tech.md

Container Technology

• Features of Linux (Kernel) used to implement containers
  • Process Isolation
    • Cgroups
    • Namespaces
  • UnionFS

Containers are a Linux (only) feature, made possible by those above. Non-Linux platforms (Windows, MacOS) require a Linux VM (behind the scenes) to run containers.

Terminology

• Container Runtime
  • Low-level component that executes containers and interfaces with kernel features
• Container Engine
  • Higher-level component that provides user-facing functionality, APIs, and commands
• Container Image:
  • Packaged, immutable template containing application code, libraries, and dependencies

• Tools that leverage or enhance features of containers

  • Image Manager (building etc)
    • docker, podman, buildah, kaniko
  • Container Runtime
    • docker, podman, container-d, cri-o
  • Container Orchestrator
    • kubernetes, openshift, rancher, nomad
  • Package Manager
    • helm
  • Development Platforms (for non-Linux systems)
    • Docker Desktop (MacOs and Windows)
      • bundles a Linux VM, Docker runtime, and UI
    • Podman Desktop (MacOs and Windows)
      • bundles a Linux VM, Podman runtime, and UI
    • Colima (MacOS)
      • bundles Linux VM (through Lima) with a container runtime Docker or Podman - configurable)
      • no GUI (command line only)
      • Docker/Podman Desktop do not use colima under the hood
      • Lima (MacOS)
        • provides a lightweight Linux VM; requires you to install a runtime like Docker or Podman separately