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Background Apps

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):
  2. 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.

  • 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
  1. Using tmux (Linux/MacOS):
  2. 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
  1. Using systemd (Linux):
  2. 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
  1. Using & (Linux/MacOS):
  2. For a quick and simple way to run the Airflow scheduler in the background, just append & to the command:
airflow scheduler &
  1. Using Docker (If Airflow is running inside a container):
  2. 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:
  2. 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.

  • 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