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docker-agents-review

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SKILL.md

docker-agents-review

Review Workflow

Execute these checklists in order. Each section is independent -- report all findings, do not stop at the first issue.

Review Order:
1. Dockerfile Validation     --> Base image, instructions, layers, signals
2. Compose Validation        --> Structure, depends_on, volumes, env
3. Security Audit            --> Non-root, capabilities, secrets, scanning
4. Production Readiness      --> Health checks, restart, logging, limits
5. Anti-Pattern Scan         --> Known mistakes across all areas

Checklist 1: Dockerfile Validation

1A: Base Image

[ ] Base image uses a specific version tag (NEVER `latest`)
    FAIL: FROM node:latest | FROM nginx
    PASS: FROM node:20.11-bookworm-slim
[ ] Production stage uses minimal base (alpine, slim, distroless, or scratch)
    FAIL: Full OS image in final stage (ubuntu:22.04, debian:bookworm)
[ ] Multi-stage build separates build dependencies from runtime
    FAIL: Compiler/SDK present in final image
[ ] Build stage named with AS keyword
    FAIL: COPY --from=0 (fragile numeric index)
    PASS: FROM golang:1.22 AS build ... COPY --from=build
[ ] For reproducible builds, digest pinning used where required
    BEST: FROM alpine:3.21@sha256:abc123...

1B: Instructions & Layer Optimization

[ ] syntax directive present at top of Dockerfile
    EXPECTED: # syntax=docker/dockerfile:1
[ ] COPY used instead of ADD for local files
    FAIL: ADD config.json /app/ (when no extraction needed)
[ ] apt-get update && install combined in single RUN
    FAIL: Separate RUN apt-get update and RUN apt-get install
[ ] apt cache cleaned after install
    EXPECTED: && rm -rf /var/lib/apt/lists/*
[ ] --no-install-recommends used with apt-get install
[ ] Package versions pinned where determinism required
[ ] Related commands combined with && to minimize layers
    FAIL: Separate RUN for each apt-get install package
[ ] WORKDIR used instead of RUN cd
    FAIL: RUN cd /app && npm install
[ ] .dockerignore file exists and excludes node_modules, .git, build artifacts
[ ] COPY instruction ordered for cache efficiency
    EXPECTED: COPY package*.json first, then RUN npm install, then COPY . .

1C: Entrypoint & Signals

[ ] ENTRYPOINT uses exec form (JSON array)
    FAIL: ENTRYPOINT /usr/bin/myapp (shell form)
    PASS: ENTRYPOINT ["/usr/bin/myapp"]
[ ] CMD uses exec form (JSON array)
    FAIL: CMD node server.js
    PASS: CMD ["node", "server.js"]
[ ] Entrypoint scripts use exec "$@" to replace shell process
[ ] Application runs as PID 1 for proper signal handling
[ ] Shell form NOT used for ENTRYPOINT (prevents SIGTERM delivery)
[ ] Pipe commands use set -o pipefail
    FAIL: RUN wget -O - https://url | wc -l > /count
    PASS: RUN set -o pipefail && wget -O - https://url | wc -l > /count

1D: Metadata & Documentation

[ ] EXPOSE documents all listening ports
[ ] OCI standard labels present (org.opencontainers.image.*)
[ ] HEALTHCHECK defined in Dockerfile
[ ] No deprecated MAINTAINER instruction (use LABEL instead)

Checklist 2: Compose Validation

2A: File Structure

[ ] No `version:` field (deprecated and ignored by modern Compose)
    FAIL: version: "3.8"
[ ] File named compose.yaml (preferred) or docker-compose.yml
[ ] Services use specific image tags (NEVER latest)
[ ] Project name defined via `name:` field or CLI flag

2B: Service Dependencies

[ ] depends_on uses condition: service_healthy (not bare dependency)
    FAIL: depends_on: [db] (only waits for start, not ready)
    PASS: depends_on: { db: { condition: service_healthy } }
[ ] Services with depends_on: service_healthy have healthcheck defined
    FAIL: condition: service_healthy without healthcheck on target
[ ] Database services have appropriate healthcheck
    EXAMPLE: test: ["CMD-SHELL", "pg_isready -U postgres"]

2C: Volumes & Storage

[ ] Named volumes used for persistent data (NEVER anonymous)
    FAIL: volumes: [/var/lib/postgresql/data]
    PASS: volumes: [db-data:/var/lib/postgresql/data]
[ ] Named volumes declared in top-level volumes: section
[ ] Bind mounts use absolute paths or named volumes
[ ] Database data directories use named volumes

2D: Environment & Secrets

[ ] Secrets NOT hardcoded in environment values
    FAIL: DATABASE_PASSWORD: "my-secret"
    PASS: DATABASE_PASSWORD: ${DATABASE_PASSWORD:?Required}
[ ] env_file used for environment-specific configuration
[ ] Sensitive values use Compose secrets (not environment)
[ ] Variable interpolation uses error syntax for required vars
    EXPECTED: ${VAR:?Error message}

2E: Networking & Ports

[ ] Development ports bound to localhost
    FAIL: ports: ["8080:80"]
    PASS: ports: ["127.0.0.1:8080:80"]
[ ] Services that do not need external access use expose (not ports)
[ ] Network isolation implemented where services should not communicate
    EXAMPLE: frontend/backend network separation
[ ] container_name NOT used on scalable services
    FAIL: container_name: my-nginx (prevents scaling)

2F: Resource Management

[ ] Resource limits defined (deploy.resources.limits)
    EXPECTED: cpus and memory limits set
[ ] restart policy appropriate (unless-stopped or on-failure, NOT always without limits)
    FAIL: restart: always without deploy.resources.limits
[ ] Optional/debug services use profiles
    FAIL: phpmyadmin always running in production
    PASS: phpmyadmin with profiles: [debug]

Checklist 3: Security Audit

3A: Container User

[ ] Dockerfile creates and switches to non-root USER
    FAIL: No USER instruction (runs as root)
    PASS: RUN groupadd -r app && useradd -r -g app app ... USER app
[ ] USER instruction uses explicit UID/GID for determinism
[ ] --no-log-init flag used with useradd
[ ] gosu used instead of sudo in entrypoint scripts

3B: Capabilities & Privileges

[ ] --privileged NOT used in production
    FAIL: privileged: true in compose.yaml
[ ] Capabilities dropped and only needed ones added
    BEST: cap_drop: [ALL] + cap_add: [NET_BIND_SERVICE]
[ ] no-new-privileges security option set
    EXPECTED: security_opt: [no-new-privileges:true]
[ ] Read-only root filesystem where possible
    EXPECTED: read_only: true with tmpfs for /tmp, /run

3C: Secrets & Sensitive Data

[ ] No secrets in ENV or ARG instructions
    FAIL: ENV API_KEY=sk-123 or ARG DATABASE_PASSWORD=secret
[ ] Build secrets use --mount=type=secret
    PASS: RUN --mount=type=secret,id=token cat /run/secrets/token
[ ] No secrets committed to .dockerignore-excluded files
[ ] No sensitive data in docker history (check with docker history)

3D: Image Security

[ ] Images scanned for vulnerabilities (docker scout cves)
[ ] Base images from official/trusted sources
[ ] No unnecessary packages installed in final image
[ ] Build tools NOT present in production image (use multi-stage)

3E: Network Security

[ ] Internal services NOT exposed to host network
[ ] Ports bound to specific interfaces where possible
[ ] Network isolation between frontend and backend tiers
[ ] No host network mode without justification

Checklist 4: Production Readiness

4A: Health Checks

[ ] HEALTHCHECK defined in Dockerfile or Compose healthcheck
[ ] Health check interval, timeout, retries configured
    EXPECTED: interval=30s, timeout=5s, start_period=10s, retries=3
[ ] Health check command tests actual service readiness
    FAIL: CMD true (always passes)
    PASS: CMD curl -f http://localhost/health || exit 1
[ ] start_period allows for application startup time

4B: Restart & Recovery

[ ] Restart policy set (unless-stopped or on-failure)
[ ] on-failure has max_attempts limit to prevent crash loops
[ ] Resource limits prevent runaway container resource consumption
[ ] Logging configured with size rotation
    EXPECTED: logging driver with max-size and max-file options

4C: Observability

[ ] Structured logging to stdout/stderr (NOT to files inside container)
[ ] Log rotation configured (max-size, max-file)
    FAIL: No log rotation (fills disk)
    PASS: logging: { options: { max-size: "10m", max-file: "3" } }
[ ] Container metrics accessible via docker stats
[ ] Health status queryable via docker inspect

4D: Build Reproducibility

[ ] Base images pinned to specific version (or digest)
[ ] Package versions pinned where critical
[ ] Build cache strategy defined (cache-from, cache-to)
[ ] .dockerignore prevents build context bloat
[ ] Multi-platform build configured if needed

Checklist 5: Anti-Pattern Scan

Scan the codebase for these known issues. See references/anti-patterns.md for full details.

Dockerfile Anti-Patterns

[ ] No FROM with latest tag
[ ] No shell form ENTRYPOINT
[ ] No separate apt-get update and install
[ ] No missing apt cache cleanup
[ ] No ADD when COPY suffices
[ ] No RUN cd instead of WORKDIR
[ ] No secrets in ENV or ARG
[ ] No ENV persistence leak (unset in same RUN)
[ ] No missing .dockerignore
[ ] No running as root without justification
[ ] No too-many-layers (combine related RUN)
[ ] No missing syntax directive

Compose Anti-Patterns

[ ] No version: field present
[ ] No depends_on without healthcheck condition
[ ] No anonymous volumes for persistent data
[ ] No hardcoded secrets in environment
[ ] No container_name on scalable services
[ ] No restart: always without resource limits
[ ] No ports exposed to all interfaces (0.0.0.0)
[ ] No debug services without profiles

Security Anti-Patterns

[ ] No --privileged in production
[ ] No running as root without USER instruction
[ ] No host network without justification
[ ] No missing capability drops
[ ] No secrets baked into image layers

Decision Trees

Is the Dockerfile production-ready?

Does it use multi-stage build?
+-- No --> Add build + runtime stages
+-- Yes
    |
    Does the final stage use a minimal base?
    +-- No --> Switch to alpine/slim/distroless
    +-- Yes
        |
        Does it run as non-root?
        +-- No --> CRITICAL: Add USER instruction
        +-- Yes
            |
            Does it have a HEALTHCHECK?
            +-- No --> Add health check
            +-- Yes
                |
                Does it use exec form for ENTRYPOINT/CMD?
                +-- No --> Convert to JSON array format
                +-- Yes --> PASS

Is the Compose file production-ready?

Does it have a version: field?
+-- Yes --> Remove it (deprecated)
+-- No
    |
    Do all depends_on use service_healthy?
    +-- No --> Add healthchecks and conditions
    +-- Yes
        |
        Are all persistent volumes named?
        +-- No --> CRITICAL: Replace anonymous volumes
        +-- Yes
            |
            Are resource limits set?
            +-- No --> Add deploy.resources.limits
            +-- Yes
                |
                Are secrets properly managed?
                +-- No --> Move to Compose secrets or env_file
                +-- Yes --> PASS

Review Report Template

After completing all checklists, produce a report:

## Docker Configuration Review Report

### Summary
- Total issues found: X
- Critical (blocks deployment): X
- Warning (should fix): X
- Info (improvement suggestion): X

### Critical Issues
1. [CRIT-001] Description -- Location -- Fix

### Warnings
1. [WARN-001] Description -- Location -- Fix

### Passed Checks
- Dockerfile Validation: PASS/FAIL (X/Y checks passed)
- Compose Validation: PASS/FAIL
- Security Audit: PASS/FAIL
- Production Readiness: PASS/FAIL
- Anti-Pattern Scan: PASS/FAIL

Reference Links

Official Sources

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