container-hardening

# Container Hardening

Secure container images and runtime configurations.

When to Use This Skill

Use this skill when:

- Building secure container images

- Hardening container deployments

- Meeting container security requirements

- Implementing defense in depth

Dockerfile Security

# Use minimal base image
FROM alpine:3.18

# Don't run as root
RUN addgroup -g 1001 -S appgroup && \
    adduser -u 1001 -S appuser -G appgroup

# Copy with specific ownership
COPY --chown=appuser:appgroup . /app

# Remove unnecessary packages
RUN apk del --purge build-dependencies && \
    rm -rf /var/cache/apk/*

# Use non-root user
USER appuser

# Read-only filesystem support
WORKDIR /app

Runtime Security

# Run with security options
docker run -d \
  --read-only \
  --tmpfs /tmp \
  --security-opt=no-new-privileges:true \
  --cap-drop=ALL \
  --cap-add=NET_BIND_SERVICE \
  --user 1001:1001 \
  myapp:latest

Kubernetes Security Context

apiVersion: v1
kind: Pod
spec:
  securityContext:
    runAsNonRoot: true
    runAsUser: 1001
    fsGroup: 1001
  containers:
  - name: app
    securityContext:
      allowPrivilegeEscalation: false
      readOnlyRootFilesystem: true
      capabilities:
        drop: ["ALL"]

Image Scanning

# Scan with Trivy
trivy image --severity HIGH,CRITICAL myapp:latest

# Use distroless images
FROM gcr.io/distroless/static-debian11

Best Practices

- Use minimal base images

- Run as non-root user

- Enable read-only filesystem

- Drop all capabilities

- Scan images regularly

- Sign and verify images

- Use secrets management

Related Skills

- container-scanning (`container-scanning`) - Vulnerability scanning

- kubernetes-hardening (`kubernetes-hardening`) - K8s security

Limitations

- Apply guidance only within authorized scope; test destructive steps in non-production first.

- Docs-only import: upstream scripts and templates not bundled.

Example

# Read-only first: inventory before any active step.
which <tool> && <tool> --help | head -n 20

> Adapted from [BagelHole/DevOps-Security-Agent-Skills](https://github.com/BagelHole/DevOps-Security-Agent-Skills) (MIT); frontmatter, When to Use/Limitations, and safety boundaries added for upstream compliance. Docs-only import: helper scripts and templates not bundled.