Docker Internal Implementation

Question: Explain how Docker works internally — what mechanisms does it use to provide container isolation?

Answer outline: Docker containers are built on Linux kernel primitives: namespaces (PID, network, mount, UTS, IPC, user) provide process/resource isolation so each container sees its own isolated view of the system, and cgroups (control groups) enforce resource limits (CPU, memory, I/O) per container. Images are layered filesystems (using a union filesystem like overlay2) where each Dockerfile instruction adds a read-only layer, and a thin writable layer is added at container runtime.