What do the language presets actually change?

Each preset sets the FROM base image and the install/copy steps appropriate for that ecosystem, for example Node copies package*.json first and runs npm ci --omit=dev before copying the rest of the source, so Docker's layer cache is reused whenever only application code changes and dependencies don't.

Why does the non-root user step differ between presets?

Alpine-based images (Node, Go, static Nginx) use adduser/addgroup with the -S (system account) flag from Alpine's BusyBox utilities, while Debian/Ubuntu-based images (Python, Java, PHP) use the useradd/groupadd tools from shadow-utils. The generator picks the right pair automatically based on which base image your language preset uses.

How is the CMD or ENTRYPOINT built?

Whatever you type in the command field is split on whitespace and rendered as a JSON array, e.g. "node index.js" becomes CMD ["node", "index.js"], which is Docker's recommended exec form since it doesn't invoke a shell and handles signals (like SIGTERM) correctly.

Does this produce a multi-stage build?

No, this generates a single FROM ... single-stage Dockerfile. If you want a smaller production image built with a separate build stage, use the Multi-Stage Docker Builder tool instead.

Dockerfile Generator - Node, Python, Go, Java, PHP, Nginx

Overview

Introduction

Every language ecosystem has its own idiomatic Dockerfile shape, Node copies package.json before the rest of the source for layer caching, Go needs a build step, static sites just need a web server, and it's easy to forget one of these details when starting a new project.

This tool generates a single-stage Dockerfile from a language preset, handling the base image, install steps, and common options like EXPOSE, a non-root user, and CMD in one form.

What Is Dockerfile Generator?

A Dockerfile generator covering six presets: Node, Python, Go, Java, PHP, and a static-site Nginx image, each with its ecosystem's standard base image and dependency-install pattern.

Beyond the preset, you can set a custom WORKDIR, an EXPOSE port, toggle a non-root USER, and provide the CMD or ENTRYPOINT that starts your application.

How Dockerfile Generator Works

Choosing a preset fills in a FROM base image (e.g. node:20-alpine) and the copy/install steps for that ecosystem, ordered so dependency manifests are copied and installed before the rest of the source, preserving Docker's layer cache across rebuilds where only application code changed.

The non-root user toggle appends the correct addgroup/adduser or groupadd/useradd + USER lines depending on whether the preset's base image is Alpine or Debian-based. The command you type is parsed into a JSON array and emitted as CMD or ENTRYPOINT in exec form.

When To Use Dockerfile Generator

Use it when starting a new project and you want a correct, cache-friendly Dockerfile without looking up the right base image and install order for that language from scratch.

It's also useful as a quick reference for the non-root-user pattern for a given base image family, since the exact useradd/adduser flags differ between Alpine and Debian.

Often used alongside Multi-Stage Docker Builder, .dockerignore Generator and Docker Healthcheck Generator.

Features

Advantages

Orders COPY and install steps to maximize Docker layer cache reuse across rebuilds.
Automatically picks the correct user-creation commands for Alpine vs Debian-based images.
Emits CMD/ENTRYPOINT in the recommended JSON exec form rather than shell form, so signals like SIGTERM propagate correctly to your process.

Limitations

Only produces single-stage Dockerfiles; use the Multi-Stage Docker Builder for a separate build/runtime split.
Language presets are opinionated starting points (e.g. npm ci, not yarn or pnpm), you may need to adjust the install step for your exact toolchain.
Doesn't validate that the base image tag exists on Docker Hub or that your build context actually contains the files being copied.

Examples

A Node.js API with a non-root user

Input

language: node, workdir: /app, exposePort: 3000, nonRootUser: true, command: node server.js

Output

FROM node:20-alpine

WORKDIR /app

COPY package*.json ./
RUN npm ci --omit=dev
COPY . .

RUN addgroup -S app && adduser -S -G app appuser
USER appuser

EXPOSE 3000

CMD ["node", "server.js"]

The Alpine-based Node preset uses addgroup -S/adduser -S for the non-root user, and the command is rendered as a JSON exec-form array.

Best Practices & Notes

Best Practices

Always run as a non-root user in production images unless you have a specific reason your process needs root.
Keep dependency-manifest COPY steps separate from the full source COPY so Docker can cache the (usually slower) install step.
Pin the base image tag to a specific version (e.g. node:20-alpine, not node:latest) so builds are reproducible.

Developer Notes

Presets are stored as a small lookup table of { baseImage, installSteps, defaultWorkdir, defaultCommand } keyed by language, and the non-root-user step is chosen based on whether the language belongs to the Alpine-image family (node, go, static-nginx) or the Debian/Ubuntu family (python, java, php). CMD/ENTRYPOINT arguments are split on whitespace and serialized with JSON.stringify to produce a valid Dockerfile JSON array literal, matching Docker's exec form.

Dockerfile Generator Use Cases

Scaffolding a new project's Dockerfile in the language you're already using
Producing a quick reference for the correct non-root-user pattern for Alpine vs Debian base images
Generating a static-site Nginx Dockerfile for a prebuilt frontend build output

Common Mistakes

Running the container as root in production because the non-root toggle was left off.
Copying the entire source tree before installing dependencies, which busts the Docker layer cache on every source change.
Using shell-form CMD (CMD node server.js) instead of exec-form JSON array, which prevents signals from reaching your process directly.

Tips

Follow up with the Dockerignore Generator so your COPY . . step doesn't pull node_modules, .git, or .env into the build context.
Use the Docker Healthcheck Generator to add a HEALTHCHECK directive to the Dockerfile this tool produces.

Dockerfile Generator