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Installing Fernsicht

One file contains everything: the app, the stream window, the host and the web viewer.

  1. Download the file Fernsicht-<Version>-x86_64.AppImage from the Releases page, make it executable (file manager: Properties › Permissions, or chmod +x Fernsicht-*.AppImage) and start it.
  2. On the computer you want to control: in the bottom left, under “Dieser Rechner” (this computer), click “Diesen Rechner freigeben” (share this computer). This asks for the administrator password once.
  3. After that, the host runs as a system service (fernsicht-host-agent). It starts at boot and runs independently of the app. It is installed in /opt/fernsicht.
  4. “Freigabe beenden” (stop sharing) removes it again. Keys and pairings in /var/lib/fernsicht are kept.
  5. If you later start a newer AppImage, the app offers to update the host.
  6. On the computer you connect from: start the same AppImage. The shared computer appears in the list. Then pair (see section 4, “Pair and connect”) and connect.

The AppImage bundles its own libraries (FFmpeg, SDL3 for gamepads, WebKit). It takes the graphics drivers (Mesa/VAAPI, NVIDIA, Vulkan) from the system, so that hardware encoding matches the installed drivers. Its FFmpeg (8.1) is built for it with only what Fernsicht uses (packaging/ffmpeg.sh): the distribution it is built on (Ubuntu 24.04, for a wide range of systems) has one too old for Vulkan Video.

From source

There are two parts:

  • The app on every computer you connect from. It finds the computers on the network, pairs with them and opens sessions.
  • The host service on every computer you connect to. It starts with the computer and runs in the background.

A computer can have both.

1. Build

Do this once per computer (or after a git pull). The script runs in the Distrobox fernsicht and enters it by itself:

cd ~/fernsicht
./packaging/build.sh

Bazzite ships FFmpeg, libva and WebKitGTK itself. The programs built in the box therefore run directly on the system.

2. Install the app

Without sudo, for your own user:

./packaging/install-app.sh

After that, Fernsicht appears in the start menu. The script puts the app and the client into ~/.local/bin and sets up the start menu entry and the icon. With --uninstall it removes both again.

3. Install the host service

On the computer you want to control remotely:

sudo ./packaging/install-host.sh

Fernsicht-Host läuft. Gerät koppeln: fernsicht-host-agent pair

The script does the following:

  • It copies the program to /usr/local/bin.
  • It sets up the fernsicht-host-agent service (unit) and starts it.
  • If firewalld is running and UDP port 47800 is closed, it opens the port.

Updating works the same way: build again and run the scripts again.

This is how the service runs:

  • Video: The service captures the monitor over KMS. For this it runs as root.
  • Encoder: The service picks the encoder that matches the graphics card (--encoder auto): VAAPI on AMD/Intel, NVENC on NVIDIA. Both take the screen straight from the GPU (KMS capture, no CPU copy); on NVIDIA the picture goes from KMS through Vulkan to CUDA (KMS capture). So a computer with an NVIDIA card works as a host as well as a client.
  • Mouse and keyboard: The service accepts input from paired devices (--input).
  • Audio: The service takes the audio and the monitor layout from the logged-in user. So it captures what runs on that user's desktop.
  • Graphics card: During a session the service keeps the graphics card at full clock speed (AMD: power_dpm_force_performance_level set to high, Intel: minimum clock raised). Otherwise the card would clock down between two frames, and encoding would take longer. Afterwards the service restores everything, also when it is stopped or restarted mid-session; after a crash or a kill it does so when it starts again (it notes the old values in /var/lib/fernsicht/gpu-power.json). To turn this off: in the app under “Einstellungen › Dieser Rechner als Host” (settings › this computer as host), or with --no-gpu-boost.

4. Pair and connect (in the app)

  1. On the host: open Fernsicht and, in the bottom left under “Dieser Rechner” (this computer), click “Gerät koppeln” (pair device). The app shows a 6-digit PIN that is valid for 5 minutes.
  2. On the other computer: open Fernsicht. The host appears in the list. Click “Koppeln” (pair) there and enter the PIN.
  3. Connect: click Desktop. The video opens in its own window, and the app shows the latency.
  4. Ctrl+Alt+Shift+F toggles full screen.
  5. Ctrl+Alt+Shift+Q or “Trennen” (disconnect) in the app ends the session.

You only pair once per pair of devices. You can do the same in the terminal, as the following sections show.

In the browser

You can also connect from a browser, without installing anything, from any computer, tablet or phone on the same network. See the web viewer page.

Gaming

In the app, choose Gaming for a device:

  • Mouse pointer: A click into the window captures the pointer. It then moves relatively, as games need it. Ctrl+Alt+Shift+M captures and releases the pointer, also in desktop mode.
  • Controllers on the client computer are passed through automatically, up to four. On the host they appear as Xbox 360 controllers, PlayStation pads as DualSense pads with gyro and touchpad.
  • Settings (the “Einstellungen” (settings) page): resolution, frame rate (up to 144) and a bitrate limit. The host lowers the bitrate by itself when the network cannot keep up.

Find hosts on the network

On a client computer:

fernsicht-client discover

zentrale  192.168.178.87:47800  Bazzite · Radeon RX 7700 XT / 7800 XT · AV1  paired

The client sends a broadcast query into the local network and also asks the paired hosts directly. No extra port is needed for this; it runs over the same UDP port 47800. If a paired host has a new address in the meantime (DHCP), the client remembers the new one.

The answers are not authenticated. Only the key check during connection verifies that the other end really is the paired host. So a fake entry in the list cannot do any harm.

Pair devices

On the host, without sudo:

fernsicht-host-agent pair

Pairing open for 5 minutes. PIN: 482913
Auf dem neuen Gerät: fernsicht-client pair <diese Adresse> <PIN>

On the new device, with the name from discover or the address:

fernsicht-client pair zentrale 482913

Only root and the user logged in at the desktop may pair. The service checks this through the Unix socket (/run/fernsicht/control.sock). Other users on the same computer are rejected.

Overview and removing devices

fernsicht-host-agent status

Host zentrale (key 3f2a-…)
Connected: bazzite (192.168.178.20:51234), 2560×1440 at 60 fps, encrypted
Paired devices: 1
  bazzite  9c41-…

To remove a device:

fernsicht-host-agent unpair bazzite

After that, this device can no longer connect until it is paired again.

Log, stop, uninstall

journalctl -u fernsicht-host-agent -f        # follow the log
sudo systemctl stop fernsicht-host-agent     # stop (starts again at the next boot)
sudo systemctl disable --now fernsicht-host-agent   # stop and no longer start automatically
sudo ./packaging/install-host.sh --uninstall       # remove completely

Keys and pairings are stored in /var/lib/fernsicht and are kept when you uninstall. If you delete the file host.json there, the host gets a new key. All devices must then be paired again.

If the service reports libavcodec.so.NN: cannot open shared object file after a Bazzite update, the FFmpeg major version has changed. Then update the box (dev/setup.sh), build again and install again.