# dockerfile-optimise

A skill with 48 rules from official Docker docs: layer caching, multi-stage builds, security. Useful when writing or refactoring Dockerfiles.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 344 installs · ★ 218
- Author: pproenca
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/pproenca/dot-skills/tree/HEAD/skills/.experimental/dockerfile-optimise/SKILL.md
- Updated: 2026-08-15
- HTML: https://affpapa.org/en/nevibecode/skills/dockerfile-optimise

## What it does

The skill hands your agent a rule set for Dockerfiles, sourced from official Docker documentation. There are 48 rules across 8 categories, ordered by impact: layer caching and multi-stage builds are marked critical, base image selection and secrets handling are high, then dependency management, instruction patterns and quality checks. Each rule carries a prefix like `cache-` or `sec-`, which makes them easy to look up.

Reference files hold the explanation and code examples for every rule. The agent reads them when it writes a new Dockerfile, scans an existing one for anti-patterns, or sets up a build in CI. Triggers fire on multi-stage work, build cache, image size and container hardening.

One catch: several BuildKit features (cache mounts, secret mounts, heredocs, `COPY --link`) need the syntax directive at the top of the Dockerfile. Without it those rules won't do anything at build time. Worth installing if you edit Dockerfiles by hand or through an agent on a regular basis.

## Requirements
- Works with: Docker

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add pproenca/dot-skills --skill dockerfile-optimise -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/dockerfile-optimise/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/dockerfile-optimise/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add pproenca/dot-skills --skill dockerfile-optimise -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/dockerfile-optimise/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add pproenca/dot-skills --skill dockerfile-optimise -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/dockerfile-optimise/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install pproenca/dot-skills dockerfile-optimise
```

2. **Manually: put the files in place**
- File: `.github/skills/dockerfile-optimise/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add pproenca/dot-skills --skill dockerfile-optimise -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/pproenca/dot-skills --path skills/.experimental/dockerfile-optimise
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/dockerfile-optimise/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add pproenca/dot-skills --skill dockerfile-optimise -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/pproenca/dot-skills/tree/HEAD/skills/.experimental/dockerfile-optimise/SKILL.md

## When to use it
- order layers so the cache survives code edits
- split build and runtime into separate stages
- keep secrets out of ARG and ENV
- wire up a cache mount for npm, pip or apt
- scan a Dockerfile for anti-patterns before merge

## Example prompts
- Rewrite my Dockerfile so dependencies are copied in a layer before the source code
- Split this Dockerfile into build and runtime stages and copy only artifacts into the final image
- Check the Dockerfile for leaked secrets and add a non-root user

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 95e7b46e46a8bd67.

BEGIN THIRD-PARTY FILE 95e7b46e46a8bd67
```text
---
name: dockerfile-optimise
description: Dockerfile optimization guidelines from official Docker documentation. This skill should be used when writing, reviewing, or refactoring Dockerfiles to ensure optimal build time, image size, security, and robustness. Triggers on tasks involving Dockerfile creation, Docker image builds, container optimization, multi-stage builds, build cache, or Docker security hardening.
---

# Dockerfile Optimization Best Practices

Comprehensive Dockerfile optimization guide sourced exclusively from official Docker documentation. Contains 48 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.

## When to Apply

Reference these guidelines when:
- Writing new Dockerfiles or modifying existing ones
- Optimizing Docker build times (layer caching, cache mounts, context management)
- Reducing Docker image size (multi-stage builds, minimal base images)
- Hardening container security (secret mounts, non-root users, attestations)
- Setting up CI/CD pipelines with Docker builds
- Reviewing Dockerfiles for anti-patterns

## Rule Categories by Priority

| Priority | Category | Impact | Prefix |
|----------|----------|--------|--------|
| 1 | Layer Caching & Ordering | CRITICAL | `cache-` |
| 2 | Multi-Stage Builds | CRITICAL | `stage-` |
| 3 | Base Image Selection | HIGH | `base-` |
| 4 | Build Context Management | HIGH | `ctx-` |
| 5 | Security & Secrets | HIGH | `sec-` |
| 6 | Dependency Management | MEDIUM-HIGH | `dep-` |
| 7 | Instruction Patterns | MEDIUM | `inst-` |
| 8 | Quality & Validation | MEDIUM | `lint-` |

## Quick Reference

### 1. Layer Caching & Ordering (CRITICAL)

- [`cache-layer-order`](references/cache-layer-order.md) - Order layers by change frequency
- [`cache-copy-deps-first`](references/cache-copy-deps-first.md) - Copy dependency files before source code
- [`cache-copy-link`](references/cache-copy-link.md) - Use COPY --link for cache-efficient layer copying
- [`cache-mount-package`](references/cache-mount-package.md) - Use cache mounts for package managers
- [`cache-apt-combine`](references/cache-apt-combine.md) - Combine apt-get update with install
- [`cache-external`](references/cache-external.md) - Use external cache for CI/CD builds
- [`cache-invalidation`](references/cache-invalidation.md) - Avoid unnecessary cache invalidation
- [`cache-minimize-layers`](references/cache-minimize-layers.md) - Consolidate related RUN instructions

### 2. Multi-Stage Builds (CRITICAL)

- [`stage-separate-build-runtime`](references/stage-separate-build-runtime.md) - Separate build and runtime stages
```
END THIRD-PARTY FILE 95e7b46e46a8bd67

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