== Flash an existing build ==
First [https://www.dropbox.com/s/ul7dk162j7ed0x6/ffos-rpi.img.tar.bz2?dl=0 download the build]. Next extract it as follows
tar jxvf ffos-rpi.img.tar.bz2
That will produce a file called <code>ffos-rpi.img</code>. Now insert your SD card into a card reader/writer. Your OS should add your SD card as a device called something like <code>/dev/mmcblk0</code>, <code>/dev/sdc</code>, or <code>/dev/disk2</code>. Let's call that device <code>$disk</code> below.
<font size="5" color="red">WARNING WARNING WARNING</font>: the remaining steps with <font size="5">COMPLETELY AND PERMANENTLY ERASE YOUR SD CARD</font>. Be extra-triple-careful that you found the right device for your SD card.
Finally, run
dd bs=4M if=ffos-rpi.img of=$device
Note: this disk image is pre-partitioned for a 4GB disk. If you have a larger SD card and want to allocate the remaining space for your SDCARD partition, then resize that partition in a tool like <code>gparted</code>.
== Building b2g for RPi ==