/dev/mmcblk0p1     *     boot1       Win95 FAT32 (LBA)     vfat
/dev/mmcblk0p2     *     boot2       Win95 FAT32 (LBA)     vfat
/dev/mmcblk0p3           rootfs      Linux                 ext4
/dev/mmcblk0p4           -           Extended              -
/dev/mmcblk0p5           app         Linux                 ext4
/dev/mmcblk0p6           update1     Linux                 ext4
/dev/mmcblk0p7           update2     Linux                 ext4
/dev/mmcblk0p8           persistant  Linux                 ext4

TOP
|       persistant ==> rw+wh
|       update     ==> ro+wh
|       app        ==> ro+wh
V       rootfs     ==> ro+wh
BOTTOM

mount /dev/mmcblk0p7 /mnt
mount -t aufs -o remount,add:0:/mnt=rw+wh none /

[DO MY STUFF HERE]

mount -t aufs -o remount,del:/mnt none /
umount /mnt

# mkdir /testdir
# touch /testfile
# touch /testdir/testfile
# mkdir /etc/testdir
# touch /etc/testfile

[REBOOT on ramdisk without mounting anything]

# mount /dev/mmcblkp7 /mnt
# ls /mnt
lost+found  testdir     testfile
# ls /mnt/testdir
testfile
# umount /mnt
#
# mount /dev/mmcblkp8 /mnt
# ls /mnt/etc
testdir testfile
# umount /mnt