docker

A guide to packaging a Yarn 4 monorepo, a repository containing several related projects, into Docker containers.

In plain words
What is it for?
Use it when writing Dockerfiles, setting up Docker Compose, reducing image size, adding health checks, or hardening containers.
Why use it?
It helps keep development and production containers small, cache builds effectively, run services safely, and avoid putting secrets in images.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/jgamaraalv/ts-dev-kit/docker
Any agent
npx skills add jgamaraalv/ts-dev-kit --skill docker
Clone the repo
git clone --depth 1 https://github.com/jgamaraalv/ts-dev-kit

Made for: Claude Code, Codex.

Per session 82 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 596 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00082 $0.00596
Opus 5 $0.00041 $0.00298
Sonnet 5 $0.00016 $0.00119
Haiku 4.5 $0.00008 $0.00060

Measured 2d ago against content hash 4d1347a34d74, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

docker scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Asks for rootlowPrivilege escalation

A mod that escalates privileges can change anything on the machine, not only the project.

- **Non-root users**: Create `app` user, never run as root in production

Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.

skills/docker/SKILL.md · 68 lines

How it starts

The opening of the file, as written. The whole thing — 68 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Docker — Containerization for Monorepos

Docker best practices for Node.js monorepos with Yarn 4 Berry.

Key Principles

  • Minimal images: Alpine-based, only runtime dependencies in final stage
  • Layer caching order: system deps → package manifests → install → source → build
  • Non-root users: Create app user, never run as root in production
  • One process per container: Compose multiple containers, not multiple processes
  • Health checks on every service: Use the existing /health endpoint

Image Optimization Quick Reference

  • Use node:22-alpine as base
  • Multi-stage builds: exclude build tools from final image
  • yarn cache clean after install
  • .dockerignore: exclude .git, node_modules, *.md, .env*, .claude, __tests__, coverage, .turbo
  • --production flag for runtime dependencies only
  • Pin base image versions (not just latest)

Container Security Quick Reference

  • Run as non-root user (addgroup --system app && adduser --system --ingroup app app)
  • Don't store secrets in images — use env vars or secrets management
  • Scan images: docker scout cves <image>
  • Set resource limits in compose: mem_limit, cpus
  • Read-only filesystem where possible: read_only: true
  • Drop capabilities: cap_drop: [ALL]

<quick_reference>

Useful Commands

docker compose build api          # Build specific service
docker compose up -d              # Start all services
docker compose logs -f api        # Follow logs
docker compose exec api sh        # Shell into container
docker images | grep myapp    # Check image sizes
docker system df                  # View cache usage
docker system prune -a            # Prune unused images
docker stats                      # Resource usage

</quick_reference>

When to Load References

Need Reference file
Writing or reviewing a Dockerfile for the monorepo references/monorepo-dockerfile.md
Configuring docker-compose for dev or production references/compose-configs.md

Read the full file on GitHub · 68 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 68 lines · 82 tokens per session scan A 4d1347a34d74

Subscribe to this mod's changes

docker is a skill published in the GitHub repository jgamaraalv/ts-dev-kit (15 stars, last pushed 6mo ago), licensed MIT. It adds 82 tokens to every session and 596 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 1 finding (asks for root). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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