Fixing Mvix Ultio firmware

I always dreamed of a small NAS with BitTorrent capabilities to replace my noisy and always hot AMD-based HTPC computer. Last week I've received Mvix Ultio (MX-800HD), which I bought on eBay. This box connected to your LAN via either a cable or wireless from one side, and to your TV panel (via HDMI video and optical audio) from the other side, while having a 3.5 SATA disk bundled inside can be turned into a powerful entertainment device (with minimal power consumption).

The first thing I did when I connected this device, is flashing a new firmware v3.0 from Mvix Ultio support site. I enabled BitTorrent client and Samba plug-ins, as was described in manual. At that time I didn't expect any disappointment, but it came soon when I left it on overnight: the device hanged every couple of hours with no possibility to reboot it using remote control or panel buttons. I've read in one forum that unlimited number of peers in a bundled BitTorrent client (btpd) can kill this device easily. I tried to change settings of btpd startup script via telnet, but with no success as /etc is actually mapped to memory, and is not changeable.

Below comes a remedy process based on fixing an existing firmware, and preparing it for further hacking :)

DISCLAIMER: I take no responsibility for any damage you might cause to your device by following this guide.

1. You must have some Linux machine for that (choose yourself, what's easier: installing Ubuntu on VirtualBox or installing Cygwin on Windows? :-])

2. Download, compile and put mkyaffs2image and unyaffs utilities under your $PATH.

3. Extract existing firmware image:

mkdir install
cd install
tar xvf ../intsall.img

4. Extract contents of yaffs2_1.img:

cd package2
mkdir yaffs2_1
cd yaffs2_1
unyaffs ../yaffs2_1.img
cd ../

5. Extract contents of usr.local.etc.tar.bz2 (this archive will be extracted into a writable partition on a device, partition size is controlled by <sizeBytesMin> entry in configuration.xml):

mkdir usr_local_etc
cd usr_local_etc
tar jxvf ../usr.local.etc.tar.bz2
cd ../

The whole idea is to place things that we might need to configure later on a running device into this archive. So I've just merged contents of package2/yaffs2_1/etc/ into this archive (please do it carefully as there are plenty of symlinks pointing to the same place: /usr/local/etc). Then, I removed whole directory package2/yaffs2_1/etc/, and created a symlink instead:

rm -rf yaffs2/etc
ln -s /usr/local/etc yaffs2/etc

6. Now, lets fix the BitTorrent client settings:

vi yaffs2_1/usr/local/bin/package/script/bt.script
# find "start running btpd", and add needed settings after the $btpdbin
# (I've just limited a number of peers by adding: --max-peers 48)

BTW, you can move this script into /usr/local/etc archive too, and create a symbolic link to it, if you wish to modify it later on a running device.

7. Compress usr.local.etc.tar.bz2 back:

cd .usr_local_etc/

# Restore original files ownership (I don't know whether this is crucial):
chown -R 500:500 .

tar jcvf ../usr.local.etc.tar.bz2 *
cd ..
rm -rf usr_local_etc

7.1 (maybe optional) I don't know what's the point in duplicate /usr/local/etc/ folder contents under package2/yaffs2_1/usr/local/etc/, so I just did the following:

cd yaffs2_1/usr/local/etc/
rm -rf *
tar jxvf ../../../../usr.local.etc.tar.bz2
cd ../../../../

8. Compress yaffs2_1.img back:

# Restore original files ownership
chown -R 500:500 yaffs2_1/

mkyaffs2image yaffs2_1 yaffs2_1.img
chmod 644 yaffs2_1.img
rm -rf yaffs2_1

9. Compress the firmware image back:

# Restore original files ownership again :)
chown -R 500:500 .

tar cvf ../install.img *
cd ../
rm -rf install/

That's all. Now you're ready to go, and flash your box with the updated firmware.

PS: I'm too lazy to write how to setup "ipkg" package manager on Mvix Ultio, which allows installing additional software on this device, may be later...