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These are supplement notes I had taken down a while back doing an install of nagios and n2rrd on a Fedora-7 box and recently came very handy when doing the install in a redhat (RHEL-3) box as well:

Nagios Install:

On RHEL3, I used (dags rpms) rpmforge. Here is my yum.conf for rpmforge:

Notes: I settled for icmp instead of ping, as it is a lot faster. However, icmp required setting setuid for "/usr/lib/nagios/plugins/check_icmp" for it to work. Also, had to rebuild nagios-plugins from source as root in order for the plugin to be installed.

1. Edit "etc/httpd/conf.d/nagios" and add the IPs and users to allow access.

   Here is what it looks like:

   ScriptAlias /nagios/cgi-bin "/usr/lib/nagios/cgi";
   <Directory "/usr/lib/nagios/cgi";>
      SSLRequireSSL
      Options ExecCGI
      AllowOverride None
      Order deny,allow
      Deny from all
      Allow from xxx.xxx.xxx.xxx
      AuthUserFile /var/www/.htpasswd
      AuthGroupFile /var/www/.htgroup
      AuthName "Protected"
      AuthType Basic
      <Limit GET>
        require group administrator
      </Limit>
      satisfy all
   </Directory>
   
   Alias /nagios "/usr/share/nagios"<br /><Directory "/usr/share/nagios"&gt;
      SSLRequireSSL
      Options None
      AllowOverride None
      Order deny,allow
      Deny from all
      Allow from xxx.xxx.xxx.xxx
      AuthUserFile /var/www/.htpasswd
      AuthGroupFile /var/www/.htgroup
      AuthName "Protected"
      AuthType Basic
      <Limit GET>
        require group  administrator
      </Limit>
      satisfy all
   </Directory>
   

2. Reload httpd.
3. Edit "/etc/nagios/nagios.cfg":

   Below are the main setting to look for:
   

   # cfg_file=/etc/nagios/localhost.cfg
cfg_file=/etc/nagios/contactgroups.cfg
cfg_file=/etc/nagios/contacts.cfg
#cfg_file=/etc/nagios/dependencies.cfg
#cfg_file=/etc/nagios/escalations.cfg
cfg_file=/etc/nagios/hostgroups.cfg
cfg_file=/etc/nagios/hosts.cfg
cfg_file=/etc/nagios/services.cfg
cfg_file=/etc/nagios/timeperiods.cfg
cfg_file=/etc/nagios/serviceextinfo.cfg
process_performance_data=1r />host_perfdata_command=process-host-perfdata-n2rrd
service_perfdata_command=process-service-perfdata-n2rrd />enable_flap_detection=1

   Here is what the config file looks like:
   

   # egrep -v "#|^$" /etc/nagios/nagios.cfg
log_file=/var/log/nagios/nagios.log
cfg_file=/etc/nagios/commands.cfg
cfg_file=/etc/nagios/contactgroups.cfg
cfg_file=/etc/nagios/contacts.cfg
cfg_file=/etc/nagios/hostgroups.cfg
cfg_file=/etc/nagios/hosts.cfg
cfg_file=/etc/nagios/services.cfg
cfg_file=/etc/nagios/timeperiods.cfg
cfg_file=/etc/nagios/serviceextinfo.cfg
object_cache_file=/var/log/nagios/objects.cache
resource_file=/etc/nagios/resource.cfg
status_file=/var/log/nagios/status.dat
nagios_user=nagios
nagios_group=nagios
check_external_commands=0 />command_check_interval=-1 />command_file=/var/log/nagios/rw/nagios.cmd
external_command_buffer_slots=4096
comment_file=/var/log/nagios/comments.dat
downtime_file=/var/log/nagios/downtime.dat
lock_file=/var/run/nagios.pid
temp_file=/var/log/nagios/nagios.tmp
event_broker_options=-1
log_rotation_method=d
log_archive_path=/var/log/nagios/archives
use_syslog=1
log_notifications=1
log_service_retries=1
log_host_retries=1
log_event_handlers=1
log_initial_states=0
log_external_commands=1
log_passive_checks=1
service_inter_check_delay_method=s
max_service_check_spread=30<br />service_interleave_factor=s<br />host_inter_check_delay_method=s
max_host_check_spread=30
max_concurrent_checks=0
service_reaper_frequency=10<br />check_result_buffer_slots=4096
auto_reschedule_checks=0
auto_rescheduling_interval=30
auto_rescheduling_window=180
sleep_time=0.25
service_check_timeout=60
host_check_timeout=30
event_handler_timeout=30
notification_timeout=30
ocsp_timeout=5
perfdata_timeout=5
retain_state_information=1r />state_retention_file=/var/log/nagios/retention.dat
retention_update_interval=60
use_retained_program_state=1
use_retained_scheduling_info=0
interval_length=60
use_aggressive_host_checking=0
execute_service_checks=1
accept_passive_service_checks=1
execute_host_checks=1
accept_passive_host_checks=1
enable_notifications=1
enable_event_handlers=1
process_performance_data=1r />host_perfdata_command=process-host-perfdata
service_perfdata_command=process-service-perfdata
obsess_over_services=0
check_for_orphaned_services=1
check_service_freshness=1 />service_freshness_check_interval=60
check_host_freshness=0
host_freshness_check_interval=60
aggregate_status_updates=1r />status_update_interval=15 />enable_flap_detection=1
low_service_flap_threshold=5.0
high_service_flap_threshold=20.0
low_host_flap_threshold=5.0<br />high_host_flap_threshold=20.0
date_format=us
p1_file=/usr/bin/p1.pl
illegal_object_name_chars=`~!$%^&*|'"<>;?,()=
illegal_macro_output_chars=`~$&|'"<>r />use_regexp_matching=0
use_true_regexp_matching=0r />admin_email=nagios
admin_pager=pagenagios
daemon_dumps_core=0

4. Since I've separated out the config files, I copied the samples from "/etc/nagios/localhost.cfg" and setup the configurations from the example file. Make sure to use "cp -a" so the user/group permissions is maintained.

   Basically, hosts.cfg describes the hosts you want to monitor, services.cfg describes the services you want to monitor on each host, commands.cfg is the check commands used by services.cfg to check the services. If you want to check a service you probably have to add a command to do so. contacts.cfg is the people who will be contacted in case of a problem, contactgroups.cfg is the groups of people, hostgroups.cfg is the groups of hosts. nagios.cfg is the master config file.

   To add a new machine you will need to edit hosts.cfg (add the machine), hostgroups.cfg (put it in a hostgroup), services.cfg (add the services to be checked on the machine).

   To add a new administrator, you will need to edit contacts.cfg (add the new person) and contactgroups.cfg (put them in a contact group or create one).

5. Create the corresponding users with htpasswd command, also setup group.
   
   # htpasswd -c /var/www/.htpasswd <nagiosadmin>
6. Add user to the admin group.
   
   # cat <<EOF > /var/www/.htgroup
> administrator: <nagiosadmin>
> EOF
7. Edit "/etc/nagios/cgi.cfg" to include the user to have additional authorization.
   
   # egrep -v "#|^$" /etc/nagios/cgi.cfg
main_config_file=/etc/nagios/nagios.cfg
physical_html_path=/usr/share/nagios
url_html_path=/nagios
show_context_help=0
use_authentication=1
authorized_for_system_information=<nagiosadmin>
authorized_for_configuration_information=<nagiosadmin&gt;
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>
default_statusmap_layout=5r />default_statuswrl_layout=4r />ping_syntax=/bin/ping -n -U -c 5 $HOSTADDRESS$
refresh_rate=90

n2rrd install:

1. See install notes at: n2rrd.diglinks.com

   Run below commands to install, create required directories and setup the right directory permissions:
   

   # yum install rrdtool rrdtool-perl
# wget http://n2rrd.diglinks.com/download/n2rrd-1.3.1.tar.gz
# tar -xvzf n2rrd-1.3.1.tar.gz
# cd n2rrd-1.3.1
# sh ./install.sh
# for fdist in `find /etc/n2rrd -name dist-*`; do fnew=`echo $fdist | sed 's/dist-//'`; mv $fdist $fnew; done
# mkdir /var/www/html/n2rrd
# chown apache /var/www/html/n2rrd
# mkdir /var/log/nagios/rra
# chown nagios:nagios /var/log/nagios/rra
# cp rrd2graph.cgi /var/www/cgi-bin/

2. Edit "/etc/n2rd/n2rrd.conf"
   
   # egrep -v "#|^$" /etc/n2rrd/n2rrd.conf
CONF_DIR = /etc/n2rrd
RRA_DIR = /var/log/nagios/rra
TEMPLATES_DIR = templates
SERVICE_NAME_MAPS = templates/maps/service_name_maps
LOGFILE   &nbsp; = /var/log/nagios/rra/n2rrd.log<br />DOCUMENT_ROOT = /var/www/html
CACHE_DIR = n2rrd
TMPDIR=/tmp
RRDTOOL = /usr/bin/rrdtool
RRD_PATH_HIDDEN=1
NAGIOS_HOST_URL=0
CGIBIN = cgi-bin
NAGIOS_CGIBIN = nagios/cgi-bin
THUMB_DISPLAY = Daily
THUMB_DISPLAY_COLUMNS = 3
THUMB_HEIGHT = 100
THUMB_WIDTH = 200
ZOOM_JS = js/zoom.js
SAVE_NAGIOS_ENVIRONMENT_VARS = 1
3. Add the process-host and process-service performance commands for n2rrd in "/etc/nagios/commang.cfg":
   

   #### n2rrd ####
   # Host Performance processing command
   define command{
     command_name process-host-perfdata-n2rrd />  command_line /usr/local/bin/n2rrd.pl -d -c /etc/n2rrd/n2rrd.conf -e $SERVICEEXECUTIONTIME$ \
     -l $SERVICELATENCY$ -T $LASTHOSTCHECK$ -H $HOSTNAME$ -s "check_ping" -o "$HOSTOUTPUT$"
   }
   # Service Performance processing command
   define command{
     command_name process-service-perfdata-n2rrd
     command_line /usr/local/bin/n2rrd.pl -d -c /etc/n2rrd/n2rrd.conf -e $SERVICEEXECUTIONTIME$ \
     -l $SERVICELATENCY$ -T $LASTSERVICECHECK$ -H $HOSTNAME$ -s "$SERVICEDESC$" -o "$SERVICEPERFDATA$"<br />}
   

4. Create templates if not already existing for the particular service.
5. Edit "/etc/n2rrd/templates/maps/service_name_maps" and add the necessary maps.
   
   HTTP: http
ICMP: icmp
6. Check the setup with:
   
   # nagios -v /etc/nagios/nagios.cfg
7. Once the configs are sorted out and without errors, start nagios via:
   
   # /etc/init.d/nagios start

Notes:

• If building rpm package for nagios-plugins, build as root so it will build the root plugins - eg. check_icmp which is much faster that using check_ping
  
  # chmod u+s /var/lib/nagios/plugins/check_icmp
• Install vrml plugin to view 3D model.

  To install freewrl In ubuntu:
  

  $ sudo apt-get install lesstif2