Create a file for service your-service
touch /etc/systemd/system/your-service.service
Let’s assume you want to run docker container there. Put following text in the file:
[Unit]
Description=YourService
After=docker.service
Requires=docker.service
[Service]
TimeoutStartSec=0
Restart=always
ExecStartPre=-/usr/bin/docker stop %n
ExecStartPre=-/usr/bin/docker rm %n
ExecStart=/usr/bin/docker run -d -p 8080:8080/tcp --name %n your_docker_image
[Install]
WantedBy=multi-user.target
Here we first stop and delete the docker container. If it doesn’t exist we continue (there is a “-” in before the command).
Run
systemctl enable your-service
Commands
# prints the status
systemctl status your-service.service
# prepares the service, required before "start",
# also reloads the config if you changed the definition file
systemctl enable levels_tracker.service
# start service
systemctl start levels_tracker.service
# stop service
systemctl stop levels_tracker.service
Recipes
Specify working directory
[Service]
WorkingDirectory=/home/pi
Running python script from virtual environment
Just specify python interpreter from the environment:
ExecStart=<absolute path to your environment>/bin/python file_to_run.py
Environment variables
You can set environment variables that are used for your process
[Service]
Environment=VARIABLE=value
Now you can use it in the ExecStart command for example:
ExecStart=<absolute path to your environment>/bin/python file_to_run.py ${VARIABLE}
How to stdout of python-based service in syslog
Python buffers stdout. Therefore even if you have enable redirection of stdout to the syslog:
StandardOutput=syslog
You may see nothing in the logs. You should set environment variable for python PYTHONUNBUFFERED to see the results immediately:
#in your service file add to [Service] section:
Environment="PYTHONUNBUFFERED=1"
source: [here]
Probably better approach when you are allowed to install modules: https://medium.com/@trstringer/logging-to-systemd-in-python-45150662440a
See also:
[2] How To Use Systemctl to Manage Systemd Services and Units
[3] How to set up proper start/stop services
[4] https://github.com/torfsen/python-systemd-tutorial - great tutorial about how to set up systemd services. It also shows how to run a user services instead of system service. That requires less root privileges.