Session Migration With GDM

Last year Caolan
and I demoed hotdesking with GDM and VNC. Owen later pointed out that VNC
probably wasn’t the way to go once the rendering
they’re working come on line.

So, last week I picked up a patch I’d hacked up before Christmas,
finished it off and committed it to GDM. The idea is to do the same
thing as the VNC patch, but this time using a X proxy (like Xnest)
server on the terminal server instead of a VNC server.

Specifically, though, the features added to GDM are:

  • You can now configure GDM to run XDMCP sessions on a local X
    proxy server. This may be useful on its own for performance reasons;
    in theory, at least, an X proxy server should be able to limit the
    number of roundtrips it makes to the remote X server since if all you
    want to do is query server state, then that state is local. I’ve no
    idea yet how well Xnest and others do on this in practice, though.
  • If the proxy server supports disconnecting from its parent
    display and re-connecting later, you can configure GDM such that you
    can disconnect from your session and reconnect later simply by logging
    back in. The only proxy server’s that I know of which support this is
    the DMX X server and NoMachine NX’s nxagent. Its
    certainly possible to do this with any proxy though; I had it half
    done for Xnest before realizing DMX had good enough support to get the
    GDM patch done.

I’ve played around a little today with NoMachine’s proxy. You can try
it out with GDM HEAD up by:

  1. Install NoMachine’s server package
  2. Set xdmcp/EnableProxy=true in gdm.conf
  3. Download these scripts (
    and stick them in /tmp
  4. Set xdmcp/ProxyXServer to
    ProxyXServer=/tmp/ -audit 0 -name NX -geometry
    and xdmcp/ProxyReconnect to
  5. Re-start GDM
  6. From another machine run X -query $server and login
    through the login screen
  7. Run /tmp/ --to :20 on the server to
    disconnect your remote X server from the session
  8. Run X -query $server again on the server, login and you
    should be immediately re-directed to your original session

Evolution Mail Account LDAP Backend For GConf

(Jaysus, thats a very long name for a few hundred lines of

I’ve just finished hacking on what was a really interesting little
project. Basically, its a GConf backend which uses information in
the user’s LDAP entries to generate the mail account configuration for
Evolution. The idea is that if you’ve a large number of users, all you
have to do is stick each user’s email address, incoming mail server and
outgoing mail server in her LDAP entry and Evolution should just
magically work.

I’m really happy with how well this thing turned out. I mean, it
actually works, it didn’t take much code, there wasn’t anything
lurking in GConf or Evo waiting to stab me in the back … and, most
of all, it should actually be very useful.

The code is in evolution-gconf-ldap-backend
in GNOME CVS and more details are in the README.

What’s more, Dave Malcolm has also written some cool
to solve the same problem, but without LDAP.