rootfs doesn't have anything to do with /dev/mmcblk0p2, or with journals, for that matter. Rootfs is ubifs, so trying any ext* tools on it would be futile. I guess, hoever, that you're talking about OptFS, which indeed, is /dev/mmcblk0p2. But, busybox-power doesn't have anything to do with it, it goes into rootfs. Not that bb-power caused any such problems to anyone, ever /Estel