How is container isolation implemented in Docker?

Container isolation in Docker is achieved through the use of Linux kernel features such as:

• Namespaces — create isolated spaces for processes, network interfaces, filesystems, and other resources. This allows containers to have their own processes, network, and filesystem without affecting the host or other containers.

• Control Groups (cgroups) — limit and control resource usage (CPU, memory, disk) by containers, preventing impact on host performance and other containers.

• Union File Systems (e.g., OverlayFS) — provide layered filesystems, allowing a container to have its own isolated filesystem layer on top of a base image.

Together, these mechanisms ensure that containers operate in an isolated environment with limited resources and their own namespace, ensuring security and predictability of applications inside containers.