Install Nagios Server on Oracle Linux 9

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In this guide, you will learn how to install Nagios Server on Oracle Linux 9. Nagios provides enterprise-class Open Source IT monitoring, network monitoring, server and applications monitoring.

Install Nagios Server on Oracle Linux 9

To install Nagios Server on Oracle Linux 9, follow through the steps below;

Run System Update

Resynchronize your system packages to their latest versions.

dnf update

Install Required Build Tools

The default Oracle Linux repositories do not provide Nagios Core packages. As a result, in this guide, we are going to build Nagios Core from the source code. As such there are packages and build tools that you need to install. Run the command below to install them.

dnf install gcc glibc glibc-common perl httpd php php-cli php-fpm wget net-snmp gd gd-devel openssl openssl-devel

Download Nagios Core Source Code

Navigate to the Nagios Core downloads page and grab the latest Nagios core source code. Nagios v4.4.6 is the current stable release as of this guide.

Get the latest stable release version number and substitute the value of the $VER variable below and use wget to download the file.

VER=4.4.7
wget https://assets.nagios.com/downloads/nagioscore/releases/nagios-$VER.tar.gz

Extract the Nagios Source Code

Once the Nagios source is downloaded, extract it by running the command;

tar xzf nagios-$VER.tar.gz

Installing Nagios Core

Next, navigate to the Nagios source code directory.

cd nagios-$VER/

Configure Nagios Core on Oracle Linux 9

Run the configuration script to adapt Nagios to your system and check if all required dependencies and build tools are in place.

./configure

If the configuration is successful, you will be provided with the summary;

Creating sample config files in sample-config/ ...


*** Configuration summary for nagios 4.4.7 2022-04-14 ***:

 General Options:
 -------------------------
        Nagios executable:  nagios
        Nagios user/group:  nagios,nagios
       Command user/group:  nagios,nagios
             Event Broker:  yes
        Install ${prefix}:  /usr/local/nagios
    Install ${includedir}:  /usr/local/nagios/include/nagios
                Lock file:  /run/nagios.lock
   Check result directory:  /usr/local/nagios/var/spool/checkresults
           Init directory:  /lib/systemd/system
  Apache conf.d directory:  /etc/httpd/conf.d
             Mail program:  /bin/mail
                  Host OS:  linux-gnu
          IOBroker Method:  epoll

 Web Interface Options:
 ------------------------
                 HTML URL:  http://localhost/nagios/
                  CGI URL:  http://localhost/nagios/cgi-bin/
 Traceroute (used by WAP):  


Review the options above for accuracy.  If they look okay,
type 'make all' to compile the main program and CGIs.

Compile Nagios Core on Oracle Linux 9

Next, proceed to compile Nagios Main program and CGIs.

make all

If the main program and CGIs compiled without any errors, proceed to install Nagios Server on Oracle Linux, and its configurations.

Sample compilation output;

*** Compile finished ***

If the main program and CGIs compiled without any errors, you
can continue with testing or installing Nagios as follows (type
'make' without any arguments for a list of all possible options):

  make test
     - This runs the test suite

  make install
     - This installs the main program, CGIs, and HTML files

  make install-init
     - This installs the init script in /lib/systemd/system

  make install-daemoninit
     - This will initialize the init script
       in /lib/systemd/system

  make install-groups-users
     - This adds the users and groups if they do not exist

  make install-commandmode
     - This installs and configures permissions on the
       directory for holding the external command file

  make install-config
     - This installs *SAMPLE* config files in /usr/local/nagios/etc
       You'll have to modify these sample files before you can
       use Nagios.  Read the HTML documentation for more info
       on doing this.  Pay particular attention to the docs on
       object configuration files, as they determine what/how
       things get monitored!

  make install-webconf
     - This installs the Apache config file for the Nagios
       web interface

  make install-exfoliation
     - This installs the Exfoliation theme for the Nagios
       web interface

  make install-classicui
     - This installs the classic theme for the Nagios
       web interface


*** Support Notes *******************************************

If you have questions about configuring or running Nagios,
please make sure that you:

     - Look at the sample config files
     - Read the documentation on the Nagios Library at:
           
Nagios Library
before you post a question to one of the mailing lists. Also make sure to include pertinent information that could help others help you. This might include: - What version of Nagios you are using - What version of the plugins you are using - Relevant snippets from your config files - Relevant error messages from the Nagios log file For more information on obtaining support for Nagios, visit:
Home
************************************************************* Enjoy.

Create Nagios User and Group

Nagios runs as non-privileged nagios user. As such, you need to create a Nagios system user and group.

make install-groups-users

Add Apache user to the Nagios group.

usermod -aG nagios apache

Install Nagios Core on Oracle Linux 9

Install Nagios main program, CGIs, and HTML files.

make install

Install Nagios Systemd Service

Install Nagios Systemd initialization scripts.

make install-daemoninit

Install Nagios Commands

Install and configure the external command file as well as the permissions on the directory holding the external commands file.

make install-commandmode

Install Nagios Configuration Files

Install Nagios Sample configuration file.

make install-config

This command installs Nagios sample configuration files in /usr/local/nagios/etc.

Install Nagios Apache Configuration files

Next, install the Apache HTTP server configuration files for Nagios.

make install-webconf

Setup Nagios Apache Authentication

To setup Nagios Web authentication, you need to create an Apache user for authentication. This can be done using the htpasswd command.

htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

The user, nagiosadmin, is used by default.

If you need to use a different user, you need to replace all the occurences of nagiosadmin on the /usr/local/nagios/etc/cgi.cfg file with the user you created.

For example, if you use a user like monadmin, replace nagiosadmin as shown below.

sed -i 's/nagiosadmin/monadmin/g' /usr/local/nagios/etc/cgi.cfg

If you also want to use a different authentication user file instead of, /usr/local/nagios/etc/htpasswd.users, ensure you edit the Nagios Apache configuration file, /etc/httpd/conf.d/nagios.conf and change the value of AuthUserFile.

Set the ownership of the Nagios Apache authentication configuration file to web-server user, apache.

chown apache:apache /usr/local/nagios/etc/htpasswd.users

Adjust the file permissions appropriately such that the owner (apache) have read write access, the group has read access.

chmod 640 /usr/local/nagios/etc/htpasswd.users

Start Apache Web server

Once you are done with configuration, start and enable Apache to run on system boot.

systemctl enable httpd --now

If firewallD is running on your system, be sure to enable external access to Apache.

firewall-cmd --add-port=80/tcp --permanent
firewall-cmd --reload

Start Nagios Core service

Start and enable Nagios service to run on system boot.

systemctl enable nagios --now

To check the status

systemctl status nagios
● nagios.service - Nagios Core 4.4.7
     Loaded: loaded (/usr/lib/systemd/system/nagios.service; enabled; vendor preset: disabled)
     Active: active (running) since Wed 2022-09-14 19:25:36 EAT; 2min 37s ago
       Docs: https://www.nagios.org/documentation
    Process: 775 ExecStartPre=/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg (code=exited, status=0/SUCCESS)
    Process: 782 ExecStart=/usr/local/nagios/bin/nagios -d /usr/local/nagios/etc/nagios.cfg (code=exited, status=0/SUCCESS)
   Main PID: 790 (nagios)
      Tasks: 6 (limit: 15848)
     Memory: 19.4M
        CPU: 101ms
     CGroup: /system.slice/nagios.service
             ├─790 /usr/local/nagios/bin/nagios -d /usr/local/nagios/etc/nagios.cfg
             ├─792 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
             ├─793 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
             ├─794 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
             ├─795 /usr/local/nagios/bin/nagios --worker /usr/local/nagios/var/rw/nagios.qh
             └─810 /usr/local/nagios/bin/nagios -d /usr/local/nagios/etc/nagios.cfg

Sep 14 19:25:36 localhost nagios[790]: wproc: Registry request: name=Core Worker 792;pid=792
Sep 14 19:25:36 localhost nagios[790]: wproc: Registry request: name=Core Worker 793;pid=793
Sep 14 19:25:36 localhost nagios[790]: Successfully launched command file worker with pid 810
Sep 14 19:25:36 localhost.localdomain nagios[790]: HOST ALERT: localhost;DOWN;SOFT;1;(No output on stdout) stderr: execvp(/usr/local/nagios/libexec/check_ping, ...) failed>
Sep 14 19:26:13 localhost.localdomain nagios[790]: SERVICE ALERT: localhost;Current Load;CRITICAL;HARD;1;(No output on stdout) stderr: execvp(/usr/local/nagios/libexec/che>
Sep 14 19:26:36 localhost.localdomain nagios[790]: HOST ALERT: localhost;DOWN;SOFT;2;(No output on stdout) stderr: execvp(/usr/local/nagios/libexec/check_ping, ...) failed>
Sep 14 19:26:51 localhost.localdomain nagios[790]: SERVICE ALERT: localhost;Current Users;CRITICAL;HARD;1;(No output on stdout) stderr: execvp(/usr/local/nagios/libexec/ch>
Sep 14 19:27:28 localhost.localdomain nagios[790]: SERVICE ALERT: localhost;HTTP;CRITICAL;HARD;1;(No output on stdout) stderr: execvp(/usr/local/nagios/libexec/check_http,>
Sep 14 19:27:36 localhost.localdomain nagios[790]: HOST ALERT: localhost;DOWN;SOFT;3;(No output on stdout) stderr: execvp(/usr/local/nagios/libexec/check_ping, ...) failed>
Sep 14 19:28:06 localhost.localdomain nagios[790]: SERVICE ALERT: localhost;PING;CRITICAL;HARD;1;(No output on stdout) stderr: execvp(/usr/local/nagios/libexec/check_ping

You can check Nagios logs at /usr/local/nagios/var/nagios.log.

If the service fails with the error;

Caught SIGSEGV, shutting down...
  • Either check to ensure that your system is not running out of memory
  • or disable updates check by editing the file, /usr/local/nagios/etc/nagios.cfg and setting the value of check_for_updates to 0 and restart the service.

If for some reasons you want to configure Apache to server Nagios on a different port apart from port 80, then insert the following lines in the Nagios Apache configuration file, /etc/httpd/conf.d/nagios.conf.

Insert the lines below at the top of the configuration file;

Listen 8888
<VirtualHost *:8888>

And the line below at the end of the configuration file;

</VirtualHost>

Such that the configuration file looks like below, without comment lines;

grep -Ev "^#|^$" /etc/httpd/conf.d/nagios.conf
Listen 8888
<VirtualHost *:8888>
ScriptAlias /nagios/cgi-bin "/usr/local/nagios/sbin"
<Directory "/usr/local/nagios/sbin">
   Options ExecCGI
   AllowOverride None
   <IfVersion >= 2.3>
      <RequireAll>
         Require all granted
         AuthName "Nagios Access"
         AuthType Basic
         AuthUserFile /usr/local/nagios/etc/htpasswd.users
         Require valid-user
      </RequireAll>
   </IfVersion>
   <IfVersion < 2.3>
      Order allow,deny
      Allow from all
      AuthName "Nagios Access"
      AuthType Basic
      AuthUserFile /usr/local/nagios/etc/htpasswd.users
      Require valid-user
   </IfVersion>
</Directory>
Alias /nagios "/usr/local/nagios/share"
<Directory "/usr/local/nagios/share">
   Options None
   AllowOverride None
   <IfVersion >= 2.3>
      <RequireAll>
         Require all granted
         AuthName "Nagios Access"
         AuthType Basic
         AuthUserFile /usr/local/nagios/etc/htpasswd.users
         Require valid-user
      </RequireAll>
   </IfVersion>
   <IfVersion < 2.3>
      Order allow,deny
      Allow from all
      AuthName "Nagios Access"
      AuthType Basic
      AuthUserFile /usr/local/nagios/etc/htpasswd.users
      Require valid-user
   </IfVersion>
</Directory>
</VirtualHost>

Check Apache configuration syntax;

httpd -t

If SELinux is running, execute the commands below to allow Apache to bind to the new port;

setsebool -P nis_enabled 1

Restart both Nagios service and Apache service;

systemctl restart httpd nagios

Open new port on firewall;

firewall-cmd --add-port=8888/tcp --permanent
firewall-cmd --reload

Accessing Nagios on Oracle Linux 9

You can now access your Nagios server from the browser using the address http://<server-IP or HOSTNAME>/nagios.

If you changed the port, access it as http://<server-IP or HOSTNAME>:PORT/nagios

You will be prompted to enter username and password created above to login.

Enter the authentication credentials and proceed to Nagios web interface.

Install Nagios Server on Oracle Linux 9

You have successfully installed Nagios on Oracle Linux 9.

You can now start monitoring your end points with Nagios.

If you can check, even the status of the localhost and services are down since no Nagios plugins are installed by default.

Install Nagios Server on Oracle Linux 9
Install Nagios Server on Oracle Linux 9

To start to monitor your hosts with Nagios, you need to install Nagios plugins and the NRPE plugins.

Install Nagios Plugins on Oracle Linux

Once you install plugins, services should be ok now;

nagios plugins monitoring

That marks the end of our tutorial on how to install Nagios Server on Oracle Linux 9.

You can also check other Nagios Tutorials by following the links below;

Monitor SSL/TLS Certificates Expiry with Nagios

Configure Nagios Email Notification Using Gmail

Add Hosts to Nagios Server For Monitoring

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