Remote display

If you are trying to project the user interface of an XO laptop, this page is for you. It describes how to bring up the user interface of an XO laptop across the network on another computer running X11 (the display computer).

Changes to the XO (the forwarding or source computer)

There are some harmless changes to the XO which only need to be done once. You will need to assign a password to the olpc user, and create the script which is remotely executed to start Sugar.

To assign a password to the laptop user, obtain a console window (through the debugging interface accessed by alt + "=", or by bringing up a console with ctl + alt + F1/Eye). Become root and change the password by typing:

su
passwd olpc

Now go to the laptop user's home directory, and create the script which will start sugar:

cd /home/olpc
echo "#\!/bin/sh" > remotedisplay
cat .xinitrc >> remotedisplay
chmod a+x remotedisplay

Stopping Sugar on the XO

Due to current limitations of Sugar, there can only be one copy of Sugar running on any given XO. This will mean that you need to shut down Sugar and X on the XO from which you want to forward the user interface. There are several ways you can do this, but the simplest (and temporary) way is to first change to the console, by typing control + alt + F1 (Eye). Log in as root, then change the runlevel of the XO to runlevel 3 by typing:

init 3

After doing this, the XO should still be associated with any wireless network it already found, but it will have forgotten about its IP address. You need to manually request an address using:

dhclient eth0

If this doesn't work because you aren't associated with a wireless network, you can manually bring up the network using:

iwconfig eth0 essid "some local wifi SSID"
dhclient eth0

You can get a list of the local WiFi networks using iwlist.

Remember the network address assigned to the XO by DHCP, you will need it for the next steps.

Bringing up the display remotely

At this point, you will need a version of X on the display computer which is running bare (no display or session manager). The easiest way seems to be to create a new user on the display computer, and give them an .xinitrc (or .xsession file under Debian) which consists simply of:

exec xterm

Log in as the new user, and from that single xterm, you should be able to bring up the display remotely using:

ssh olpc@xo-ip-address -C -X /home/olpc/remotedisplay

Caveats

Modifying WiFi

Whatever you do, don't click on the WiFi signal strength when using the remote display. Even if you select the network you are already using, you will freeze the display.

Screen Resolution

It is unclear what the effects of different display computer screen resolutions will have on the remote display.

Using a Laptop's VGA output

While on Gen1 XO laptops (the B1/B2/B3/C1/MP builds) it will continue to be possible to attach a VGA connector to the XO motherboard, making use of it requires soldering a jumper (pins 1 and 3 of CN18) and cutting the laptop case to make room for it. In B3/C1/MP versions, additional required passive components will not be populated on the motherboard (but are easier to obtain than the required VGA connector!)

One problem with this approach (on B2, but not B3/C1/MP machines) is a weird gamma correction currently applied by software to fix a hardware wiring error.

An additional problem is that many displays are very unhappy with the 1200x900 resultion video output by default by the XO laptop.