docker

docker is a skill for Claude Code, Codex from ericrisco/rsc-harness. It costs 86 tokens per session (3,088 once invoked), scanned B, original, MIT.

A guide to building and running Docker containers: packaged application environments that include the code and its dependencies. It focuses on Dockerfiles, image size, security, build caching, and local Compose setups.

In plain words
What is it for?
Use it to write or review Dockerfiles, choose base images, create .dockerignore files, harden containers, and set up a hot-reloading multi-service development stack.
Why use it?
It helps remove oversized images, slow builds, unsafe root containers, and awkward local development setups. It also keeps image creation separate from deployment and CI work.

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/ericrisco/rsc-harness/docker
Any agent
npx skills add ericrisco/rsc-harness --skill docker
Clone the repo
git clone --depth 1 https://github.com/ericrisco/rsc-harness

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for docker

README.md
[![agentmods](https://agentmods.dev/badge/skills/ericrisco/rsc-harness/docker.svg)](https://agentmods.dev/skills/ericrisco/rsc-harness/docker)
Your own site
<a href="https://agentmods.dev/skills/ericrisco/rsc-harness/docker"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/docker.svg" alt="Measured on agentmods" height="20"></a>
Per session 86 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,088 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. 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 $0.00086 $0.03088
Opus 5 $0.00043 $0.01544
Sonnet 5 $0.00017 $0.00618
Haiku 4.5 $0.00009 $0.00309

Measured yesterday against content hash 2fddcbec69b6, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

docker scanned grade B with 2 findings 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 yesterday.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/verify.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

Recursive force deletemediumDestructive command

rm -rf with a variable or a broad path is one typo away from removing the wrong tree.

| `apt-get install x` | `apt-get install --no-install-recommends x && rm -rf /var/lib/apt/lists/*` | recommends + apt lists bloat the layer |

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

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

HEALTHCHECK CMD ["python", "-c", "import urllib.request,sys; sys.exit(0 if urllib.request.urlopen('http://localhost:8000/health').status==200 else 1)"]
skills/docker/SKILL.md · 252 lines

How it starts

The opening of the file, as written. The whole thing — 252 lines — stays where its author put it; the contents beside it link to each section on GitHub.

docker — container-craft

You own one question, deeply: how do I turn this app into a small, secure, fast-building image — and run a frictionless local stack with Compose? Your artifacts are the Dockerfile, the .dockerignore, and the compose.yaml: their layers, their attack surface, their build cache, their dev loop. You do not touch what happens after the image is built.

source  →  Dockerfile (multi-stage, cache mounts)  →  small + scanned image  +  compose.yaml (dev loop)
                                                            └──────────────┬──────────────┘
                                                    hand off to ../deployment/SKILL.md

The hand-off is sharp: the moment you have a green, scanned image and a working compose.yaml, you are done. Everything downstream is ../deployment/SKILL.md — it already references Dockerfiles and leans on you for the image internals.

When NOT to use — and who owns it instead

You're asked for… Owner Why it's not you
CI build, registry push, deploy to host, rollback ../deployment/SKILL.md You build + harden the image; it moves the image through CI to prod
k8s manifests, HPA autoscaling, ingress scaling Orchestration above a single image
App SQL injection, secrets in source, dep CVE triage ../secure-coding/SKILL.md You cover only image/container hardening
Install/operate a self-hosted PaaS ../coolify/SKILL.md Host operation, not the image
Containerless PaaS deploy mechanics ../railway/SKILL.md, ../fly-io/SKILL.md Platform deploy, not the Dockerfile

Pick a base image (2026 reality)

Base Size CVE / patch velocity Debuggable? Wins when
*-slim (e.g. bookworm-slim) ~30–80 MB moderate, glibc yes (shell, apt) pragmatic default, native deps / Python wheels
distroless (gcr.io/distroless/*) ~2–25 MB convenient but patches slower no shell static/compiled runtimes, want minimal surface
Chainguard / Wolfi tiny, glibc lowest live CVE count, SLSA L3 attestations minimal security-first; real scans found high-sev CVEs where the Chainguard equivalent had zero
alpine ~5 MB, musl small surface yes (apk) tiny static services — but musl breaks many Python wheels / native deps
scratch 0 nothing to patch no a fully static binary (Go), nothing else

Read the full file on GitHub · 252 lines

Files

What ships with it

5 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. yesterday First seen · 252 lines · 86 tokens per session scan B 2fddcbec69b6

Subscribe to this mod's changes

docker is a skill published in the GitHub repository ericrisco/rsc-harness (64 stars, last pushed 2d ago), licensed MIT. It adds 86 tokens to every session and 3,088 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it B with 2 findings (recursive force delete, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

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