# 1 Introduction

## 1.1 Goals

• Install and configure Nagios

$sudo editor switches.cfg Update the entry: define host { use generic-host host_name sw alias Backbone Switch address 10.10.0.253 } to be define host { use generic-host host_name sw alias Backbone Switch address 10.10.0.253 parents rtrX } Where "rtrX" is the gateway router for your group. I.E., for group 1 you would use "rtr1", for group 2, "rtr2" and so forth. Save and exit from the file. ## 3.2 2. Adding Parents to routers.cfg $ sudo editor routers.cfg

For each entry we will add a "parents" line. So, for the gw definition at the top of the file this should now look like:

define host {
use         generic-host
host_name   gw
alias       Classroom Gateway Router
parents     sw
}

For all the remaining rtrX entries, except for your group, you should a line line that says:

    parents sw

There should be NO PARENTS entry for your group. If you have an entry for "ap1" (classroom wireless access point), then the parents entry is, also, "sw" - same as the other routers.

So, if you are in group 2, then the entries for groups 1, 2 and 3 would look like:

define host {
use         generic-host
host_name   rtr1
alias       Group 1 Router
parents     sw
}

define host {
use         generic-host
host_name   rtr2
alias       Group 2 Router
}

define host {
use         generic-host
host_name   rtr3
alias       Group 3 Router
parents     sw
}

Update the rest of the file correctly and then save and exit from the file.

## 3.3 3. Adding Parents to pcs.cfg

For all the PC entries you should add a "parents" line that has the router for that PC's group, EXCEPT FOR YOUR GROUP - there should be no parents entry for the pcs in your group.

For the noc the parent is the core switch or "sw"

#
# Classroom NOC
#

define host {
use         generic-host
host_name   noc
alias       Workshop NOC machine
parents     sw
}

For PCs in Group 1 entries look like:

#
# Group 1
#

define host {
use         generic-host
host_name   pc1
alias       pc1
parents     rtr1
}

define host {
use         generic-host
host_name   pc2
alias       pc2
parents     rtr1
}


etc

Do this for all the PCs in the remaining groups. I.E., pc5 in Group 2 has a parents statement of:

     parents    rtr2

Just remember NOT to add a parents line for the PCs in your group.

Save and exit from the file.

$sudo service nagios3 restart If you have errors, fix these and try restarting again. Open a web browser to http://pcN.ws.nsrc.org/nagios3 and click on the "Map" link on the left. Your map should now look quite different. You should see a map that represents the Nagios world point of view from your machine. # 4 PART V - Create More Host Groups ## 4.1 0. Prep 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). ## 4.2 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. $ sudo 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 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,pc19,pc20,pc21,pc22,pc23,pc24,pc25,\
pc26,pc27,pc28,pc29,pc30,pc31,pc32,pc33,pc34,pc35,pc36

Be sure that the end of the line has a "" to indicate a new line. Otherwise you will get an error when you go to restart Nagios. Remember that your own PC is "localhost", so skip your pc entry.

Once you have done this, add one more host group for our classroom switch(es). If there is more than just one switch (sw.ws.nsrc.org) include this on the members line below, otherwise the entry at the end of the hostgroups_nagios2.cfg file should look like (COPY and PASTE):

# A list of our switches
define hostgroup {
hostgroup_name  switches
alias           Classroom Switches
members         sw
}

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

# 5 PART VI - Extended Host Information ("making your graphs pretty")

## 5.1 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.

$sudo editor servicegroups.cfg Here is a sample of the service group for group 1: define servicegroup { servicegroup_name group1-services alias group 1 services members pc1,SSH,pc1,HTTP,pc2,SSH,pc2,HTTP,pc3,SSH,pc3,HTTP,pc4,SSH,pc4,HTTP } Note that if the members line is too long you can use the "" at the end to create a new line of members just below. 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. CRITICAL - When you create an entry for your group remember to use "localhost" instead of your "pcN" name since you have only defined your pc as localhost in the file hostgroups_nagios2.cfg. Save your changes, verify your work and restart Nagios. Now if you click on the Service Groups menu item in the Nagios web interface you should see this information grouped together. # 7 PART VIII - Configure Guest Access to the Nagios Web Interface ## 7.1 1. You will edit the file /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. $ sudo 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_all_host_commands=nagiosadmin

Now let's 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_all_host_commands=nagiosadmin

Note we do not give the guest user access to system commands, service commands nor host commands.

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 will need to clear the cookies in your web browser or open an alternate web browser if you have one. 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.

## 7.2 2. Enable External commands in nagios.cfg

This change is required in order to allow users to "Acknowledge" problems with hosts and services in the Web interface. The default file permissions are set up in a secure way to prevent the web interface from updating nagios, so you need to make them slightly more permissive.

First, edit the file "/etc/nagios3/nagios.cfg", and change the line:

    check_external_commands=0

to

    check_external_commands=1

Save the file and exit.

Then, perform the following commands to change directory permissions and to make the changes permanent:

$sudo /etc/init.d/nagios3 stop$ sudo dpkg-statoverride --update --add nagios www-data 2710 /var/lib/nagios3/rw
$sudo dpkg-statoverride --update --add nagios nagios 751 /var/lib/nagios3$ sudo /etc/init.d/nagios3 start

Once this is done, go to "Problems" > "Services (Unhandled)" and find a service in the red (critical) or yellow (warning) state. Click on the service name. Then under "Service commands" click on "Acknowledge this service problem".

The problem should disappear from the list of unhandled problems.