Get the latest tech news
Virtual Machine Administration Using QEMU Monitor
When a virtual machine is invoked by the qemu-system-ARCH comman…
Using the commands available in the monitor console, it is possible to inspect the running operating system, change removable media, take screenshots or audio grabs and control other aspects of the virtual machine. You can access the monitor console only if you started the virtual machine directly with the qemu-system- ARCH command and are viewing its graphical output in a native QEMU window. If you started the virtual machine with libvirt(for example using virt-manager) and are viewing its output via VNC or Spice sessions, you cannot access the monitor console directly.
Or read this on Hacker News