There used to be a file in the /etc/init.d/ folder to restart ntopng.
The command that I used to use is:
sudo /etc/init.d/ntopng restart
But now with Ubuntu 18.04, that file is gone.
How do restart ntopng now?
The init.d script has been converted to a systemd unit which is now located in:
/etc/systemd/system
You restart ntopng now by:
sudo systemctl restart ntopng
Other (most) unit files are located in:
/lib/systemd/system/
More information about systemd unit files by looking at the man page:
man systemd.unit