Serve Nagios 3 as a standalone Apache site

By default Nagios 3 is served as an alias, your-domain.com/nagios3. To serve it as a standalone site:

1. Disable the default config: a2disconf nagios3

2. Link the Nagios Apache config as a site: ln -s /etc/nagios3/apache2.conf /etc/apache2/sites-enabled/your-domain.com.conf

3. Edit that file to look like this:

   <VirtualHost *:80>
           ServerAdmin webmaster@example.com
           ServerName nagios.example.com
   
           ScriptAlias /cgi-bin/nagios3 /usr/lib/cgi-bin/nagios3/
   
           Alias /stylesheets /etc/nagios3/stylesheets/
           Alias / /usr/share/nagios3/htdocs/
   
           DocumentRoot /usr/share/nagios3/htdocs/
   
           <DirectoryMatch (/usr/share/nagios3/htdocs|/usr/lib/cgi-bin/nagios3|/etc/nagios3/stylesheets)>
                   Options FollowSymLinks
   
                   DirectoryIndex index.php index.html
   
                   AllowOverride AuthConfig
                   Order Allow,Deny
                   Allow From All
   
                   AuthName "Nagios Access"
                   AuthType Basic
                   AuthUserFile /path/to/nagios3/htpasswd.users
                   require valid-user
           </DirectoryMatch>
   
           <Directory /usr/share/nagios3/htdocs>
                   Options +ExecCGI
           </Directory>
   
           ErrorLog ${APACHE_LOG_DIR}/nagios.example.com-error.log
           LogLevel warn
           CustomLog ${APACHE_LOG_DIR}/nagios.example.com-access.log combined
   </VirtualHost>

4. In /etc/nagios3/cgi.cfg, change url_html_path from /nagios3 to /.

5. Restart Apache: service apache2 restart