The new rom must be in the path. To prepare the bittorrent file related to the_new_rom.tar.gz (mean to create the_new_rom.tar.gz.torrent):
export MY_TRACKER_IP=pdaxrom.org
export MY_TRACKER_IP_PORT=6969
cd ~/www.pdaxrom.org
btmakemetafile.py the_new_rom.tar.gz http://$MY_TRACKER_IP:$MY_TRACKER_IP_PORT/announce
Then run the tracker on
www.pdaxrom.org. This tracker doesn't need to host any file. It's a client list manager in fact.
bttrack.py --port $MY_TRACKER_IP_PORT --dfile dstate > logfile &
Now need a first bittorrent client with the file completely downloaded (mean a seed). So on the PC where you already have the_new_rom.tar.gz run this command:
btdownloadgui.py the_new_rom.tar.gz.torrent --saveas ~/www.pdaxrom.org/the_new_rom.tar.gz &
Now you can share the_new_rom.tar.gz.torrent with other people. Their client will connect to your tracker and will download the file from your seed. As long as there will still be seeds or that all parts of the file will be on the network, people will be able to complete their download.
Hoping that I haven't make a mistake in my previous instructions.