From Looking Glass
Jump to navigation Jump to search

Looking Glass Client[edit]

This guide will step you through building the looking glass client from source, before you attempt to do this you should have a basic understanding of how to use the shell.

Building the Application[edit]

Installing Build Dependencies[edit]

  • binutils-dev
  • cmake
  • fonts-freefont-ttf
  • libsdl2-dev
  • libsdl2-ttf-dev
  • libspice-protocol-dev
  • libfontconfig1-dev
  • libx11-dev
  • nettle-dev
Debian (and maybe Ubuntu)[edit]
apt-get install binutils-dev cmake fonts-freefont-ttf libsdl2-dev libsdl2-ttf-dev libspice-protocol-dev libfontconfig1-dev libx11-dev nettle-dev
Fedora 29+[edit]
dnf install make cmake binutils-devel SDL2-devel SDL2_ttf-devel nettle-devel spice-protocol fontconfig-devel libX11-devel egl-wayland-devel wayland-devel mesa-libGLU-devel mesa-libGLES-devel mesa-libGL-devel mesa-libEGL-devel libXfixes-devel libXi-devel
OpenSuSE Leap 15.0+[edit]
zypper install make cmake binutils-devel libSDL2-devel libSDL2_ttf-devel libnettle-devel nettle spice-protocol-devel fontconfig-devel libX11-devel libconfig-devel libwayland-egl-devel libXi-devel
Arch Linux / Manjaro[edit]
pacman -Syu binutils sdl2 sdl2_ttf libx11 nettle fontconfig cmake spice-protocol gnu-free-fonts glu
Void Linux[edit]
xbps-install -Syu binutils-devel cmake freefont-ttf SDL2-devel SDL2_ttf-devel spice-protocol fontconfig-devel libX11-devel nettle-devel

First set up the necessary USE flags if needed:

echo "media-libs/libsdl2 gles2" >> /etc/portage/package.use/libsdl2
echo "media-libs/nettle gmp" >> /etc/portage/package.use/nettle

Then fetch the packages:

emerge sys-devel/binutils media-libs/libsdl2 media-libs/sdl2-ttf dev-libs/nettle media-libs/fontconfig dev-util/cmake app-emulation/spice-protocol media-fonts/freefonts media-libs/glu

This list can also be placed into a setfile in /etc/portage/sets/ so that they can be updated with

emerge @setfile


Either visit the site at Looking Glass Download Page

Or pull the lastest bleeding-edge version using the git command.

Note: If you are using the latest bleeding-edge from the master branch you MUST download/use the corresponding host application

git clone --recursive


If you downloaded the file via the web link then you should have a 'zip' file. Simply unzip and cd into the new directory. If you used 'git' then cd into the 'LookingGlass' directory.

mkdir client/build
cd client/build
cmake ../
The most common compile error is related to backtrace support. This can be disabled by adding the following option to the cmake command: -DENABLE_BACKTRACE=0, however, if you disable this and need support for a crash please be sure to use gdb to obtain a backtrace manually or there is nothing that can be done to help you.

Should this all go well you should be left with the file looking-glass-client. Before you run the client you will first need to configure either Libvirt or Qemu (whichever you prefer) and then set up the Windows side service.

You can call the client from the build directory; or, you can make it callable generally by adding the directory to your path or issuing

ln -s $(pwd)/looking-glass-client /usr/local/bin/

from the build directory.

libvirt Configuration[edit]

This article assumes you already have a fully functional libvirt VM with PCI Passthrough working on a dedicated monitor. If you do not please ensure this is configured before you proceed.

If you are using QEMU directly, this does not apply to you.

Add the following to the libvirt machine configuration inside the 'devices' section by running "virsh edit VM" where VM is the name of your virtual machine.

<shmem name='looking-glass'>
  <model type='ivshmem-plain'/>
  <size unit='M'>32</size>

The memory size (show as 32 in the example above may need to be adjusted as per Determining Memory section.

If you would like to use Spice to give you keyboard and mouse input along with clipboard sync support be sure to also do the following:

  • Add a QXL video device, but in the type field type `none` (on older libvirt versions just disable the device in Windows Device Manager)
  • Be sure to remove the virtual tablet pointing device.
  • Be sure to add the virtual PS/2 Mouse device, and the Virtio keyboard device.
  • Be sure that there is also a Spice Display configured (in addition to the video device)

If you want clipboard synchronization please see FAQ#How to enable clipboard synchronization via SPICE


For libvirt versions before 5.10.0, if you are using AppArmor, you need to add permissions for QEMU to access the shared memory file. This can be done by adding the following to /etc/apparmor.d/abstractions/libvirt-qemu.

/dev/shm/looking-glass rw,

Qemu Commands[edit]

If you are using virt manager then this does not apply to you.

Add the following to the commands to your QEMU command line, adjusting the bus to suit your particular configuration:

-device ivshmem-plain,memdev=ivshmem,bus=pcie.0 \
-object memory-backend-file,id=ivshmem,share=on,mem-path=/dev/shm/looking-glass,size=32M

The memory size (show as 32 in the example above may need to be adjusted as per Determining Memory section.

Determining Memory[edit]

You will need to adjust the memory size to a value that is suitable for your desired maximum resolution using the following formula:

width x height x 4 x 2 = total bytes total bytes / 1024 / 1024 = total megabytes + 2

For example, for a resolution of 1920x1080 (1080p)

1920 x 1080 x 4 x 2 = 16,588,800 bytes 16,588,800 / 1024 / 1024 = 15.82 MB + 2 = 17.82

You must round this value up to the nearest power of two, which with the above example would be 32MB

It is suggested that you create the shared memory file before starting the VM with the appropriate permissions for your system, this only needs to be done once at boot time, for example (this is a sample script only, do not use this without altering it for your requirements):

touch /dev/shm/looking-glass && chown user:kvm /dev/shm/looking-glass && chmod 660 /dev/shm/looking-glass

Looking Glass Service (Windows)[edit]

You must first run the Windows VM with the changes noted above in either the libvirt or Qemu sections.

Installing the IVSHMEM Driver[edit]

Windows will not prompt for a driver for the IVSHMEM device, instead, it will use a default null (do nothing) driver for the device. To install the IVSHMEM driver you will need to go into the device manager and update the driver for the device "PCI standard RAM Controller" under the "System Devices" node.

French: "Gestionnaire de périphérique" -> "Périphériques Système" -> "Contrôleur de RAM Standard PCI"

English: "Device Manager" -> "System Devices" -> "PCI standard RAM Controller"

A signed Windows 10 driver can be obtained from Red Hat for this device from the below address:

Please note that you must obtain version 0.1.161 or later

A note about IVSHMEM and Scream Audio[edit]

Using IVSHMEM with Scream may interfere with Looking Glass as it may try to use the same device. Please do not use the IVSHMEM plugin for Scream. Use the default network transfer method. The IVSHMEM method induces additional latency that is built into its implementation. When using VirtIO for a network device the VM is already using a highly optimized memory copy anyway so there is no need to make another one.

If you insist on using IVSHMEM for Scream despite its inferiority to the default network implementation the Windows Host Application can be told what device to use. Create a looking-glass-host.ini file in the same directory as the looking-glass-host.exe file. In it, you can use the os:shmDevice option like so:


Using the Windows Host Application[edit]

Start downloading the correct version for your release from You can either choose between Official Releases which is is stable or Release Candidates that tries to be stable but has new features. Note: If your looking-glass-client was created by building from the master branch you have to pick the Bleeding Edge version.

The windows host application captures the windows desktop and stuffs the frames into the shared memory via the shared memory virtual device, without this Looking Glass will not function. It is critical that the version of the host application matches the version of the client application, as differing versions can be, and usually are, incompatible.

Note: As of 2020-08-12 (commit dc4d1d49fac2361e60c9bb440bc88ce05f6c1cbd), the below instructions are deprecated. The host application now has an installer that installs a system-wide service to run the Looking Glass host application. When upgrading please be sure to remove the scheduled task if you have already created one.

To get the Windows-Host-Application running after restart you need to run it as a privileged task we do that by starting cmd.exe as administrator and running a command in it which creates a windows task.

Note: At this time the Looking Glass host does not support running under unprivileged users. Your user account must have administrator privileges for the windows task to function.

SCHTASKS /Create /TN "Looking Glass" /SC  ONLOGON /RL HIGHEST /TR C:\Users\<YourUserName>\<YourPath>\looking-glass-host.exe

Copy the following command in to your cmd shell and replace the <YourUserName> with your username (e.g. "games") and your <YourPath> with the part where the looking-glass-host.exe is stored (e.g. "Documents") .

Screenshot cmd windowstask.png

Now you simply need to hit enter in to the cmd shell and restart the vm to test if it worked.

Running the Client[edit]

The client command is the binary file: looking-glass-client. This command should run after the Windows Host Application has started.

For an updated list of arguments visit:

Common options include '-s' for disabling spice, '-S' for disabling the screen saver, and '-F' to automatically enter full screen.