Multistage Dockerfile Generator

Multistage Dockerfile generator - separate build and runtime

The multistage Dockerfile generator prepares two specialized stages for PHP, Node.js, Python or Go. Compilers and development dependencies stay in the build image, while the final stage receives only application code, artifacts and libraries required at runtime.

Choose a stack and supported image version, application name, working directory and port. The safe default runs the process as non-root, writes CMD in exec form and adds a runtime-specific health probe. For a simpler single-stage baseline, open the Dockerfile generator.

What actually enters the final image

Dependency cache and repeatable builds

The dependency manifest is copied before source code: composer.lock, package-lock.json, requirements.txt or go.sum. Docker can reuse the expensive installation layer after an application file changes. A lockfile change deliberately invalidates that cache and resolves a new package set.

The available tags name supported language lines and an Alpine or Slim variant; the generator never injects arbitrary text into FROM. A tag can still move at the publisher. For auditable production, replace every tested FROM tag with a digest and update digests through automated, reviewed pull requests.

Image security: non-root, secrets and a minimal runtime

File ownership and process user

PHP uses the existing www-data account, Node uses node, Python creates a system account named app, and Go does the same on Alpine. COPY --chown gives that account access without an expensive later chown -R. Disable non-root only for deliberate image debugging.

Non-root cannot repair unsafe host permissions. Do not mount docker.sock, avoid --privileged, and make only required directories writable. Once the image is ready, review its launch settings with the Docker Compose generator.

Secrets do not belong in ARG or ENV

The generator has no secret input and inserts no sample password. A .dockerignore should also exclude .env, .git, local caches and test output. Build a useful ignore list with the .gitignore generator.

Using and checking the generated Dockerfile

1. Choose the language. A preset selects a compatible tag and port; PHP-FPM remains on port 9000.
2. Match the module name, working directory and artifact path. The Node template assumes dist/server.js.
3. Save the output as Dockerfile and add a small .dockerignore.
4. Run docker build --pull -t app:test ., then scan the image and inspect its layer history.
5. Start the container without root, check logs and /health, then verify that SIGTERM stops the process cleanly.

A runtime-specific healthcheck

PHP-FPM does not speak HTTP, so its probe uses cgi-fcgi on port 9000. Node and Go call the BusyBox wget available in Alpine. Python performs HTTP with the standard-library urllib, avoiding a curl installation. Match /health to the application; for a background worker, replace it with a queue check or disable it.

Exec-form CMD and a custom command

Default commands are JSON arrays, allowing the application process to receive signals without an intermediate shell. A custom CMD is explicitly wrapped as ["sh","-c",...]; quotes are escaped and control characters rejected. This permits pipelines, but shell safety remains the image author's responsibility.

Before deployment, review writable directory modes with the chmod calculator and set CPU and memory limits in the orchestrator. A multistage build reduces attack surface but does not replace dependency scanning or regular base-image refreshes.

Frequently asked questions