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Running a Node.js application in the background

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Method 1: Using nohup

nohup stands for ‘no hang up’ and allows the process to continue running after you log out from the shell. 
nohup node index.js &
  • nohup: Command to run the process immune to hangups.
  • node index.js: Your Node.js application entry point.
  • &: Runs the process in the background.

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Method 2: Using screen

screen is a terminal multiplexer that allows you to run multiple terminal sessions from a single SSH session.
  1. Start a new screen session: 
    screen -S my-node-app
  2. Run your Node.js application: 
    node index.js
  3. Detach from the screen session by pressing Ctrl + A, then D.
  4. To reattach to the session later: 
    screen -r my-node-app

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Method 3: Using tmux

tmux is another terminal multiplexer, similar to screen.
  1. Start a new tmux session: 
    tmux new -s my-node-app
  2. Run your Node.js application: 
    node index.js
  3. Detach from the tmux session by pressing Ctrl + B, then D.
  4. To reattach to the session later: 
    tmux attach -t my-node-app

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Method 4: Using pm2

pm2 is a process manager specifically designed for Node.js applications.
  1. Install pm2 globally: 
    npm install -g pm2
  2. Start your Node.js application with pm2: 
    pm2 start index.js
  3. To list all running applications: 
    pm2 list
  4. To save the process list and resurrect them on reboot: 
    pm2 save
pm2 startup
This method ensures that your application will restart automatically if it crashes and can be configured to start on server reboot.

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Method 5: Using Systemd

Create a systemd service file to manage your Node.js application.
  1. Create a new service file for your application: 
    sudo nano /etc/systemd/system/my-node-app.service
  2. Add the following content to the service file: 
    [Unit]
Description=My Node.js Application
After=network.target

[Service]
ExecStart=/usr/bin/node /path/to/your/index.js
Restart=always
User=your-username
Group=your-groupname
Environment=PATH=/usr/bin:/usr/local/bin
Environment=NODE_ENV=production
WorkingDirectory=/path/to/your/application

[Install]
WantedBy=multi-user.target
  3. Reload systemd to apply the new service: 
    sudo systemctl daemon-reload
  4. Start your service: 
    sudo systemctl start my-node-app
  5. Enable the service to start on boot: 
    sudo systemctl enable my-node-app

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Summary

Each method has its own advantages:
  • nohup is simple and easy.
  • screen and tmux are great for interactive processes.
  • pm2 offers advanced features for managing and monitoring Node.js applications.
  • systemd integrates well with the system’s init process and is robust for production environments.
Choose the method that best fits your needs and the environment where your application will run.