I have extracted the boot image, made the changes that i needed, then used cpio to repack the files, then gziped the image.
When I run rkcrc, all seems fine, but after flashing the new boot.img over its a no go.
# find . | cpio --create --format='newc' > /tmp/newboot
# gzip newboot
# rkcrc -p newboot.gz boot.img
I had to modify the rkcrc sourcecode to get it working on my fview 7" pro tablet
for the fview 7" the rom uses/checks for the header tag "KRNL", different brands might use differend HEADER's
--- check 1 ---
To see if rkcrc works for you
* extracht the "raw" cpiofile from the boot.img
- aka remove the first 8 bytes and last 4 bytes
p.s. at this point the the cpio file should unpack without errors/warnings
* apply rkcrc to the raw cpio
If everything works as it should the original boot.img and new boot.img should be identical, if not there no use i going on,because the bootload will refuse the boot.img.
--- check 2 ---
unpack and recreate the boot.img without any modification
the boot.img should work (and boot)
* Modifying boot.img can be a very tricky thing, a minor mistake can result in your device not booting
* Als using adb logcat during boot can give a lot of information on the boot process, and where it failes
Try it first of a working rom , because there are ofter a lot of errors/warning during the boot process that are "normal"