I built a recovery.img (using flo lunch setup) for my Nexus 7 device using AOSP source code. I can use it like:
$ adb reboot bootloader
$ fastboot boot recovery.img
However, when I unpack and re-pack the recovery.img file using abootimg utility (without making any modifications to ramdisk) and retry to boot using recovery.img, my Nexus 7 simply goes into Google splash screen loop. Device keeps rebooting after coming to splash screen.
For details, here are my steps:
$ ls
recovery.img
$ abootimg -x recovery.img
$ abootimg-unpack-initrd initrd.img
$ abootimg-pack-initrd myinitrd.img ./ramdisk
$ abootimg -u recovery.img -r myinitrd.img
Resulting updated recovery.img doesn't work as intended, even though its simply an unmodified copy of original recovery.img file.