How 2 Unpack/pack the android images:

How 2 Unpack the android images:
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1. ./unyaffs system.img  (unpack the yaffs file system.img) yaffs - file system
2.gunzip -c ramdisk.img |cpio -i
3../unpack-bootimg.pl boot.img

To Pack System.img:
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mkyaffs2image tool

./mkyaffs2image ./system (folder) system.img

will creates the system.img from system folder.