dockerfile-linter SKILL.md skillA
dockerfile-linter from lethe044/agentskill-kit is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
mdr add lethe044/agentskill-kit/dockerfile-linter@v1.0.0Pins v1.0.0 in mdr.lock. Pin the fingerprint instead.
- Audit grade
- A, 17 of 17 checks passed
- Kind
- SKILL.md skill
- Repository
- lethe044/agentskill-kit
- Path
skills/dockerfile-linter/SKILL.md- Versions recorded
- 1
- Latest version
- v1.0.0, committed Oct 26, 2026
- Size
- 1,868 bytes
- Repository stars
- 48
- License
- MIT
Checks a Dockerfile for common problems such as unpinned base images, running as root, ADD instead of COPY, secrets in ENV or ARG and apt-get without cleanup. Use when the user asks to review, harden or slim down a Dockerfile.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file says
# Dockerfile linter
A small rule set that catches the problems seen most often in real Dockerfiles, with line numbers.
## When to use
- The user asks for a review of a Dockerfile, or says an image is too big or insecure.
- Before a pull request that adds or changes a Dockerfile.
- When hardening a container that runs in production.
## How to run
```bash
python scripts/lint_dockerfile.py Dockerfile
```
## Rules
| Rule | Meaning |
| --- | --- |
| `DF001` | base image uses `latest` or has no tag, so builds are not reproducible |
| `DF002` | no `USER` instruction, the container runs as root |
| `DF003` | `ADD` used where `COPY` is enough (ADD is only needed for archives and URLs) |
| `DF004` | `apt-get install` without `--no-install-recommends` |
| `DF005` | `apt-get update` without removing `/var/lib/apt/lists` in the same layer |
| `DF006` | a secret-looking name (password, token, secret, api key) is set with `ENV` or `ARG` |
| `DF007` | `sudo` is used inside the image |
| `DF008` | no `HEALTHCHECK` (informational) |
## Output
JSON with `instructions` (count) and `findings`, a list of `{"line", "rule", "severity", "message"}`.
…Read the whole file at its exact version.
How to install
mdr add lethe044/agentskill-kit/dockerfile-linter@sha256:af1ef3564515b4aeThe line at the top of this page pins the label v1.0.0, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
[](https://markdownregistry.com/a/art_4yc5ykppco2dt3zd)
3 badge image fetches in 30 days. What the badge shows.
Versions
The registry has recorded 1 version of this file, committed on Oct 26, 2026.
Audit of the latest version
- pass: Frontmatter block present
- pass: Frontmatter declares a name
- pass: Frontmatter declares a description
- pass: Size between 200 bytes and 200 KB (1868 bytes)
- pass: No zero-width or bidi control characters
- pass: No instruction hidden inside an HTML comment
- pass: No link to an exfiltration or paste host
- pass: No credential-shaped string
- pass: No instruction to send local credentials anywhere
- pass: No text hidden with inline styles
- pass: No prompt-injection phrasing
- pass: No curl or wget piped into a shell
- pass: No recursive delete of root, home or parent
- pass: No instruction to read or print local credentials
- pass: No base64 blob over 200 characters
- pass: No link to a raw IP address
- pass: No script tag
Source
lethe044/agentskill-kit · 48 stars · license MIT · pushed 2026-10-26 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_4yc5ykppco2dt3zd GET https://markdownregistry.com/api/v1/resolve?ref=lethe044/agentskill-kit/dockerfile-linter GET https://markdownregistry.com/api/v1/blob/af1ef3564515b4ae9da126534830289059be88e2b8bf637097a61d55b403c21a
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
Guides: the SKILL.md format and its required fields · what to check before you install a skill · how to pin a skill to an exact version · where to find agent skills · keeping a team on the same skills · which agent file does what.