2.6. Virtualization on Linux

Virtualization lets you run multiple isolated operating systems on a single physical host. In a cloud world, understanding virtualization is prerequisite knowledge — every cloud VM is a virtual machine running on a hypervisor. For the XK0-006 exam, virtualization appears both as a standalone topic and as foundational context for container management (Phase 3) and cloud automation (Phase 5).

💡 First Principle: A hypervisor intercepts hardware access from guest operating systems and multiplexes it across the physical hardware. The guest OS believes it has real hardware; the hypervisor translates those beliefs into actual resource allocations. This indirection is what makes VM isolation, snapshots, and migration possible.

⚠️ Common Misconception (M4): VMs and containers are often conflated, but they differ fundamentally. A VM runs a complete OS kernel on virtualized hardware — strong isolation, higher overhead. A container shares the host kernel and uses namespace/cgroup isolation — faster, lower overhead, weaker isolation. This distinction matters for security and performance decisions on the exam.

Virtualization underpins cloud infrastructure. Without understanding hypervisors, CPU virtualization extensions, and the guest/host boundary, you cannot diagnose VM performance issues, configure nested virtualisation, or understand why a VM behaves differently from a bare-metal host with identical specs.