Dockerfile Linter
Dockerfile Linter: Uses fixed line heuristics for FROM, image tags, USER, consecutive RUN, selected apt-get install, COPY, and ADD; it does not parse a Dockerfile AST or build images.
About this dockerfile linter
Dockerfile Linter — browser-based utility.
How this tool works
Uses fixed line heuristics for FROM, untagged or :latest images, USER, consecutive RUN, selected apt-get install, COPY, and ADD. It does not parse Dockerfile syntax, verify OCI compliance, or build images.
- Trim non-comment lines.
- Check FROM, image tag, USER, consecutive RUN, selected apt-get install, COPY, and ADD patterns.
- Return joined advisory warnings or the no-issue message.
Worked example
Scenario: Check a minimal pinned image with a non-root USER.
Sample input:
Processing: Scan lines for the limited advisory patterns.
Illustrative output:
Limits and verification
It does not parse an AST, continuation, stages, JSON instruction forms, variables, shell commands, manifests, BuildKit, vulnerabilities, or actual builds.
Examples demonstrate an expected workflow; they do not prove every input or every branch of an external specification. Check important results with an independent source before using them for money, security, compliance, safety, or irreversible file changes.
Browser processing boundary
Tool input is processed by code running in the browser and is not intentionally sent to a CZOA processing API. The page can still request ordinary site assets, analytics, or advertising when those services are enabled. Browser extensions and managed-device software remain outside this tool's control.
Relevant references
These references govern or help explain the format, protocol, or calculation used here. Listing a reference does not claim certification or complete implementation of every optional feature.
- Standard Browser Web API / Algorithm Implementation (No single external RFC/ISO standard)
Content owner: CZOA Tools · Last reviewed: 2026-09-15 · Review methodology
How to use it
- Enter, paste, or select your input data into the Dockerfile Linter workspace controls.
- Review available parameter fields, units, formats, or options configured for your task.
- Click the action button or observe immediate live calculations rendered in your browser runtime.
- Inspect the resulting output and any diagnostic messages, then copy or download the result if needed.
Frequently asked questions
What does Dockerfile Linter actually check?+
It uses line heuristics for a FROM instruction, untagged or `:latest` images, missing or root USER, consecutive RUN lines, selected apt-get install usage, and COPY or ADD with fewer than two arguments.
What result does a minimal Dockerfile produce?+
`FROM node:20` plus `USER app` returns `No basic Dockerfile issues detected.` It means this checker’s listed line patterns did not match; it does not establish that an image is secure, buildable, or production-ready.
What Dockerfile syntax is not parsed?+
The tool does not build an AST or understand continuations, stages, JSON instruction forms, variables, shell command behavior, image manifests, BuildKit, vulnerabilities, or actual Docker build results.
Does the page build or upload a Dockerfile?+
No. The browser test processes entered Dockerfile text and finds no tool request carrying it. The page does not start Docker, pull images, or inspect a daemon; ordinary page resources are separate.