A VNC connection can authenticate successfully and still show a black rectangle or a movable cursor over nothing.
What does a VNC black screen actually mean?
An authenticated connection can still show a black screen. IETF RFC 6143, The Remote Framebuffer Protocol (March 2011, sections 7.3 and 7.5) describes initialization and framebuffer updates separately. Record whether you see a cursor before changing configuration.
Collect facts before changing configuration: echo $XDG_SESSION_TYPE, loginctl list-sessions, and ps -ef | grep -E 'Xorg|wayland|vnc'. Run display commands inside the affected user’s session where possible. Root may see different environment variables and authorization cookies.
Is a display detected?
Cause 1: headless GPU with no display attached
Console-mirroring servers depend on a display mode produced by the graphics stack. The server can accept VNC clients but has no framebuffer with a usable width and height. Check /sys/class/drm/*/status and compositor logs for disconnected outputs or mode-setting errors.
The Linux kernel 6.8 documentation describes the video= parameter for forcing a display mode (Linux 6.8 fb/modedb documentation). Ubuntu 24.04 LTS lists xserver-xorg-video-dummy version 1:0.4.0-1build1 as an X.Org dummy display driver (Ubuntu noble package index).
For Ubuntu 24.04 LTS, the Xtigervnc(1) manual supplied by tigervnc-standalone-server 1.13.1+dfsg-2build2 describes a “virtual” screen rather than a physical one.
Display server
Cause 2: Wayland sessions
Record the compositor and capture tool in use. See the separate VNC on Wayland guide for that topic.
Which layer should you check first?
| Symptom variant | First check |
|---|---|
| No display attached (headless), with or without a movable cursor | Display detection |
| Black with a movable cursor and a display attached | Compositor and capture-tool identification |
For a community report, include the operating system, VNC package version, and symptom variant.
Related guide: VNC connection refused.
Discuss this in the community
Black screen on headless Raspberry Pi 5 after upgrade, cursor only
Sources accurate as of 30 September 2026.
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