the right way to create a chromiumos rootfs for beagleboard ?

We noticed there is beagleboard overlay in chromium source and
successfully build the chromiumos_image.bin after process whole step
by step procedure introduced on the official site.

As next the step, we need to use the script to
create two partitions on sd card, one is for Kernel image(fat32) and
the other for rootfs(ext3). The problem is arised in this step, requires a input argument of the path of the tarred
rootfs. in order to get this, I mount the chromium_image.bin with
certain offset indicating in, and then pack the
whole thing as our tarred rootfs. Unfortunately, with this rootfs, we
always get stuck after the kernel successfully mount the second
partition as rootfs. We don't even know whether it found the init
process or not. Can some body who have successfully tried chromiumos
on beagle board share your experience of how to make the correct
chromiumos rootfs on sd card?