Docker Security Best Practices

Containers share the host kernel, so a misconfigured container can expose the entire host. This lesson covers the essential security practices every Docker user should follow — from running as non-root and using minimal base images, to scanning for vulnerabilities, managing secrets, and applying resource limits.

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The Security Mindset

Container security operates at multiple layers:

+-----------------------------------------------+
|  1. Image Security                             |
|     - Minimal base images                      |
|     - No secrets in images                     |
|     - Vulnerability scanning                   |
+-----------------------------------------------+
|  2. Build Security                             |
|     - Trusted base images                      |
|     - .dockerignore                            |
|     - Multi-stage builds                       |
+-----------------------------------------------+
|  3. Runtime Security                           |
|     - Non-root user                            |
|     - Read-only filesystem                     |
|     - Resource limits                          |
|     - Dropped capabilities                     |
+-----------------------------------------------+
|  4. Network Security                           |
|     - Network isolation                        |
|     - Least-privilege port exposure            |
+-----------------------------------------------+
|  5. Secrets Management                         |
|     - Never bake secrets into images           |
|     - Use environment variables or secret mgmt |
+-----------------------------------------------+

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Running as Non-Root

By default, containers run as root — this is the single most common Docker security mistake.