jffs2 :

• http://www.aweiler.com/linux/debianonflash.html
• http://packages.qa.debian.org/m/mtd-utils.html
• maemo http://maemo.org/community/wiki/ModifyingRootImage/

 IMG=rootfs.jffs2
 sudo mkdir -p /mnt/jffs2
 sudo mknod /dev/mtdblock0 b 31 0
 sudo modprobe loop
 sudo losetup /dev/loop0 ${IMG}
 sudo modprobe -v mtdblock
 sudo modprobe -v block2mtd  ### for Linux 2.6.x
 # sudo modprobe blkmtd device=/dev/loop0  ### for Linux 2.4.x
 sudo sh -c 'echo /dev/loop0 > /sys/module/block2mtd/parameters/block2mtd' # Linux 2.6.x
 sudo modprobe -v jffs2
 sudo mount -t jffs2 /dev/mtdblock0 /mnt/jffs2

jffs2: Too few erase blocks (0)