Deploy and launch · Skill

Containerise an app with Docker

containerise-app-with-docker

Packages an app into a small, secure Docker image with a multi-stage Dockerfile - pinned slim base images, cached dependency layers, a .dockerignore, a non-root user and a health check - then builds and runs it locally. Use when the user wants to dockerise an app, write a Dockerfile, shrink a huge image, or run their app in a container.

Works with: Any AI Not yet model-tested; testing Jan 2027

View raw SKILL.mdInstall

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curl -fsSL --create-dirs 'https://theskillvault.ai/api/skills/containerise-app-with-docker/raw' -o ~/'.claude/skills/containerise-app-with-docker/SKILL.md' && curl -fsSL --create-dirs 'https://theskillvault.ai/api/skills/containerise-app-with-docker/files/LICENSE.txt' -o ~/'.claude/skills/containerise-app-with-docker/LICENSE.txt'

Cursor (this project)

curl -fsSL --create-dirs 'https://theskillvault.ai/api/skills/containerise-app-with-docker/raw' -o '.cursor/skills/containerise-app-with-docker/SKILL.md' && curl -fsSL --create-dirs 'https://theskillvault.ai/api/skills/containerise-app-with-docker/files/LICENSE.txt' -o '.cursor/skills/containerise-app-with-docker/LICENSE.txt'

Codex and other Agent Skills tools (this project)

curl -fsSL --create-dirs 'https://theskillvault.ai/api/skills/containerise-app-with-docker/raw' -o '.agents/skills/containerise-app-with-docker/SKILL.md' && curl -fsSL --create-dirs 'https://theskillvault.ai/api/skills/containerise-app-with-docker/files/LICENSE.txt' -o '.agents/skills/containerise-app-with-docker/LICENSE.txt'

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{
  "mcpServers": {
    "theskillvault": {
      "url": "https://theskillvault.ai/mcp"
    }
  }
}

A container packs your app and everything it needs into one image that runs the same everywhere. Multi-stage builds keep that image small.

When to use

  • A host asks for a Docker image or a Dockerfile.
  • "It works on my machine" keeps biting you.
  • Your image is over 1 GB and slow to deploy.

Steps

  1. Add a .dockerignore listing node_modules, .git, .env*, build output and logs.
  2. Pick an official slim base with an exact tag, such as node:22-slim or python:3.12-slim.
  3. Stage one ("deps"): copy only the lockfile and manifest, then install dependencies. This layer caches.
  4. Stage two ("build"): copy the source and run the build.
  5. Final stage: start from the slim base again and copy only the built output and production dependencies.
  6. Create or use a non-root user and switch to it with USER.
  7. Set NODE_ENV=production (or the equivalent), EXPOSE the port and add a HEALTHCHECK if your host uses it.
  8. Build and run: docker build -t myapp . then docker run --env-file .env -p 3000:3000 myapp.
  9. Check the size with docker images myapp and scan it with docker scout cves myapp or Trivy.
FROM node:22-slim AS deps
WORKDIR /app
COPY package.json package-lock.json ./
RUN npm ci

FROM deps AS build
COPY . .
RUN npm run build && npm prune --omit=dev

FROM node:22-slim
WORKDIR /app
ENV NODE_ENV=production
COPY --from=build --chown=node:node /app/node_modules ./node_modules
COPY --from=build --chown=node:node /app/dist ./dist
USER node
EXPOSE 3000
CMD ["node", "dist/server.js"]

Gotchas

  • Never COPY .env or bake API keys into an image. Anyone with the image can read them. Pass secrets at run time.
  • Copying all source before installing dependencies breaks caching, so every build reinstalls.
  • latest tags change under you. Pin versions.
  • Alpine images are small but can break native modules. Slim images are the safer default.

Portability

Works with any language: swap the install and build commands for pip, Go or Maven. If you use Podman instead of Docker, the same Dockerfile works.

Example prompt

"Write a production Dockerfile for my Node API that is small, runs as non-root and keeps secrets out of the image."

Done when

  • The image builds and the app runs with docker run.
  • It runs as a non-root user and contains no .env file or keys.
  • The final image is far smaller than a single-stage build.

---

Adapted from "multi-stage-dockerfile" in github/awesome-copilot (MIT, Copyright GitHub, Inc.). See LICENSE.txt.

Bundled files

Licence

Adapted from GitHub awesome-copilot contributors (multi-stage-dockerfile) (Copyright GitHub, Inc.), MIT License. Adapted by TheSkillVault: turned a bullet checklist into numbered steps with an original Node example, a .dockerignore and run commands; added secrets handling, gotchas and done-when.

Licence: MIT License. Attribution when you reuse it: Based on work by GitHub awesome-copilot contributors (multi-stage-dockerfile) (Copyright GitHub, Inc., MIT License), https://github.com/github/awesome-copilot/tree/5269f7ea2d6c3a9bfda5ed878b6726cf509121fd/skills/multi-stage-dockerfile; adapted by TheSkillVault, https://theskillvault.ai