Containers

• What is a Container?

  • Lightweight and portable.
  • OS-level virtualization (compared to VMs).
  • Runs applications and dependencies in an isolated environment.

• Container Runtime:

  • OCI standards for container image format.
  • Examples: containerd, CRI-O, runc, Docker.
  • How Kubernetes interacts with container runtimes through the Container Runtime Interface (CRI).

• Container Images:

  • Layers and image composition.
  • Building images using Dockerfile.
  • Storing and retrieving images from registries (Docker Hub, Artifact Registry, etc.).

• Container Lifecycle:

  • Creation, running, stopping containers.
  • Restart policies in Kubernetes (Always, OnFailure, Never).

• Security:

  • Image scanning and vulnerability management.
  • Running containers with least privilege (user ID and group).
  • Container isolation using namespaces and cgroups.

• Networking:

  • Container Network Interface (CNI) plugins.
  • Port mapping and exposing services.
  • Container-to-container and container-to-host communication.

• Storage:

  • Ephemeral storage (temporary storage for containers).
  • Persistent storage (using volumes in Kubernetes).
  • Mounting and sharing volumes between containers.