I got fed up with Ubuntu's crappy UI, so I went back to basics, but the default new window manager stuff gave me a small, mirrored desktop across both my monitors.

To save someone else the grief, here's a quick how-to:

1) Add a new window manager for rio. Your paths will vary.

~ $ cat /usr/share/xsessions/rio.desktop

[Desktop Entry]

Encoding=UTF-8

Name=rio

Comment=

Exec=/home/plalonde/plan9port/bin/rio.sh

Icon=

Type=Application

~ $

2) Fill in rio.sh to use xrandr to set up your display, and run whatever init you prefer:

~ $ cat plan9port/bin/rio.sh

#!/bin/sh

xrandr --output LVDS1 --mode 1600x900

xrandr --auto --output HDMI1 --mode 1920x1200 --right-of LVDS1

/home/plalonde/plan9port/bin/plumber &

/home/plalonde/plan9port/bin/rio

~ $

Replace LVDS1 and HDMI1 with the names of your video outputs, as reported by "xrandr -q"

That should be enough for demuddling the desperate and sufficient for the method to be indexed for posterity.

Paul