Containers on a Linux System

D.

Containers are a form of lightweight virtualization that allows multiple isolated environments to run on a single Linux system. Containers use kernel-level functionalities such as cgroups and namespaces to create and manage isolated environments.

Option A is incorrect because while namespaces are necessary for containers, they are not the only required functionality. Cgroups are also essential for resource isolation and management.

Option B is incorrect because containers do not require a hypervisor to run on a Linux system. In fact, containers are often used as an alternative to traditional virtualization, which does require a hypervisor.

Option C is partially correct, as cgroups are indeed necessary for running containers. However, namespaces are also required for process isolation, network isolation, and filesystem isolation.

Option D is the correct answer. Containers use both cgroups and namespaces to isolate processes and allocate hardware resources to each isolated process. Cgroups provide resource management capabilities, such as limiting CPU, memory, and disk I/O usage, while namespaces provide process isolation, network isolation, and filesystem isolation.

In summary, containers running on a Linux system require both cgroups and namespaces functionalities to isolate processes, manage resources, and allocate hardware resources to each isolated process.