Nagios : Install2026/06/10

	Install Nagios which is an enterprise open source monitoring system.
[1]	Install and start Apache httpd, refer to here.
[2]	Configure SSL/TLS setting, refer to here. (not required but recommended)
[3]	Install PHP, refer to here.
[4]	Install Nagios.

root@dlp:~#

apt -y install nagios4

[5]	Configure Nagios.

root@dlp:~#

vi /etc/nagios4/cgi.cfg

# line 76 : change
use_authentication=1

root@dlp:~#

vi /etc/apache2/conf-enabled/nagios4-cgi.conf

    # line 35 : change access permissions if you need
    Require ip  ::1/128 fc00::/7 fe80::/10 10.0.0.0/8 127.0.0.0/8 169.254.0.0/16 172.16.0.0/12 192.168.0.0/16
    # change
    <Files "*.cgi">
        AuthDigestDomain "Nagios4"
        AuthDigestProvider file
        AuthUserFile    "/etc/nagios4/htdigest.users"
        AuthGroupFile   "/etc/group"
        AuthName        "Nagios4"
        AuthType        Digest
        # comment out
        #Require all    granted
        # uncomment
        Require valid-user
    </Files>

root@dlp:~#

a2enmod cgid

Enabling module cgid.
To activate the new configuration, you need to run:
  systemctl restart apache2

root@dlp:~#

systemctl restart nagios4 apache2

root@dlp:~#

htdigest /etc/nagios4/htdigest.users "Nagios4" nagiosadmin

Adding user nagiosadmin in realm Nagios4
New password:     # set password for Nagios admin user
Re-type new password:

[6]	Access to the [(Nagios server's hostname or IP address)/nagios4/] from a client computer which is in the network allowed by Nagios. Then, Nagios start page is displayed.

[7]	You can view monitoring data by clicking on [Tactical Overview] etc. in the left menu, but you will need to authenticate as a Nagios administrative user.

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