(Quick) Nagios setup

A quick & dirty "guide" to get Nagios monitoring on a local Linux server in no time. This has been done on CentOS, but the same applies to just about any other distro, as long as you take care of the paths to the configuration files.

cp template.HOSTNAME.FQDN.cfg $HOSTNAME.cfg
emacs $HOSTNAME.cfg

Meta X replace-regex HOSTNAME host
Meta X replace-regex $HOSTNAME.FQDN $HOSTNAME

Section "define host":
Replace "Description here" with the real data
Replace "ip.address.here" with the real IP address of the host

Section "define contact":
Replace "Description here" with the real data, a concise description.
email Replace with the real email addresses of the contacts, or the contact that should receive notifications from this server.

Section "define contactgroup":
Replace "Description here" with the real data of the Linux server.
Be sure to add more services to suit your needs, or the needs of the monitored server.
Copy the file to the Nagios directory:

sudo cp $HOSTNAME.cfg /etc/nagios/objects/

Edit the commands file:

sudo emacs /etc/nagios/objects/commands.cfg

Specifically, edit the strings "***** Nagios *****" on 'notify-host-by-email' & 'notify-service-by-email' to something that identifies the box from which the emails are coming from.
I usually leave like this:

** Nagios $HOSTNAME **

Edit Nagio's master configuration file, so it uses the cfg file just created, and discard the default localhost.cfg one.

sudo emacs /etc/nagios/nagios.cfg

Comment the line:

cfg_file=/etc/nagios/objects/localhost.cfg

And add a line with the cfg file just created.

cfg_file=/etc/nagios/objects/$HOSTNAME.cfg

Before launching Nagios, tight a bit the web access:

sudo emacs /etc/httpd/conf.d/nagios.conf

And setup basic security (enable SSL, setup the password protection, limit IP range, etc).

Test it

sudo /usr/bin/nagios -v /etc/nagios/nagios.cfg

And if its OK, launch it.

Here is a copy of "template.HOSTNAME.FQDN.cfg":

## -----------------------------------------------

## History

## -----------------------------------------------

## sudo /usr/bin/nagios -v /etc/nagios/nagios.cfg

define host{
 name                   HOSTNAME-host
 use                    generic-host
 check_period           24x7
 check_interval         5
 retry_interval         1
 max_check_attempts     10
 check_command          check-host-alive
 notification_period    24x7
 notification_interval  120
 notification_options   d,u,r
 contact_groups         HOSTNAME-contactgroup
 register               0
 }

define host{
 use                    HOSTNAME-host
 host_name              HOSTNAME.FQDN
 alias                  Description here
 address                ip.address.here
 }

define contact{
 contact_name           HOSTNAME-contact
 use                    generic-contact
 alias                  Description here
 email                  1@email.com, 2@email.com, 3@email.com
 }

define contactgroup{
 contactgroup_name      HOSTNAME-contactgroup
 alias                  Description here
 members                HOSTNAME-contact
 }

# SERVICE DEFINITIONS

define service{
 name                         HOSTNAME-generic-service
 active_checks_enabled        1
 passive_checks_enabled       1
 parallelize_check            1
 obsess_over_service          1
 check_freshness              0
 notifications_enabled        1
 event_handler_enabled        1
 flap_detection_enabled       1
 failure_prediction_enabled   1
 process_perf_data            1
 retain_status_information    1
 retain_nonstatus_information 1
 is_volatile                  0
 check_period                 24x7
 max_check_attempts           3
 normal_check_interval        5
 retry_check_interval         2
 contact_groups               HOSTNAME-contactgroup
 notification_options         w,u,c,r
 notification_interval        120
 notification_period          24x7
 register                     0
 }

define service{
 name                   HOSTNAME-service
 use                    HOSTNAME-generic-service
 max_check_attempts     4
 normal_check_interval  5
 retry_check_interval   1
 register               0
 }

define service{
 use                  HOSTNAME-service
 host_name            HOSTNAME.FQDN
 service_description  Connectivity
 check_command        check_ping!100.0,20%!500.0,60%
 }

# Define a service to check the disk space of the root partition
# on the local machine.  Warning if < 20% free, critical if
# < 10% free space on partition.

define service{
 use                   HOSTNAME-service
 host_name             HOSTNAME.FQDN
 service_description   Partition /
 check_command         check_local_disk!20%!10%!/
 }

define service{
 use                   HOSTNAME-service
 host_name             HOSTNAME.FQDN
 service_description   Partition /boot
 check_command         check_local_disk!20%!10%!/boot
 }

# Define a service to check the number of currently logged in
# users on the local machine.  Warning if > 20 users, critical
# if > 50 users.

define service{
 use                   HOSTNAME-service
 host_name             HOSTNAME.FQDN
 service_description   Current Users
 check_command         check_local_users!20!50
 }

# Define a service to check the number of currently running procs
# on the local machine.  Warning if > 250 processes, critical if
# > 400 users.

define service{
 use                   HOSTNAME-service
 host_name             HOSTNAME.FQDN
 service_description   Total Processes
 check_command         check_local_procs!250!400!RSZDT
}

define service{
 use                   HOSTNAME-service
 host_name             HOSTNAME.FQDN
 service_description   Current Load
 check_command         check_local_load!5.0,4.0,3.0!10.0,6.0,4.0
}

define service{
 use                   HOSTNAME-service
 host_name             HOSTNAME.FQDN
 service_description   Swap Usage
 check_command         check_local_swap!20!10
}

define service{
 use                   HOSTNAME-service
 host_name             HOSTNAME.FQDN
 service_description   Service SSH
 check_command         check_ssh
}

define service{
 use                   HOSTNAME-service
 host_name             HOSTNAME.FQDN
 service_description   Service HTTP
 check_command         check_http
}

# EoF #