How to Run a Node.js Web Application as a Linux Daemon

A daemon is a process that runs continuously in the background. This guide shows how to start a web application as a daemon.

1. Problem Origin

After writing a web app, you need to launch it so it stays running. A simple Node.js server (server.js) with six lines looks like this:

var http = require('http'); http.createServer(function(req, res) { res.writeHead(200, {'Content-Type': 'text/plain'}); res.end('Hello World'); }).listen(5000);

Running it with $ node server.js works, but when you close the terminal the process exits.

2. Foreground vs. Background Jobs

A foreground job occupies the terminal. Adding & at the end of a command makes it a background job. You can also suspend a foreground job with Ctrl+Z and resume it with bg.

Background jobs inherit stdout and stderr but not stdin.

3. SIGHUP Signal

When a session ends, the shell may send a SIGHUP signal to its child processes, causing them to exit. The huponexit shell option controls this. Check its value with:

$ shopt | grep huponexit

On most Linux systems it is off, so background jobs usually survive session termination.

4. The disown Command

To ensure a background job is not affected by SIGHUP, use disown to remove it from the job table:

$ disown # remove the most recent background job

$ disown -r # remove all background jobs

$ disown -a # remove all jobs but keep them alive

$ disown -h # keep jobs but prevent SIGHUP

$ disown %2 # remove job with ID 2

After disowning, jobs will no longer list the process.

5. Standard I/O Redirection

If a background task still interacts with standard I/O, it will terminate when the session ends. Redirect its output:

$ node server.js > stdout.txt 2> stderr.txt

This prevents the process from hanging.

6. The nohup Command nohup makes a process ignore SIGHUP, closes stdin, and redirects output to nohup.out:

$ nohup node server.js

Combine with & to run it in the background.

7. Terminal Multiplexers: Screen and Tmux

Screen and Tmux let you create detachable sessions. Example with Screen:

$ screen

$ node server.js

Detach with Ctrl+A D, later reattach with $ screen -r. Use -S name to name sessions.

Tmux usage:

$ tmux

$ node server.js

$ tmux detach

$ tmux attach

Both tools allow you to keep services running after logout.

8. Node Process Managers

forever keeps a Node process alive and can restart it:

$ forever server.js

$ forever start app.js

$ forever stop Id

$ forever restart Id

$ forever -w server.js # watch files

$ forever -m 5 server.js # max restarts

$ forever list

nodemon watches files during development and restarts on changes:

$ nodemon server.js

$ nodemon --watch app --watch libs server.js

pm2 offers advanced process management, clustering, logging, and monitoring:

$ pm2 start app.js

$ pm2 start app.js -i max # cluster mode

$ pm2 list

$ pm2 stop 0

$ pm2 restart 0

$ pm2 delete 0

$ pm2 save

$ pm2 monit

$ pm2 logs

$ pm2 dump

$ pm2 kill

$ pm2 resurect

$ pm2 web # web UI at http://localhost:9615

9. Systemd

Beyond third‑party tools, Linux provides systemd as a native daemon manager. It integrates directly with the kernel, offering high performance and powerful features for managing services.