Dockerfile Linter

Checking Dockerfiles for Common Issues Before Building Images

Dockerfiles are used to define how container images are built. Small mistakes in a Dockerfile can create larger images, slower builds, missing runtime files, security risks, or deployment problems later.

This Dockerfile Linter helps you check Dockerfile content for common issues such as missing base images, risky root usage, unpinned base images, unnecessary cache files, exposed secrets, and basic Docker best practice problems directly in your browser.

Reviewing Dockerfile Syntax and Build Instructions

1. Paste your Dockerfile content into the input box.
2. Click Check Dockerfile.
3. Review the warnings and suggestions in the output.
4. Update your Dockerfile before building or deploying the image.

Common Dockerfile Lint Checks

• Checking whether a Dockerfile has a FROM instruction.
• Finding unpinned base images such as latest.
• Reviewing risky package installation patterns.
• Checking whether a non-root user is configured.
• Finding possible secret values copied into the image.
• Reviewing common Dockerfile best practice suggestions.

Example Dockerfile to Check

FROM node:20-alpine

WORKDIR /app

COPY package*.json ./
RUN npm install

COPY . .

EXPOSE 3000

CMD ["npm", "start"]

Frequently Asked Questions

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