I think it has been discussed and I remembered fanoush has posted as:

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1. copy flash to mmc2

mount -t jffs2 /dev/mtdblock4 /opt

./initfs_flasher/mkfs.jffs2 -r /opt -o /media/mmc2/rootfs.jffs2 -e 128 -l -n

umount /opt

./initfs_flasher/sumtool -i /media/mmc2/rootfs.jffs2 -o /media/mmc2/rootfs.faster.jffs2 -e 128KiB -l -n

2. to restore

./initfs_flasher/flash_eraseall -j /dev/mtd4

./initfs_flasher/nandwrite -a -p /dev/mtd4 /media/mmc2/rootfs.faster.jffs2
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