@Jean,

To restart LibreNMS, you need to restart the web server and the services it relies on.

sudo systemctl restart apache2
OR
sudo systemctl restart nginx
sudo systemctl restart php-fpm

@jj

Correct, this depends on your PHP version. If you have PHP 7.2, then use fastcgi_pass unix:/var/run/php-fpm/php7.2-fpm.sock; or if you have PHP 7.0, use fastcgi_pass unix:/var/run/php-fpm/php7.0-fpm.sock; and so on. Many thanks for sharing this.

@lulian

Many thanks for the useful addition.