kmsvnc 0.2.2

A KMS/DRM-based VNC server for Linux
kmsvnc-0.2.2 is not a library.

kmsvnc

A lightweight VNC server for Linux that captures the screen directly from the KMS/DRM framebuffer and forwards input via virtual uinput devices. Works independently of any display server — it operates the same whether X11, Wayland, or nothing at all is running.

Features

  • KMS/DRM screen capture — reads the GPU framebuffer directly, works without a display server
  • Dumb buffer fallback — works with simpledrm, vkms, and other drivers that lack PRIME export
  • Linux fbdev fallback — captures from /dev/fb* when DRM is unavailable entirely
  • Minimal RFB protocol — standard VNC clients (TigerVNC, Remmina, KRDC, etc.) connect out of the box
  • Virtual touch input — VNC pointer events are translated to Linux multitouch events via uinput
  • Virtual keyboard — VNC key events are mapped from X11 keysyms to Linux input codes
  • Incremental updates — 64px tile-based dirty rectangle detection to reduce bandwidth
  • Pixel format negotiation — respects client SetPixelFormat requests (any bpp/endianness/shifts)
  • Multiple DRM formats — XRGB8888, ARGB8888, XBGR8888, ABGR8888, RGB565
  • VNC authentication — optional password-based authentication (RFB Security Type 2, DES challenge-response)

Installation

cargo install kmsvnc

To build from source, see BUILDING.md.

Usage

# Run as root (simplest)
sudo kmsvnc

# Or grant capabilities
sudo setcap cap_sys_admin+ep $(which kmsvnc)
sudo usermod -aG input $USER  # for /dev/uinput access (re-login required)
kmsvnc

Then connect any VNC client to localhost:5900.

Options

--device <path>      Capture device path: /dev/dri/card*, /dev/fb* (default: auto-detect)
--port <port>        VNC listen port (default: 5900)
--fps <fps>          Capture frame rate (default: 30)
--listen <addr>      Listen address (default: 0.0.0.0)
--password <pass>    Require VNC password authentication (default: no auth)

Logging

Control log verbosity with the RUST_LOG environment variable:

RUST_LOG=info sudo kmsvnc    # default useful output
RUST_LOG=debug sudo kmsvnc   # detailed diagnostics

Limitations

  • Raw encoding only (no compression — best used on LAN)
  • No encryption (VNC authentication uses DES challenge-response but traffic is unencrypted — use SSH tunneling for security)
  • Uses the first connected display output
  • Clipboard forwarding not implemented

Troubleshooting

See TROUBLESHOOTING.md.