Service files

Making a systemd service file

When you deploy your application on a server, you need to make sure the application runs uninterrupted. If the application crashes, you'd want it to automatically restart, and if the server experiences a power outage, you'd want the application to start immediately once power is restored.

SEE: https://blog.miguelgrinberg.com/post/running-a-flask-application-as-a-service-with-systemd

Useful: https://containersolutions.github.io/runbooks/posts/linux/debug-systemd-service-units/

$ sudo nano /etc/systemd/system/YOUR_NAME_OF_THE_APP.service

[Unit]
Description=<a description of your application>
After=network.target

[Service]
User=<username>
WorkingDirectory=<path to your app>
ExecStart=<app start command>
Restart=always

[Install]
WantedBy=multi-user.target

Here is an example:

 [Unit]
 Description=Bla Bla Bla made in Flask
 After=network.target
 
 [Service]
 User=YOUR_USERNAME
 WorkingDirectory=/YOUR/PATH/
 ExecStart=/YOUR/PATH/.venv/bin/flask --app NAME_OF_YOUR_PY_FILE run --port 51?? #DO NOT PUT .py AT THE END #PUT YOUR_PORT
 Restart=always
 
 [Install]
 WantedBy=multi-user.target

1st thing to do when your .service file is new or changed

$ sudo systemctl daemon-reload

Then in order:

$ sudo systemctl start YOUR_NAME_OF_THE_APP
$ sudo systemctl status YOUR_NAME_OF_THE_APP

When you see that it's working (checking its status, that it actually is running, etc...)

$ sudo systemctl enable YOUR_NAME_OF_THE_APP

Will make the "service" auto start when the pi restarts.

Additional commands:

$ sudo systemctl restart YOUR_NAME_OF_THE_APP
$ sudo systemctl stop YOUR_NAME_OF_THE_APP

To view the log file (errors):

$ sudo journalctl -u YOUR_NAME_OF_THE_APP -f

You can find documentation here:

https://www.freedesktop.org/software/systemd/man/latest/systemd.exec.html