/configure:dockerfile

Check and configure Dockerfile against project standards with emphasis on minimal images, non-root users, and multi-stage builds.

When to Use This Skill

Use this skill when...	Use another approach when...
Checking Dockerfile compliance with standards	Just viewing Dockerfile (use Read tool)
Creating Dockerfile from template	Dockerfile already follows all standards
Validating image size, security, multi-stage builds	Need container runtime config (use /configure:container)
Setting up minimal Alpine/slim-based images	Project uses specialized base images (custom requirements)
Ensuring non-root user configuration	Debugging container issues (check logs, inspect runtime)

Context

• Dockerfiles: !find . -maxdepth 1 \( -name 'Dockerfile' -o -name 'Dockerfile.*' -o -name '*.Dockerfile' \)
• Dockerignore: !find . -maxdepth 1 -name \'.dockerignore\'
• Project type: !find . -maxdepth 1 \( -name 'package.json' -o -name 'pyproject.toml' -o -name 'Cargo.toml' -o -name 'go.mod' \) -print -quit
• Base images: !grep -hm5 '^FROM' Dockerfile Dockerfile.* *.Dockerfile

Parameters

Parse from command arguments:

• --check-only: Report compliance status without modifications
• --fix: Apply fixes automatically without prompting
• --type <type>: Override project type detection (frontend, python, go, rust)

Execution

Execute this Dockerfile compliance check:

Step 1: Detect project type and Dockerfiles

1. Find Dockerfile(s) in project root
2. Detect project type from context (package.json, pyproject.toml, go.mod, Cargo.toml)
3. Parse Dockerfile to analyze current configuration
4. Apply --type override if provided

Step 2: Verify latest base image versions

Before flagging outdated base images, use WebSearch or WebFetch to verify latest versions:

1. Node.js Alpine: Check Docker Hub for latest LTS Alpine tags
2. Python slim: Check Docker Hub for latest slim tags
3. nginx Alpine: Check Docker Hub for latest Alpine tags
4. Go Alpine: Check Docker Hub for latest Alpine tags
5. Rust Alpine: Check Docker Hub for latest Alpine tags

Step 3: Analyze compliance

Check the Dockerfile against these standards:

Frontend (Node.js) Standards:

Check	Standard	Severity
Build base	node:22-alpine (LTS)	WARN if other
Runtime base	nginx:1.27-alpine	WARN if other
Multi-stage	Required	FAIL if missing
HEALTHCHECK	Required	FAIL if missing
Non-root user	Required	FAIL if missing
Build caching	--mount=type=cache recommended	INFO
OCI Labels	Required for GHCR integration	WARN if missing

Python Service Standards:

Check	Standard	Severity
Base image	python:3.12-slim	WARN if other
Multi-stage	Required for production	FAIL if missing
HEALTHCHECK	Required	FAIL if missing
Non-root user	Required	FAIL if missing
OCI Labels	Required for GHCR integration	WARN if missing

OCI Container Labels:

Label	Purpose	Severity
org.opencontainers.image.source	Links to repository	WARN if missing
org.opencontainers.image.description	Package description	WARN if missing
org.opencontainers.image.licenses	SPDX license identifier	WARN if missing
org.opencontainers.image.version	Semantic version (via ARG)	INFO if missing
org.opencontainers.image.revision	Git commit SHA (via ARG)	INFO if missing

Step 4: Report results

Print a compliance report:

Dockerfile Compliance Report
================================
Project Type: <type> (detected)
Dockerfile: ./Dockerfile (found)

Configuration Checks:
  Build base      <image>           [PASS|WARN]
  Runtime base    <image>           [PASS|WARN]
  Multi-stage     <N> stages        [PASS|FAIL]
  HEALTHCHECK     <present|missing> [PASS|FAIL]
  Non-root user   <present|missing> [PASS|FAIL]
  Build caching   <enabled|missing> [PASS|INFO]

OCI Labels Checks:
  image.source       <present|missing> [PASS|WARN]
  image.description  <present|missing> [PASS|WARN]
  image.licenses     <present|missing> [PASS|WARN]

Recommendations:
  <list specific fixes needed>

If --check-only, stop here.

Step 5: Apply fixes (if requested)

If --fix flag is set or user confirms:

1. Missing Dockerfile: Create from standard template (see Standard Templates below)
2. Missing HEALTHCHECK: Add standard healthcheck
3. Missing multi-stage: Suggest restructure (manual fix needed)
4. Outdated base images: Update FROM lines
5. Missing OCI labels: Add LABEL instructions

Step 6: Update standards tracking

Update .project-standards.yaml:

components:
  dockerfile: "2025.1"

Standard Templates

Frontend (Node/Vite/nginx)

FROM node:22-alpine AS build

ARG SENTRY_AUTH_TOKEN
ARG VITE_SENTRY_DSN

WORKDIR /app

COPY package*.json ./
RUN --mount=type=cache,target=/root/.npm npm ci

COPY . .
RUN --mount=type=cache,target=/root/.npm \
    --mount=type=cache,target=/app/node_modules/.vite \
    npm run build

FROM nginx:1.27-alpine

# OCI labels for GHCR integration
LABEL org.opencontainers.image.source="https://github.com/OWNER/REPO" \
      org.opencontainers.image.description="Production frontend application" \
      org.opencontainers.image.licenses="MIT" \
      org.opencontainers.image.vendor="Your Organization"

# Dynamic labels via build args
ARG VERSION=dev
ARG BUILD_DATE
ARG VCS_REF
LABEL org.opencontainers.image.version="${VERSION}" \
      org.opencontainers.image.created="${BUILD_DATE}" \
      org.opencontainers.image.revision="${VCS_REF}"

COPY --from=build /app/dist /usr/share/nginx/html
COPY nginx/default.conf.template /etc/nginx/templates/

EXPOSE 80

HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
  CMD wget --no-verbose --tries=1 --spider http://localhost/health || exit 1

Python Service

FROM python:3.12-slim AS builder

WORKDIR /app
COPY pyproject.toml uv.lock ./
RUN pip install uv && uv sync --frozen --no-dev

FROM python:3.12-slim

# OCI labels for GHCR integration
LABEL org.opencontainers.image.source="https://github.com/OWNER/REPO" \
      org.opencontainers.image.description="Production Python API server" \
      org.opencontainers.image.licenses="MIT" \
      org.opencontainers.image.vendor="Your Organization"

ARG VERSION=dev
ARG BUILD_DATE
ARG VCS_REF
LABEL org.opencontainers.image.version="${VERSION}" \
      org.opencontainers.image.created="${BUILD_DATE}" \
      org.opencontainers.image.revision="${VCS_REF}"

RUN useradd --create-home appuser
USER appuser
WORKDIR /app

COPY --from=builder /app/.venv /app/.venv
COPY --chown=appuser:appuser . .

ENV PATH="/app/.venv/bin:$PATH"
EXPOSE 8000

HEALTHCHECK --interval=30s --timeout=3s --start-period=10s --retries=3 \
  CMD curl -f http://localhost:8000/health || exit 1

CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]

Agentic Optimizations

Context	Command
Check Dockerfile exists	find . -maxdepth 1 \( -name 'Dockerfile' -o -name 'Dockerfile.*' \) 2>/dev/null
Validate multi-stage build	grep -c '^FROM' Dockerfile 2>/dev/null
Check for non-root user	grep -E '^USER [^root]' Dockerfile 2>/dev/null
Check base image	grep '^FROM' Dockerfile | head -1
Quick compliance check	/configure:dockerfile --check-only
Auto-fix issues	/configure:dockerfile --fix

Flags

Flag	Description
--check-only	Report status without offering fixes
--fix	Apply fixes automatically
--type <type>	Override project type (frontend, python)

Notes

• Node 22 is current LTS (recommended over 24)
• nginx:1.27-alpine preferred over debian variant
• HEALTHCHECK is critical for Kubernetes liveness probes
• Build caching significantly improves CI/CD speed
• Non-root user is mandatory for production containers

See Also

• /configure:container - Comprehensive container infrastructure
• /configure:skaffold - Kubernetes development configuration
• /configure:all - Run all compliance checks
• container-development skill - Container best practices