KVM is an free and open source virtualization solution in a kernel module. Although it is often simply referred to as KVM, the actual hypervisor is QEMU. QEMU runs from user-space, but can integrate with KVM, providing better performance by leveraging the hardware from kernel-space. QEMU can virtualize x86, PowerPC, and S390 guests, amongst others. Libvirt is a management framework that integrates with QEMU/KVM, LXC, Xen and others.
The following commands provide libvirt as well as QEMU with emulation for x86_64 and qemu-img, a necessary component for using various disk formats such as qcow2. Without qemu-img, only raw disks are available. It can also convert images between several formats like vhdx and vmdk.
By default, libvirt uses NAT for VM connectivity. If you want to use the default configuration, you need to load the tun module.
If you prefer bridging a guest over your Ethernet interface, you need to make a bridge.
For (non-root) management, you will need to add your user to the libvirt group.
The libvirt project provides a GUI for managing hosts, called virt-manager. It handles local systems as well as remote ones via SSH.
In order to use libvirtd to remotely control KVM over ssh PolicyKit needs a .pkla informing it that this is allowed. Write the following file to /etc/polkit-1/localauthority/50-local.d/50-libvirt-ssh-remote-access-policy.pkla