KVM
also: Kernel-based Virtual Machine
KVM (Kernel-based Virtual Machine) is a Linux kernel module that enables hardware virtualization, allowing a single physical machine to run multiple isolated virtual machines efficiently.
KVM is a virtualization technology built directly into the Linux kernel since version 2.6.20. It leverages CPU virtualization extensions (Intel VT-x or AMD-V) to create and manage virtual machines without emulating hardware, making it fast and efficient for production workloads.
When KVM is loaded as a kernel module, the system becomes a hypervisor capable of running unmodified guest operating systems. Each virtual machine runs as a regular Linux process but with isolated CPU, memory, and I/O resources.
Example: Running KVM alongside QEMU, you could launch a virtual Ubuntu instance with: qemu-system-x86_64 -enable-kvm -m 2G ubuntu.qcow2. The -enable-kvm flag instructs QEMU to use KVM acceleration rather than pure software emulation, resulting in near-native performance.
KVM is free, open-source, and widely used in cloud platforms (OpenStack, AWS, Google Cloud) and enterprise virtualization because it offers strong performance, security isolation, and requires minimal overhead compared to other hypervisors.