# Container Hardening

> Secure Docker images and container runtime configurations. Implement non-root users, read-only filesystems, and security contexts. Use when building secure container images or hardening container deployments.

- Skill: `majiayu000/container-hardening` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds add majiayu000/container-hardening`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/container-hardening/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: DevOps & Infra
- License: MIT
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/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

```dockerfile
# 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

```bash
# 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

```yaml
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

```bash
# 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](../../scanning/container-scanning/) - Vulnerability scanning
- [kubernetes-hardening](../kubernetes-hardening/) - K8s security