Installation de nagios sur Ubuntu 20 04 

*********************Step 1 *********************************
sudo apt-get update
sudo apt-get install apache2
*********************Step 2 *********************************
sudo a2enmod auth_digest
sudo a2enmod authz_groupfile auth_digest
*********************Step 3 *********************************
sudo apt install nagios4 nagios-nrpe-plugin nagios-plugins-contrib
*********************Step 4 *********************************
sudo htdigest -c /etc/nagios4/htdigest.users Nagios4 nagiosadmin
*********************Step 5 *********************************
sudo vim /etc/apache2/conf-enabled/nagios4-cgi.conf
Comment Require IP line
Files start and closing tag only
Comment “Required all granted”
Uncomment “Require valid-user”
*********************Step 6 *********************************
Now, configure the CGI Authentication. Go to /etc/nagios4/cgi.cfg file and edit use_athentication from 0 to 1.
vim /etc/nagios4/cgi.cfg
*********************Step 7 *********************************
systemctl restart apache2
systemctl restart nagios4