libvirt Virtualization API

libvirt is an open-source API, daemon, and management tool for managing platform virtualization. Originally developed by Daniel Veillard at Red Hat in 2005, libvirt provides a unified API for managing various virtualization technologies including KVM, QEMU, Xen, LXC, OpenVZ, VirtualBox, VMware ESX, and Microsoft Hyper-V. Key features: unified C API for managing virtual machines, storage, networking, and snapshots across multiple hypervisors, abstracting away hypervisor-specific details. Driver architecture with separate drivers for each hypervisor (QEMU/KVM, Xen, LXC, VirtualBox, VMware, Hyper-V, Bhyve, Test), enabling the same management code to work across different platforms. Domain (virtual machine) lifecycle management including create, start, pause, resume, stop, destroy, reboot, migrate, and save/restore. Storage management via storage pools (directory, LVM, iSCSI, NFS, disk, Gluster, RBD, ZFS) and volumes for managing virtual disk images. Network management via virtual networks (NAT, bridged, isolated) and interface management for physical and virtual network interfaces. Snapshot management for point-in-time VM state capture and restore. Migration support for live, offline, and peer-to-peer migration between hosts with storage migration. CPU and memory hotplug for adjusting resources without downtime. XML-based configuration for domains, pools, networks, and other objects with schema validation. virsh command-line tool for interactive and scripted management. Security via SELinux and AppArmor integration, sVirt for VM isolation, and secret storage for passwords and encryption keys. Event API for asynchronous notifications of VM lifecycle events. Remote management via TLS, SSH, TCP, and Unix socket transports with authentication and encryption. Logging and audit subsystem. Used by oVirt, OpenStack, virt-manager, GNOME Boxes, and libguestfs.