Libvirt is an open-source API and toolkit designed for managing virtualization platforms such as KVM, QEMU, Xen, LXC, and VirtualBox. It provides a unified interface for creating, configuring, and controlling virtual machines (VMs), regardless of the underlying Hypervisor. Libvirt is widely used in enterprise environments, data centers, and development labs due to its flexibility and robustness.

The primary command-line utility for interacting with libvirt is virsh, which enables comprehensive VM management directly from the terminal without the need for a graphical interface.

Virsh: The Command-Line Interface for VM Management

Virsh is a powerful CLI tool that communicates with the libvirtd daemon and provides full control over VMs. It is ideal for server environments, automation scripts, and headless operation.

Common virsh commands include:

• virsh list --all – list all virtual machines

• virsh start <name> – start a virtual machine

• virsh shutdown <name> – gracefully shut down a VM

• virsh define /path/to/file.xml – define a new VM from an XML file

• virsh console <name> – connect to the VM console

• virsh snapshot-create-as <name> – create a snapshot of a running VM

Virsh can also be used for remote management over SSH or TLS and supports both local and remote hypervisors.

Key Advantages of Using Libvirt and Virsh

• Standardization – consistent interface across different virtualization technologies

• Automation – easy integration with scripts and CI/CD pipelines

• Security – supports TLS encryption, SSH access, and SELinux/AppArmor restrictions

• Advanced features – including live migration, snapshots, and disk cloning

• Hypervisor agnostic – supports KVM, QEMU, Xen, LXC, and more from a single interface

Example: Creating and Starting a VM Using Virsh and Libvirt

1. Create an XML configuration file (e.g., vm.xml):

   <domain type='kvm'>
     <name>test-vm</name>
     <memory unit='MiB'>1024</memory>
     <vcpu>1</vcpu>
     <os>
       <type arch='x86_64'>hvm</type>
       <boot dev='hd'/>
     </os>
     <devices>
       <disk type='file' device='disk'>
         <source file='/var/lib/libvirt/images/test.img'/>
         <target dev='vda' bus='virtio'/>
       </disk>
       <interface type='network'>
         <source network='default'/>
       </interface>
       <graphics type='vnc' port='-1'/>
     </devices>
   </domain>
   

2. Define the VM in libvirt:

   virsh define vm.xml
   

3. Start the virtual machine:

   virsh start test-vm
   

Remote Management with Libvirt

Libvirt supports remote virtualization management using various protocols. To connect to a remote hypervisor over SSH:

virsh -c qemu+ssh://user@remote-system/system list

This allows for full VM management on remote hosts without a GUI, which is essential for headless servers and automation workflows.

Libvirt and virsh offer a powerful, flexible, and open-source solution for managing virtual machines on Linux. They provide full control over VM lifecycle, networking, storage, and more—without the overhead of a graphical interface. Whether you're building a private Cloud or running virtualized workloads on bare-metal servers, libvirt is a mature and reliable foundation for virtualization management.