Continuing my week's theme on the XO laptop from the One Laptop Per Child [OLPC] foundation, I successfully managedto emulate my XO on another system.

Part of what is attractive of the XO laptop is the hardware, the high-resolution200dpi screen, the clever screen that rotates and folds flat into an eBook reader,and the water-tight, dust-proof keyboard. The other part is the software, howthey managed to pack an entire operating system, with useful applications, intoa 1GB NAND flash drive.

The drawback for developers like me is the risk of changing something that breaks the system. For example, my first attempt to create my own activityresulted in a blank space in my action bar, and my journal went into someinfinite loop, blinking as if it were still loading for minutes on end. I fixed it by deleting out the activity I created and rebooting.

To get around this, I successfully ran the disk-image under Linux's Virtual Machinesoftware called Qemu. This is an open source offering, with a proprietary add-onaccelerator called Kqemu. Here were the steps involved:

Base Operating System

Qemu is now available to run on Linux, Windows and OS X-Intel. I have an Ubuntu 7.04"Feisty Faun" version of Linux installed on my system from a project I did last year, so decided to use that.

Qemu

Normally, "apt-get install qemu" would be enough, but I wanted to get the latest release, so I downloaded the [0.9.0 version]tarball of compiled binaries. Note that trying to compile Qemu from source requiresa downlevel gcc-3.x compiler, and my attempts to do this failed. The compiled binariesworked fine.

Kqemu

The Kqemu author hasn't packaged this for distribution, so I download the source code anddid my own compiles. You can do the "configure-make-install" using the regular gcc 4.1compiler and it went smoothly.

Getting Kqemu active was bit of a challenge. I had to make sense of Nando Florestan's[Installing Kqumu in Ubuntu] article,and the subsequent comments that followed.

There is a tiny [8MB Linux image]that should be used to verify the Kqemu is activated correctly.

The Disk Image

As with other development efforts, there are the older stable versions, and the bleedingedge development versions. I chose the 650 Build from the [Ship.2 stable versions], whichmatches the version on my XO laptop. The image comes as a *.bz2, which is a highly-compressedfile. Using "Bunzip2", the 221MB file expands to something like 932MB.

I renamed the resulting file to "build650.img"

Once I got all this done, I then made a simple script "launch" in my /home/tpearson/bin directory:

#!/bin/shqemu -m 256 -full-screen -kernel-kqemu -soundhw es1370 -net nic,model=rtl8139 -net user -hda $1

Then "launch build650.img" was all I needed to run the emulation. The full-screen mode helpsemulate the view on XO laptop. I was able to change the jabber server to "xochat.org" and see otherXO laptops online on my neighborhood view.

When running under Qemu, you can't just press Ctrl-Alt-something. For example, Ctrl-Alt-Erase onthe XO reboots the Sugar interface. However, do this on a Linux system, and it reboots your nativeX interface, blowing away everything.Instead, you press Ctrl-Alt-2 to get to the Qemu console, designated by (qemu) prompt,and then type:

sendkey ctrl-alt-backspace

Press "Ctrl-Alt-1" followed by "Ctrl-Alt" to get back to the emulated XO screen.

With this emulation, I am more likely to try new things, change files around, edit system files,and so on, without worrying about rendering my actual XO laptop unusable. Once debugged, I canthen work on moving them over to my XO, one at a time.

technorati tags: OLPC, XO, laptop, Qemu, Kqemu, Ubuntu, Linux, Activity, Journal

Tags:  linux olpc