Create the service definition file:

sudo nano /etc/systemd/system/kestrel-hellomvc.service

The following is an example service file for the app:

[Unit]
Description=Example .NET Web API App running on Ubuntu

[Service]
WorkingDirectory=/var/aspnetcore/hellomvc
ExecStart=/usr/bin/dotnet /var/aspnetcore/hellomvc/hellomvc.dll
Restart=always
# Restart service after 10 seconds if the dotnet service crashes:
RestartSec=10
SyslogIdentifier=dotnet-example
User=www-data
Environment=ASPNETCORE_ENVIRONMENT=Development

[Install]
WantedBy=multi-user.target

Save the file and enable the service.

systemctl enable kestrel-hellomvc.service

Start the service and verify that it's running.

systemctl start kestrel-hellomvc.service
systemctl status kestrel-hellomvc.service

You need to set WorkingDirectory - path to folder with your app and ExecStart - with path to your app dll. By default this is enough.