LookingGlass

Looking Glass is a tool that lets you see the screen of a virtual machine on your main monitor with almost no visible delay. It is designed for a specific setup: you have a physical computer running Linux, and inside that computer you are running a virtual machine (a software-simulated second computer) that has been given direct access to a real, dedicated graphics card. That arrangement is called VGA PCI Passthrough, and it lets the virtual machine use the graphics card at full speed rather than through the slower path that typical virtual machines use.

The problem this solves is display output. When a virtual machine has direct control of a graphics card, that card's output normally goes to a separate physical monitor. Looking Glass captures the frames from that card and relays them back to your main screen in real time, so you can use both operating systems on one display without switching cables or monitors.

The technology at the core is called KVM FrameRelay (abbreviated KVMFR). KVM is the Linux virtualization system that hosts the virtual machine. FrameRelay is the mechanism Looking Glass uses to move screen frames from the virtual machine back to the host system with very low latency.

The README for this project is brief. It points to the project website and documentation for setup instructions and directs users to download a source archive rather than build from the raw repository. Full details on installation and configuration live in the external documentation at the project site.