Daemonsize a service

To daemonize a Linux process means to run a program continuously in the background so that it detaches from your terminal and stays alive after you log out. [1, 2]

The industry-standard approach is to let systemd handle the service lifecycle. However, you can also do this directly via the command line or within your application code.

Method 1: Using systemd (Recommended)

This is the standard and most reliable method for modern Linux systems. [1, 2, 3]

1. Create a service configuration file:
   Open a new terminal and create a systemd configuration file:
   bash

   sudo nano /etc/systemd/system/my_python_daemon.service
   

   
   
2. Add the service definition:
   Paste the configuration template below. Replace the absolute paths, user, and script names with your project parameters:
   ini

   [Unit]
   Description=My Python Daemon App
   After=network.target
   
   [Service]
   Type=simple
   User=your_linux_username
   WorkingDirectory=/home/your_linux_username/my_project
   ExecStart=/home/your_linux_username/my_project/venv/bin/python /home/your_linux_username/my_project/main.py
   Restart=on-failure
   
   [Install]
   WantedBy=multi-user.target
   

   
   
3. Reload and start your new daemon:
   Run these commands sequentially to register, initiate, and verify your background process:
   bash

   sudo systemctl daemon-reload
   sudo systemctl enable my_python_daemon.service
   sudo systemctl start my_python_daemon.service
   sudo systemctl status my_python_daemon.service
   

   
   

Method 2: Using Supervisor (Alternative Process Manager)

If you do not have root (sudo) privileges to systemd, or prefer a dedicated application-level manager, use Supervisor. [1]

1. Add a program configuration:
   Create a configuration file within the Supervisor configuration directory:
   bash

   sudo nano /etc/supervisor/conf.d/my_python_daemon.conf
   

   
   
2. Add the tracking parameters:
   Provide the exact path to your venv binary inside the command argument:
   ini

   [program:my_python_daemon]
   command=/home/your_linux_username/my_project/venv/bin/python /home/your_linux_username/my_project/main.py
   directory=/home/your_linux_username/my_project
   autostart=true
   autorestart=true
   user=your_linux_username
   stderr_logfile=/var/log/my_python_daemon.err.log
   stdout_logfile=/var/log/my_python_daemon.out.log
   

   
   
3. Update Supervisor:
   Tell Supervisor to look for new configurations and start the daemon:
   bash

   sudo supervisorctl reread
   sudo supervisorctl update
   

   
   

Crucial Best Practices

• Avoid Relative Paths: Inside your daemonized Python scripts, avoid using relative file lookups like open("config.json"). Daemons often run relative to the root directory / or system folders unless explicitly specified by WorkingDirectory. [1]
• Reading Logs: Since the script runs invisibly in the background, you can inspect your print statements or unhandled tracebacks via the system journal:
  bash

  journalctl -u my_python_daemon.service -n 50 -f