I'm trying to reverse engineer an appliance based on RPI2, and I would like to get a root shell on the system.
After dumping the SD I noticed that there's no rootfs partition (it exists but it's empty), and a all the needed files are stored ramdisk inside the boot image.
There's no SSH, UART and not even video console. My idea was to unpack, patch and repack the ramdisk, but it appears to be more difficult than expected: the cpio/gz archives, once repacked (even w/o modifications), have not the same size of the original ones and putting the pieces together results in an unbootable image.
I tried forcing kernel to use an external ramdisk (througth cmdline.txt and config.txt), but it ignores it and keeps using the embedded one.