 13:42 services_nagios2.cfg
    -rw-r--r-- 1 root root 1609 2008-12-18 13:42 timeperiods_nagios2.cfg

    Notice that the package does not have renamed filenames for the conf.d 
    directory - they are the same files as used for the Nagios version 2
    Ubuntu package. There was an update made to the host-gateway configuration
    file so this has been renamed.

PART II
Configuring Equipment
-----------------------------------------------------------------------------

0. Order of configuration

Conceptually we will build our configuration files from the "top" of our network down. That
is we define entries for our gateway router and swith first, then our group routers and switches.
Once we have these entries we will add an entry for our NOC machine, then pc1, pc2, pc3, etc...

By going in this order you will have defined the devices that act as parents for other devices.


1. Let's configure Nagios to start monitoring our classroom gateway router:

    # cd /etc/nagios3/conf.d/

    # vi routers.cfg
    
define host {
    use         generic-host
    host_name   bb-gw
    alias       cctld border router
    address     192.168.17.2
}
   
   Now define entries for our two group routers:
    
define host {
    use         generic-host
    host_name   pc1-pc9-gw
    alias       cctld group 1 router
    address     192.168.5.129
}

define host {
    use         generic-host
    host_name   pc10-pc18-gw
    alias       cctld group 2 router
    address     192.168.5.161
}

Save and exit from the file /etc/nagios3/conf.d/routers.cfg


2. Configure our classroom switches

Now that we have our routers configured we can configure our switches. Note that each 
switch will have a parent relationship with the router next to them.

        # vi switches.cfg

First the switch on our classroom backbone:

define host {
    use         generic-host
    host_name   bb-sw
    alias       cctld backbone switch
    address     192.168.17.4
    parents     bb-gw
}

Notice the "parents" entry. You can only add the parent entry once you have a definition for
"bb-gw". We did this in our routers.cfg file, so this will work.

Now add in the switches for the two groups:

define host {
    use         generic-host
    host_name   pc1-pc9-sw
    alias       cctld group 1 switch
    address     192.168.5.130
    parents     pc1-pc9-gw
}

define host {
    use         generic-host
    host_name   pc10-pc18-sw
    alias       cctld group 2 switch
    address     192.168.5.162
    parents     pc10-pc18-gw
}

Save and exit from the file switches.cfg


3. Update the file routers.cfg with parents

The border router does not have a parent for purposes of our class. In reality it does, but 
you have to stop your monitoring somewhere.

Our two group routers, however, now have a parent defined. This is the backbone switch. We 
need to update our group router entries to look like this:

define host {
    use         generic-host
    host_name   pc1-pc9-gw
    alias       cctld group 1 router
    address     192.168.5.129
    parents     bb-sw
}

define host {
    use         generic-host
    host_name   pc10-pc18-gw
    alias       cctld group 2 router
    address     192.168.5.161
    parents     bb-sw
}

Save and exit from the file routers.cfg


4. Create entries for each PC in the classroom

Now that we have our routers and switches defined it is quite easy to create entries for all our
PCs. Think about the parent relationships. The parent of the NOC is the backbone switch. The
parent of pc1 through pc9 is the switch for group 1. The parent for pc10-18 is the switch for
group 2.

Below are three sample entries. One for the NOC, one for pc1 and one for pc10. You should be able
to use this example to create entries for all 18 classroom pcs plus the NOC:

We could put these entries in to separate files, but as our network is small we'll use a single 
file called pcs.cfg.

NOTE! You do not add in an entry for your PC. This has already been defined in the file 
/etc/nagios3/conf.d/localhost_nagios2.cfg. This definition is what define's the Nagios
network viewpoint. So, when you come to the spot where you might add an entry for your PC
you should skip this and go on to the next PC in the list (i.e. from pc1 to pc18).

        # vi pcs.cfg
        
# Our classroom NOC

define host {
    use         generic-host
    host_name   noc
    alias       aroc cctld NOC machine
    address     192.168.17.5
    parents     bb-sw
}

# Group 1 PCs

define host {
    use         generic-host
    host_name   pc1
    alias       pc1 group 1 aroc cctld
    address     192.168.5.131
    parents     pc1-pc9-sw
}

# Group 2 PCs

define host {
    use         generic-host
    host_name   pc10
    alias       pc10 group 2 aroc cctld
    address     192.168.5.170
    parents     pc10-pc18-sw
}

Take the three entries above and now expand this to create the remaining entries for pc1-pc9 and
for pc10-pc18. If you have any questions about IP addresses, etc. you can review the Network 
Diagram for the class linked off the classroom wiki main page at http://localhost/trac/.

Exit and save the file pcs.cfg

Now let's verify that our initial Nagios configuration is working:


5. Verify that your configuration files are OK:

    # nagios3 -v /etc/nagios3/nagios.cfg 

    ... You should get :

Total Warnings: 0
Total Errors:   0

Things look okay - No serious problems were detected during the check.


5. Reload/Restart Nagios

    # /etc/init.d/nagios3 restart

6. Go to the web interface (http://localhost/nagios3) and check that the hosts 
   you just added are now visible in the interface. Click on the "Host Detail" item
   on the left of the Nagios screen to see this.


PART III
Configure Service check for your the classroom NOC
-----------------------------------------------------------------------------

0. Configuring

Now that we have our hardware configured we can start telling Nagios what services to monitor
on the configured hardware, how to group the hardware in interesting ways, how to group
services, etc.

1. Associate a service check for our classroom NOC

    # vi hostgroups_nagios2.cfg

    - Find the hostgroup named "ssh-servers". In the members section of the defintion 
      change the line:

members                 localhost

    to

members                 localhost,noc

Exit and save the file. 

Verify that your changes are OK:

        # nagios3 -v /etc/nagios3/nagios.cfg
        
Restart Nagios to see the new service assocation with your host:

        # /etc/init.d/nagios3 Restart

Click on the "Service Detail" link in the Nagios web interface to see your new entry.


PART IV
Defining Services for all PCs
-----------------------------------------------------------------------------

1. Determine what services to define for what devices

   - This is core to how you use Nagios and network monitoring tools in 
     general. So far we are simply using ping to verify that physical hosts
     are up on our network and we have started monitoring a single service on
     a single host (your PC). The next step is to decide what services you wish
     to monitor for each host in the classroom.

   - In this particular class we have:

     routers:  running ssh and snmp 
     switches: running telnet and possibly ssh as well as snmp
     pcs:      All PCs are running ssh and http
               The NOC is currently running an snmp daemon
              
     So, let's configure Nagios to check for these services for these 
     devices.

2. Check that telnet is running on the workshop switches. 

   If the switches in your workshop are not running telnet you can skip this 
   exercise.

   - You will need to edit the file /etc/nagios3/conf.d/services_nagios2.cfg
     to first define the "check_telnet" and to what group of hosts this 
     command will apply.

   - Edit the file services_nagios2.cfg:

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

   At the bottom of the file add in the new service definition. It will look
   like this:

# check that telnet is running
define service {
        hostgroup_name                  telnet-servers
        service_description             Telnet
        check_command                   check_telnet
        use                             generic-service
        notification_interval           0 ; set > 0 if you want to be renotified
}

   - By default Nagios (on Ubuntu) is pre-configured with web, ssh and ping
     service definition. It turns out, once we are completely done, that you 
     may not need the ping service definition - but, don't remove it yet!

   - Notice the parameter that says:

     hostgroup_name                    telnet-servers

     We need to create this before we try to restart Nagios. Edit the file
     /etc/nagios3/conf.d/hostgroups_nagios2.cfg and at the bottom of the
     file add the following entry:

# A list of your telnet-accessible devices (switches)
define hostgroup {
        hostgroup_name  telnet-servers
                alias           Telnet servers
                members         xxxx,xxxx,xxxx
        }

   - xxxx = name of each switch (bb-sw, pc1-pc9-sw, pc10-pc18-sw)

     Note the "members" section. Hopefully when you defined your switches
     in the switches.cfg file this is what you used for the host_name directive
     for the switches.

   - Save your changes and check your configuration:

   # nagios3 -v /etc/nagios3/nagios.cfg

   - Restart Nagios and see if you notice the changes you've made. Note that 
     the actual check of the telnet service will most likely be in a "pending"
     state at first.

3.) Verify that SSH is running on the routers and workshop PCs images

   - In the file services_nagios2.cfg there is already an entry for the SSH 
     service check, so you do not need to create this step. Instead, you 
     simply need to re-define the "ssh-servers" entry in the file
     /etc/nagios3/conf./hostgroups_nagios2.cfg. The initial entry in the file
     looked like:

# A list of your ssh-accessible servers
define hostgroup {
        hostgroup_name  ssh-servers
                alias           SSH servers
                members         localhost
        }

     What do you think you should change? Correct, the "members" line. You should
     add in entries for all the classroom pcs, routers and  the switches that run ssh. 
     With this information and the network diagram you should be able complete this entry.
     
         Note: leave in "localhost" - This is your PC and represents Nagios' network point of
         view. So, for instance, if you are on "pc3" you would not include "pc3" in the list
         of all the classroom pcs as it is represented by the "localhost" entry.
         
         The "members" entry will be a long line and will likely wrap on the screen.

    - Once you are done, run the pre-flight check:

    # nagios3 -v /etc/nagios3/nagios.cfg

    If everything looks good, then restart Nagios and see your changes in the 
    Nagios web interface.

4.) Check that http is running on all the classroom PCs. 

    - Like ssh, there is already a check_http service defined and it automatically
      applies to the http-servers group. (Note, you can add additional groups of hosts
      for any service check if you wish). So, you need to update the "http-servers" entry
      in the file /etc/nagios3/conf.d/hostgroups_nagios2.cfg to include all the workshop
      PCs running http (i.e. Apache Web Server).

    - See the previous exercise and make the appropriate change to do this. If you have
      any questions ask your instructor for help.
     

5.) 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

      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:

    # vi /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 past this vs. trying to type this out.

          Note that "command_line" is a single line. If you copy and paste in vi 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

    # vi /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.
      
    - 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".
      

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

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.

    # vi /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 to confirm the exact number of machines and names
      in your workshop.

                members         localhost,pc1,pc2,pc3,pc4,pc5,pc6,pc7,pc8,pc9
                                pc10,pc11,pc12,pc13,pc14,pc15,pc16,pc17,pc18

        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.

      - Once you have done this, add in two more entries. 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.
    

PART V
Extended Host Information ("making your graphs pretty")
-----------------------------------------------------------------------------

1. Update extinfo_nagios2.cfg 

    - If you would like to use appropriate icons for your defined hosts in
      Nagios this is where you do this. We have the three types of devices:

      Cisco routers
      Cisco switches
      Ubuntu servers

      There is a fairly large repository of icon images available for you to
      use located here:

      /usr/share/nagios/htdocs/images/logos/

      these were installed by default as dependent packages of the nagios3
      package in Ubuntu. In some cases you can find model-specific icons for
      your hardware, but to make things simpler we will use the following 
      icons for our hardware:

      /usr/share/nagios/htodcs/images/logos/base/debian.*
      /usr/share/nagios/htdocs/images/logos/cook/router.*
      /usr/share/nagios/htdocs/images/logos/cook/switch.*

    - The next step is to edit the file /etc/nagios3/conf.d/extinfo_nagios2.cfg
      and tell nagios what image you would like to use to represent your devices.

    # vi /etc/nagios3/conf.d/extinfo_nagios2.cfg

      Here is what an entry for your routers looks like (there is already an entry
      for debian-servers that will work as is). Note that the router model (3600) 
      is not all that important. The image used represents a router in general.

define hostextinfo {
        hostgroup_name   routers 
        icon_image       cook/router.png
        icon_image_alt   Cisco Routers (3600) 
        vrml_image       router.png 
        statusmap_image  cook/router.gd2
}

      Now add an entry for your switches. Once you are done check your
      work and restart Nagios. Take a look at the Status Map in the web interface.
      It should be much nicer.      

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

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

   - The idea here is to create three service groups. Each service group will
     be for the group of PCs that are connected to each router xxxxxxx,
     yyyyyy, zzzzzz, etc. We want to see these PCs grouped together
     and include status of their ssh and http services. To do this edit
     and create the file:

   # vi /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,HTTP,pc5,SSH,
                        pc5,HTTP,pc6,SSH,pc6,HTTP,pc7,SSH,pc7,HTTP,pc8,SSH,pc8,HTTP,pc9,SSH,pc9,HTTP
        }

        - 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 the group 2 servers as well.

    - 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. 

    - Be sure you to this for TLD1 through TLD8 to create a servicegroup of SSH
      and HTTP servers for all 8 TLDs in the classroom.


PART VII
Configure Guest Access to the Nagios Web Interface
-----------------------------------------------------------------------------

1. Edit /etc/nagios3/cgi.cfg to give read only guest user access to the Nagios 
   web interface.

    - By default Nagios is configured to give full r/w access via the Nagios
      web interface to the user nagiosadmin. You can change the name of this
      user, add other users, change how you authenticate users, what users
      have access to what resources and more via the cgi.cfg file.

    - First, lets create a "guest" user and password in the htpasswd.users
      file.
      
    # cd /etc/nagios3
    # htpasswd /etc/nagios3/htpasswd.users guest

      You can use any password you want (or none). A password of "guest" is 
      not a bad choice.

    - Next, edit the file /etc/nagios3/cgi.cfg and look for what type of access
      has been given to the nagiosadmin user. By default you will see the following 
      directives (note, there are comments between each directive):

      authorized_for_system_information=nagiosadmin
      authorized_for_configuration_information=nagiosadmin
      authorized_for_system_commands=nagiosadmin
      authorized_for_all_services=nagiosadmin
      authorized_for_all_hosts=nagiosadmin
      authorized_for_all_service_commands=nagiosadmin
      authorized_for_all_host_commands=nagiosadmin

      Now lets tell Nagios to allow the "guest" user some access to 
      information via the web interface. You can choose whatever you would
      like, but what is pretty typical is this:

      authorized_for_system_information=nagiosadmin,guest
      authorized_for_configuration_information=nagiosadmin,guest
      authorized_for_system_commands=nagiosadmin
      authorized_for_all_services=nagiosadmin,guest
      authorized_for_all_hosts=nagiosadmin,guest
      authorized_for_all_service_commands=nagiosadmin
      authorized_for_all_host_commands=nagiosadmin

    - Once you make the changes, save the file cgi.cfg, verify your 
      work and restart Nagios. 

    - To see if you can log in as the "guest" user you may need to clear 
      the cookies in your web browser. You will not notice any difference
      in the web interface. The difference is that a number of items that
      are available via the web interface (forcing a service/host check, 
      scheduling checks, comments, etc.) will not work for the guest 
      user.

Last update 20 July 2010 by HA