Virsh is the command line interface for libvirt.
In most distributions it is installed with libvirt.
sudo apt-get update && sudo apt-get install libvirt
If you are using the good ol' yum.
sudo yum install libvirt
If you are using the new dnf.
sudo dnf install libvirt
sudo zypper ref && sudo zypper install libvirt
sudo pacman -S libvirt
General help
virsh --help
Help for a specific command
virsh <command> --help
Show running Domains / VMs
virsh list
Show all Domains / VMs
virsh list --all
Start an existing domain
virsh start <domain>
Gracefully Shutdown a domain
virsh shutdown <domain>
Hard stop a domain
virsh destroy <domain>
Gracefully Reboot a domain
virsh reboot <domain>
Hard reset a domain
virsh reset <domain>
Edit a domain
virsh edit <domain>
Remove a domain (disk and logs must be deleted manually)
virsh undefine <domain>