Running a Node.js application in the background

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.

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

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

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.

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

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.