Which open source technology is used for developing, packaging and running applications in containers and provides OS-level virtualization?

• A. Docker
• B. Kubernetes
• C. VirtualBox
• D. VMware

Answer: (A)

Containers rely on OS-level virtualization, which means applications run in isolated user-space environments that share the host's kernel, making them lightweight and portable. The open source tool designed to develop, package, and run these containers is Docker. Docker provides the runtime, image format, and tooling you use to build an image with your application and its dependencies, then run it consistently on any host with Docker. Kubernetes, while essential for managing many containers across multiple hosts, is an orchestration system, not the container runtime itself. VirtualBox and VMware are traditional full virtualization platforms that run separate guest operating systems on virtual hardware, not OS-level containers.