docker-image-hardening

docker-image-hardening is a skill for Claude Code, Codex from IkarusMK/AIcortex. It costs 32 tokens per session (304 once invoked), scanned A, original, Apache-2.0.

A checklist and set of practices for making Docker images smaller and safer. Docker images package an application and its dependencies so they can run consistently in containers.

In plain words
What is it for?
Use it when writing or reviewing Dockerfiles for deployed services. It covers pinned bases, multi-stage builds, non-root users, secret handling, health checks, and reducing image contents.
Why use it?
It reduces common risks such as running as an administrator, exposing secrets, shipping unnecessary software, or using an unverified base image.

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/ikarusmk/aicortex/docker-image-hardening
Any agent
npx skills add IkarusMK/AIcortex --skill docker-image-hardening
Clone the repo
git clone --depth 1 https://github.com/IkarusMK/AIcortex

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-image-hardening

README.md
[![agentmods](https://agentmods.dev/badge/skills/ikarusmk/aicortex/docker-image-hardening.svg)](https://agentmods.dev/skills/ikarusmk/aicortex/docker-image-hardening)
Your own site
<a href="https://agentmods.dev/skills/ikarusmk/aicortex/docker-image-hardening"><img src="https://agentmods.dev/badge/skills/ikarusmk/aicortex/docker-image-hardening.svg" alt="Measured on agentmods" height="20"></a>
Per session 32 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 304 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 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 $0.00032 $0.00304
Opus 5 $0.00016 $0.00152
Sonnet 5 $0.00006 $0.00061
Haiku 4.5 $0.00003 $0.00030

Measured 4d ago against content hash cf221a17f7b7, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

docker-image-hardening scanned grade A with 0 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 4d 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.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

examples/skills/docker-image-hardening/SKILL.md · 25 lines

What it actually says

Docker Image Hardening

When to use

Writing or reviewing a Dockerfile for anything that ships.

Checklist

  • Pin the base to a digest or specific tag, not latest. Prefer -slim / distroless.
  • Multi-stage build: compile in a builder stage, copy only artifacts into the final image.
  • Run as non-root: create a user, USER it; drop to it before CMD.
  • No secrets in layers: never COPY .env or bake tokens — pass at runtime / use a secret store. Layers are forever, even if a later layer deletes the file.
  • Minimize: --no-install-recommends, clean apt lists in the same RUN, .dockerignore the build context.
  • Healthcheck so the orchestrator knows when it's actually up.
  • Read-only where possible: mount data volumes explicitly; avoid writing into the image FS at runtime.

Smell tests

  • Image > a few hundred MB for a small service → something heavy leaked in.
  • docker history shows a secret or a huge dep layer → fix the Dockerfile, don't just squash.
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. 4d ago First seen · 25 lines · 32 tokens per session scan A cf221a17f7b7

Subscribe to this mod's changes

docker-image-hardening is a skill published in the GitHub repository IkarusMK/AIcortex (9 stars, last pushed 15d ago), licensed Apache-2.0. It adds 32 tokens to every session and 304 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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