Implementation:Langgenius Dify Copy And Start

Knowledge Sources	Langgenius_Dify
Domains	Frontend, Build_Tools
Last Updated	2026-02-12 07:00 GMT

Overview

Production startup script that copies required static assets into the Next.js standalone output directory and then launches the production server.

Description

copy-and-start.mjs is a Node.js ESM script used as a replacement for next start in production deployments that use Next.js standalone output mode. The Next.js standalone build does not include the .next/static and public directories, so this script copies them into the standalone directory before starting the server.

The script performs two phases:

1. Asset Copy Phase -- Iterates over a configured list of directory pairs and copies each source directory into the standalone output tree:
   • .next/static is copied to .next/standalone/.next/static
   • public is copied to .next/standalone/public

   Parent directories are created automatically. If a required source directory does not exist, the script exits with code 1.

1. Server Start Phase -- Spawns the Node.js process running .next/standalone/server.js with:
   • PORT from npm_config_port, PORT environment variable, or defaults to 3000
   • HOSTNAME from npm_config_host, HOSTNAME environment variable, or defaults to 0.0.0.0

   The server process inherits stdio and the script propagates its exit code.

Usage

Use this script in Docker containers or production environments where Next.js standalone output is deployed. It replaces the standard next start command to handle the asset copying that standalone mode requires.

Code Reference

Source Location

• Repository: Langgenius_Dify
• File: web/scripts/copy-and-start.mjs
• Lines: 1-115

Signature

const DIRS_TO_COPY = [
  { src: '.next/static',  dest: '.next/standalone/.next/static' },
  { src: 'public',        dest: '.next/standalone/public' },
]
const SERVER_SCRIPT_PATH = '.next/standalone/server.js'

const pathExists = async (path) => { ... }
const copyDir = async (src, dest) => { ... }
const copyAllDirs = async () => { ... }
const main = async () => { ... }

Import

// CLI script - run directly
node web/scripts/copy-and-start.mjs

I/O Contract

Inputs

Name	Type	Required	Description
.next/static	directory	Yes	Next.js compiled static assets (CSS, JS chunks, media) produced by next build
public	directory	Yes	Public static files (favicon, images, robots.txt, etc.)
.next/standalone/server.js	file	Yes	The standalone server entry point produced by next build with output: 'standalone'
PORT	env variable	No	Server port; defaults to 3000
HOSTNAME	env variable	No	Server hostname; defaults to 0.0.0.0

Outputs

Name	Type	Description
.next/standalone/.next/static	directory	Copied static assets inside standalone directory
.next/standalone/public	directory	Copied public assets inside standalone directory
Running server process	process	Node.js server listening on the configured host and port
exit code 0	number	Server exited normally
exit code 1	number	Missing build artifacts or server startup failure

Usage Examples

Start production server (default port 3000)

node web/scripts/copy-and-start.mjs

Start with custom port and host

PORT=8080 HOSTNAME=127.0.0.1 node web/scripts/copy-and-start.mjs

Use in Dockerfile

CMD ["node", "scripts/copy-and-start.mjs"]

Related Pages

• Principle:Langgenius_Dify_Production_Deployment
• Principle:Langgenius_Dify_Docker_Infrastructure