How to Run a Service in the Background on Linux and Check if It’s Running

In this article, I will show you how to run a service in the background. I’ve used Apache Airflow as an example, but you can apply these methods to other services as well.

Running a Service in the Background

1. Using nohup (Linux/MacOS):
   • The nohup command allows you to run the Airflow scheduler in the background and ensures it continues running even after you close the terminal.

   nohup airflow scheduler > scheduler.log 2>&1 &
   

   • Here, nohup keeps the process running, > scheduler.log 2>&1 saves the output to a log file, and & runs it in the background.
2. Using screen (Linux/MacOS):
   • screen is a terminal multiplexer that lets you start a terminal session that you can detach from and reattach to later.

   screen -S airflow-scheduler
   airflow scheduler
   

   • After starting the scheduler, detach the screen session by pressing Ctrl + A, then D. To reattach to the session, use:

   screen -r airflow-scheduler
   

3. Using tmux (Linux/MacOS):
   • tmux is similar to screen, providing another way to manage terminal sessions that you can detach and reattach to.

   tmux new -s airflow-scheduler
   airflow scheduler
   

   • Detach from the session with Ctrl + B, then D. Reattach with:

   tmux attach -t airflow-scheduler
   

4. Using systemd (Linux):
   • To manage the Airflow scheduler as a service, you can create a systemd service file. This method is more permanent and reliable.

   Create a file at /etc/systemd/system/airflow-scheduler.service with the following content:

   [Unit]
   Description=Airflow Scheduler
   After=network.target
   
   [Service]
   ExecStart=/usr/local/bin/airflow scheduler
   Restart=always
   User=airflow
   Group=airflow
   StandardOutput=syslog
   StandardError=syslog
   SyslogIdentifier=airflow-scheduler
   
   [Install]
   WantedBy=multi-user.target
   

   • Then enable and start the service:

   sudo systemctl enable airflow-scheduler
   sudo systemctl start airflow-scheduler
   

5. Using & (Linux/MacOS):
   • For a quick and simple way to run the Airflow scheduler in the background, just append & to the command:

   airflow scheduler &
   

6. Using Docker (If Airflow is running inside a container):
   • If you’re using Docker, you can run the Airflow scheduler in detached mode using the following command:

   docker run -d --name airflow-scheduler apache/airflow:latest scheduler
   

   • This command will start the scheduler in the background inside the Docker container.

Checking if a Service is Running

1. Checking the Airflow Scheduler:
   • To see if the Airflow scheduler is running, use the ps command:

   ps aux | grep 'airflow scheduler'
   

   • This command will list the running processes, including the Airflow scheduler if it’s active.
2. Checking Apache Web Server:
   • For Apache, which is a widely used web server, you can check its status with:

   sudo systemctl status apache2
   

   • If Apache is running, you’ll see “active (running)” in the status output.

Conclusion

So, the popular commands to run services in the background in linux like os are:nohup, screen, tmux and systemctl