i'm trying to unpack a clear spot firmware update

this firmware

http://www.clear.com/support/download/spots/clear-spot-voyager

i used a fwtools to unpack the whole firmware from this page

http://hackspot.net/iSpotBlog/?p=177

after that i have " kernel.bin " and " rootfs.bin "

ok i want to add a new certificate to the modem and new Networks and some edits to the control panel 192.168.1.1 " it's Wimax Modem

when i check the rootfs file with this code

file rootfs.bin

i see this

rootfs.bin: Linux Compressed ROM File System data, little endian size 4280320 version #2 sorted_dirs CRC 0xbf224100, edition 16777728, 268441607 blocks, 1325400384 files

i stopped here , i don't know how to unpack it , i just tried everything manually , firmware mod fit , fwtools , everything !

any help ?