Nagios Server

##How to install Nagios server on Centos Machine

    ##What is Nagios Server?

Nagios® Server Monitoring software is open source software that provides host, service and network monitoring capabilities. Nagios Server Monitoring software monitors disk space usage, CPU usage, memory usage, VPN tunnels, router and switches, databases, and network services. Nagios server monitoring software and other performance management products are used to manage server performance.

• Installation Process

    ##What will u end up?

  • If you follow these instructions, here’s what you will end up with:
    • Nagios and the plugin will be installed in path: /usr/local/nagios
    • Nagios will be configured to monitor a few aspects of your local system (CPU load, disk usage, etc.)
    • The Nagios web interface will be accessible at http://localhost/nagios/

    ##  Prerequisites

    • During portions of the installation you’ll need to have root access to your machine.
    • You also need to give it a static IP address.
    • Make sure you’ve installed the following packages on your Fedora installation before continuing.
      • Apache
      • PHP
      • GCC compiler
      • GD development libraries

      1.      We can use yum to install these packages by running as Root

      [root@monitoring ~]# yum -y install httpd php gcc gclib glibc-common gd gd-devel

      2.      Create Account for Nagios Server

      [root@monitoring ~]# useradd -m nagios

      [root@monitoring ~]# passwd nagios

      [root@monitoring ~]# usermod -a -G nagcmd nagios

      [root@monitoring ~]# usermod -a -G nagcmd apache

      3.      Create a directory for storing the Nagios and plugin from downloads

      [root@monitoring ~]# mkdir downloads/

      [root@monitoring ~]# cd downloads/

      Download the source code tarballs of both Nagios and the Nagios plugins (visit http://www.nagios.org/download for links to the latest versions). Now I am using these version : nagios-3.2.0 and nagios plugins 1.4.15

      4.      We need to extract them

      [root@monitoring downloads]# tar xvf nagios-3.2.0.tar.gz

      [root@monitoring downloads]# cd nagios-3.2.0

      5.      Start compiling it

      [root@monitoring nagios-3.2.0]# ./configure –with-command-group=nagcmd

      [root@monitoring nagios-3.2.0]# make install

      [root@monitoring nagios-3.2.0]# make install-init

      [root@monitoring nagios-3.2.0]# make install-config

      [root@monitoring nagios-3.2.0]# make install-commandmode

      [root@monitoring nagios-3.2.0]# make install-webconf

      6.      Create a nagiosadmin account for logging into the Nagios web interface. Remember the password you assign to this account.

      [root@monitoring conf.d]# htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

      7.      Restard apache service to make the new setting take effect

      [root@monitoring conf.d]# service httpd restart

      Stopping httpd:                                            [  OK  ]

      Starting httpd:                                            [  OK  ]

      8.      Extract and compile nagios plugin

      [root@monitoring downloads]# tar xvf nagios-plugins-1.4.15.tar.gz

      [root@monitoring downloads]# cd nagios-plugins-1.4.15

      [root@monitoring downloads]# cd nagios-plugins-1.4.15

      [root@monitoring nagios-plugins-1.4.15]# ./configure –with-nagios-user=nagios –with-nagios-group=nagios

      [root@monitoring nagios-plugins-1.4.15]# make

      [root@monitoring nagios-plugins-1.4.15]# make install

      9.      Add Nagios to the list of system service and have it automatically start when the system boots.

      [root@monitoring ~]# chkconfig –add nagios

      [root@monitoring ~]# chkconfig nagios on

      10.  Test service whether it is working or not

      [root@monitoring ~]# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

      Checking global event handlers…

      Checking obsessive compulsive processor commands…

      Checking misc settings…

      Total Warnings: 0

      Total Errors: 0

      11.  Fedora ships with SELinux (Security Enhanced Linux) installed and in Enforcing mode by default. This can result in “Internal Server Error” messages when you attempt to access the Nagios CGIs.

      [root@monitoring ~]# vi /etc/selinux/config

      #       permissive – SELinux prints warnings instead of enforcing.

      #       disabled – SELinux is fully disabled.

      #SELINUX=enforcing

      SELINUX=disabled

      # SELINUXTYPE= type of policy in use. Possible values are:

      #       targeted – Only targeted network daemons are protected.

      #       strict – Full SELinux protection.

      SELINUXTYPE=targeted

      Noted: After changes it you must reboot to make it effect.

      12.  Instead of disabling SELinux or setting it to permissive mode, you can use the following command to run the CGIs under SELinux enforcing/targeted mode:

      [root@monitoring ~]#  chcon -R -t httpd_sys_content_t /usr/local/nagios/sbin/

      [root@monitoring ~]#  chcon -R -t httpd_sys_content_t /usr/local/nagios/share/

      13.      Start access to nagios server: http://server-ip/nagios

      14.      How to monitor Linux/Unix machine (NRPE addon)

      • Intrudution:

      We will show you about how you can monitor “private” services and attributes of Linux server, such as:

      – CPU Load

      – Memory usage

      –  Disk usage

      – Logged in users

      – Running processes ………

      • Moreover, we can monitor services that are provided by Linux Servers (HTTP,FTP, SSH, SMTP, etc…..)
      • There are several different ways to monitor attributes or remote Linux/Unix servers. One is by

      using shared SSH keys and the check_by_ssh plugin to execute plugins on remote servers. This

      method will not be covered here, but can result in high load on your monitoring server if you

      are monitoring hundreds or thousands of services. The overhead of setting up/destroying SSH connections is the cause of this.

      • Another common method of monitoring remote Linux/Unix hosts is to use the NRPE addon.

      NRPE allows you to execute plugins on remote Linux/Unix hosts. This is useful if you need to

      monitor local resources/attributes like disk usage, CPU load, memory usage, etc. on a remote

      host.

      

      15. Installation NRPE on Remote Server:

      • We need create Nagios user account on remote server to monitored

      [root@ssh ~]# useradd nagios

      [root@ssh ~]# passwd nagios

      [root@ssh ~]#

      • Download and install Nagios plugins on this link: www.nagios.org/download/download.php

      [root@ssh ~]# mkdir -p /opt/Nagios

      [root@ssh ~]# cd /opt/Nagios/

      • We have to extract Files:

      [root@ssh Nagios]# tar xvf nagios-plugins-1.4.15.tar.gz

      [root@ssh Nagios]# ll

      total 2368

      drwxrwxrwx 16 test   root      4096 Mar 25 07:34 nagios-plugins-1.4.15

      -rw-r–r–  1 root   root   2095419 Sep  7  2010 nagios-plugins-1.4.15.tar.gz

      drwxrwxr-x  6 nagios nagios    4096 Mar 25 07:38 nrpe-2.8

      -rw-r–r–  1 root   root    293332 Mar 31  2012 nrpe-2.8.tar.gz

      [root@ssh Nagios]# cd nagios-plugins-1.4.15

      [root@ssh nagios-plugins-1.4.15]#

      • Compile and Congigure Nagios Plugins : We need the openssl-devel, GCC compiler and GD development libraries package installed to compile plugin with ssl support:

      [root@ssh nagios-plugins-1.4.15]# yum install openssl-devel gcc glibc glibc-common gd gd-devel

      [root@ssh nagios-plugins-1.4.15]#

      • Start to install plugin:

      [root@ssh nagios-plugins-1.4.15]# ./configure –with-nagios-user=nagios –with-nagios-group=nagios

      [root@ssh nagios-plugins-1.4.15]# make

      [root@ssh nagios-plugins-1.4.15]# make install

      [root@ssh nagios-plugins-1.4.15]#

      • The permission on the plugin directory and the plugins will need to be changed to nagios user:

      [root@ssh nagios-plugins-1.4.15]# chown nagios:nagios /usr/local/nagios/

      [root@ssh nagios-plugins-1.4.15]# chown -R nagios:nagios /usr/local/nagios/libexec/

      [root@ssh nagios-plugins-1.4.15]

      • Anyway, we need install xinted as well:

      [root@ssh nagios-plugins-1.4.15]# yum install xinetd

      [root@ssh nagios-plugins-1.4.15]#

      • Download nad install NRPE Daemon
        • As we already downloaded in this location and start extract:

      [root@ssh Nagios]# tar xvf nrpe-2.8.tar.gz

      [root@ssh Nagios]# ll

      total 2368

      drwxrwxrwx 16 test   root      4096 Mar 25 07:34 nagios-plugins-1.4.15

      -rw-r–r–  1 root   root   2095419 Sep  7  2010 nagios-plugins-1.4.15.tar.gz

      drwxrwxr-x  6 nagios nagios    4096 Mar 25 07:38 nrpe-2.8

      -rw-r–r–  1 root   root    293332 Mar 31  2012 nrpe-2.8.tar.gz

      [root@ssh Nagios]#

      • Compile and configure NRPE file

      [root@ssh Nagios]# cd nrpe-2.8

      [root@ssh nrpe-2.8]# ./configure

      [root@ssh nrpe-2.8]# make

      [root@ssh nrpe-2.8]# make all

      [root@ssh nrpe-2.8]# make install-plugin

      [root@ssh nrpe-2.8]# make install-daemon

      [root@ssh nrpe-2.8]# make install-daemon-config

      [root@ssh nrpe-2.8]# make install-xinetd

      [root@ssh nrpe-2.8]#

      • Configure NRPE Configuration file:

        • We have to add Nagios Monitoring server ip address as below on remote server:

      [root@ssh nrpe-2.8]# vim /etc/xinetd.d/nrpe

      # default: on

      # description: NRPE (Nagios Remote Plugin Executor)

      service nrpe

      {

      flags           = REUSE

      socket_type     = stream

      port            = 5666

      wait            = no

      user            = nagios

      group           = nagios

      server          = /usr/local/nagios/bin/nrpe

      server_args     = -c /usr/local/nagios/etc/nrpe.cfg –inetd

      log_on_failure  += USERID

      disable         = no

      only_from       = 127.0.0.1 192.168.1.173

      }

      • Moreover, we need edit service file entry, add entry for nrpe daemon:

      [root@ssh nrpe-2.8]# vim /etc/services

      chargen         19/tcp          ttytst source

      chargen         19/udp          ttytst source

      ftp-data        20/tcp

      ftp-data        20/udp

      #Service NRPE ###

      nrpe 5666/tcp

      # 21 is registered to ftp, but also used by fsp

      ftp             21/tcp

      • Make xinetd starts at boot and restart it:

      [root@ssh nrpe-2.8]# chkconfig xinetd on

      [root@ssh nrpe-2.8]# service xinetd restart

      Stopping xinetd:                                           [  OK  ]

      Starting xinetd:                                           [  OK  ]

      [root@ssh nrpe-2.8]#

      • Test NRPE Daemon Installation: We can check daemon is running and listening on port 5666: Output should be as below:

      [root@ssh nrpe-2.8]# netstat -at |grep nrpe

      getnameinfo failed

      getnameinfo failed

      tcp        0      0 *:nrpe                      *:*                         LISTEN

      [root@ssh nrpe-2.8]#

      • Check NRPE daemon is functioning: Output should be NRPE version

      [root@ssh nrpe-2.8]# /usr/local/nagios/libexec/check_nrpe -H localhost

      NRPE v2.8

      [root@ssh nrpe-2.8]#

      • Open Port 5666 on Firewall
        • Make sure to open 5666 on the firewall of the remote server so that the Nagios monitoring server can access the NRPE daemon:

        16.Set up Nagios Monitoring Host Server

        • Download and install NRPE Plugin

          • We can download link from here: http://www.nagios.org/download
          • We can save file to directory on: /download

        [root@monitoring downloads]# ll

        total 5688

        drwxrwxr-x 14 nagios nagios    4096 Aug 28 20:52 nagios-3.2.0

        -rw-r–r–  1 root   root   3170967 Sep  7  2010 nagios-3.2.0.tar.gz

        drwxrwxrwx 16 test   root      4096 Aug 28 21:01 nagios-plugins-1.4.15

        -rw-r–r–  1 root   root   2095419 Sep  7  2010 nagios-plugins-1.4.15.tar.gz

        -rw-r–r–  1 root   root    293332 Mar 31 16:53 nrpe-2.8.tar.gz

        [root@monitoring downloads]#

        • After we extract file:

        [root@monitoring downloads]# tar xvf nrpe-2.8.tar.gz

        [root@monitoring downloads]# cd nrpe-2.8

        [root@monitoring nrpe-2.8]#

        • Compile and configure NRPE: We need install package: openssl-devel to compile with ssl support:

        [root@monitoring nrpe-2.8]# yum install openssl-devel

        [root@monitoring nrpe-2.8]# ./configure

        [root@monitoring nrpe-2.8]# make all

        [root@monitoring nrpe-2.8]# make install-plugin

        [root@monitoring nrpe-2.8]#

        • Test connection to NRPE daemon on Remote Server: To make sure that the NRPE on our Nagios server can communicate with the NRPE daemon on the remote server we want to monitor. Please follow as below:

        [root@monitoring nrpe-2.8]# /usr/local/nagios/libexec/check_nrpe -H 192.168.1.172

        NRPE v2.8

        [root@monitoring nrpe-2.8]#

        • Moreover, we cannot communicate with remote server, check your firewall:

        [root@monitoring nrpe-2.8]# /usr/local/nagios/libexec/check_nrpe -H 192.168.1.172

        Connection refused or timed out

        [root@monitoring nrpe-2.8]#

        • Create NRPE Command Definition:
          • The command definition, we need to be created in order for the check_nrpe plugin to be used by nagios Server: You can follow as below:

        [root@monitoring nrpe-2.8]# vim /usr/local/nagios/etc/objects/commands.cfg

        ##NRPE CHECK COMMAND #

        # Command to use NRPE to check remote host systems

        ##################################################################################

        define command{

        command_name check_nrpe

        command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$

        }

        • Start to create new Linux object template:

          • To be able to add the remote linux machine to Nagios we need to create object file template and add some object definitions:
          • Create new linux-ssh object template file:

        [root@monitoring ~]# vim /usr/local/nagios/etc/objects/linux-ssh.cfg

        define host{

        name linux-ssh ; Name of this template

        use linux-ssh ; Inherit default values

        check_period 24×7

        check_interval 5

        retry_interval 1

        max_check_attempts 8

        check_command check-host-alive

        notification_period 24×7

        notification_interval 30

        contact_groups admins

        register 0 ; DONT REGISTER THIS – ITS A TEMPLATE

        }

        define host{

        #use linux-box-remote ; Inherit default values from a template

        use linux-ssh ; Inherit default values from a template

        host_name Centos ; The name we’re giving to this server

        alias Centos ; A longer name for the server

        address 192.168.1.172 ; IP address of the server

        }

        define service{

        use generic-service

        host_name Centos

        service_description CPU Load

        check_command check_nrpe!check_load

        }

        define service{

        use generic-service

        host_name Centos

        service_description Current Users

        check_command check_nrpe!check_users

        }

        define service{

        use generic-service

        host_name Centos

        service_description Disk /

        check_command check_nrpe!check_disk_root

        }

        define service{

        use generic-service

        host_name Centos

        service_description Disk /home

        check_command check_nrpe!check_home

        }

        define service{

        use generic-service

        host_name Centos

        service_description /

        check_command check_nrpe!check_root

        define service {

         

        use generic-service

        host_name Centos

        service_description Check_Procs

        check_command check_nrpe!check_zombie_procs

         

        }

        define service {

        use generic-service

        host_name Centos

        service_description Check_Total_Procs

        check_command check_nrpe!check_total_procs

        }

        define service{

        use                             generic-service         ; Name of service template to use

        host_name                       Centos

        service_description             PING

        check_command                   check_ping!100.0,20%!500.0,60%

        }

        define service{

        use                             generic-service         ; Name of service template to use

        host_name                       Centos

        service_description             SSH

        check_command                   check_ssh

        notifications_enabled           0

        }

        define service{

        use                             generic-service         ; Name of service template to use

        host_name                       Centos

        service_description             HTTP

        check_command                   check_http

        notifications_enabled           0

        }

        define service{

        use                             generic-service         ; Name of service template to use

        host_name                       Centos

        service_description             Swap Partition

        check_command                   check_nrpe!check_swap

        notifications_enabled           0

        }

        • Make sure you active the linux-ssh.cfg template:

        [root@monitoring ~]# vim /usr/local/nagios/etc/nagios.cfg

        # Definitions for monitoring the local (Linux) host

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

        cfg_file=/usr/local/nagios/etc/objects/linux-ssh.cfg

        • To check whether the Nagios configuration is working or not:

        [root@monitoring ~]# /usr/local/nagios/bin/nagios -v

        /usr/local/nagios/etc/nagios.cfg

        Checking obsessive compulsive processor commands…

        Checking misc settings…

        Total Warnings: 0

        Total Errors: 0

        Things look okay – No serious problems were detected during the pre-flight

        Check

        • Restart Nagios Service:

        [root@monitoring ~]# service nagios restart

        Running configuration check…done.

        Stopping nagios: done.

        Starting nagios: done.

        [root@monitoring ~]#

        

        • Sometime you will get some error on Nagios like on Disk space as below:

        

        • Below is step to solve this problem: Go to check on remote server and check your system hard disk architecture.

        [root@ssh ~]# df -h

        Filesystem            Size  Used Avail Use% Mounted on

        /dev/mapper/VolGroup00-LogVol00

        39G  1.6G   35G   5% /

        /dev/hda1              99M   19M   76M  20% /boot

        tmpfs                 125M     0  125M   0% /dev/shm

        [root@ssh ~]#

        • After that, we can go to check and change hard disk name: from “hba1” to “hda1” as below:

        [root@ssh ~]# vim /usr/local/nagios/etc/nrpe.cfg

        #command[check_disk_root]=/usr/local/nagios/libexec/check_disk -w 20 -c 10 -p /dev/hba1

        command[check_disk_root]=/usr/local/nagios/libexec/check_disk -w 20 -c 10 -p /dev/hda1