What Linux components are key for running Docker?

The key components of Linux necessary for Docker operation include:

• cgroups (control groups) — allow limiting and isolating resource usage (CPU, memory, disk, etc.) for containers.
• Namespaces — provide process, network interface, filesystem, and other resource isolation, creating separate namespace spaces for each container.
• UnionFS (e.g., OverlayFS) — a filesystem that allows creating image layers and managing them efficiently.
• Docker daemon (dockerd) — a service that interacts with the Linux kernel through the above mechanisms to manage containers.

Without support for cgroups and namespaces in the Linux kernel, Docker will not be able to isolate containers and manage resources.