capability to unmap X11 server from hardware to virtual framebuffer?

Mordechai T. Abzug morty at
Tue Apr 22 19:32:59 PDT 2008

Some issues I've been having with my X servers:

(1) When I'm running multiple X servers on a single Linux box for
    different users, each X server is mapped to a different Linux VT.
    Only one of the X servers is actually active on the video hardware
    at any given time.  But the first X server to start "grabs" the 3D
    acceleration capability of the video hardware, so the second
    session does not get 3D acceleration even when it is the active

(2) If I am using x11vnc to access a display remotely, there is no
    good way to prevent someone physically on console from interfering
    with my session.  Once the session is unlocked for remote use,
    it's also unlocked for local use.

(3) If I am using x11vnc to access an X server display remotely, and
    someone else is using a different display on console or has just
    changed the current Linux VT to a different VT, my remote display
    ceases to work.

I think the solution to all three problems would be a capability to
"unmap"/"remap" an X11 display from the physical hardware, either by a
new API, or when the VT changes.  The framebuffer of an unmapped X
server would be redirected to a virtual framebuffer in RAM, so x11vnc
could work correctly.  xdm (or gdm or kdm) should provide a capability
to recover a live unmapped session.  That would fix these problems.

I emailed the x11vnc author, Karl Runge.  He said he would use such an
API if it were available.


- Morty

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