What do OS containers utilize to ensure isolated user space?

OS containers utilize the shared kernel of the host environment to ensure isolated user space. This approach allows multiple containers to run on a single host operating system while maintaining their own isolated environments. Each container operates with its own user space, meaning that the applications running inside a container feel as if they are executing in their own dedicated environment. However, they all share the same underlying kernel of the host OS.

This shared kernel model is efficient because it minimizes the overhead associated with running separate operating systems for each application, as is seen in full virtualization. Instead of requiring dedicated hardware resources or separate physical servers for each user space, containers leverage the host's kernel to manage processes, memory, and system calls, making deployment and resource management faster and more efficient. The containerization technology thus allows for greater density and scalability of applications on a single physical server, which is a key advantage in modern application development and deployment scenarios.