overlayfs testing script

test_overlay.sh

~# cat overlay.sh
#!/bin/sh -e

modprobe overlay

mkdir -p /overlay

mount -t tmpfs tmpfs /overlay

mkdir -p /overlay/blk

mkdir -p /overlay/lower

mkdir -p /overlay/root

mount -t ext4 -o ro /dev/mmcblk1p2 /overlay/lower

mount -t ext4 /dev/mmcblk1p3 /overlay/blk

mkdir -p /overlay/blk/upper
mkdir -p /overlay/blk/work

mount -t overlay overlay -o lowerdir=/overlay/lower,upperdir=/overlay/blk/upper,workdir=/overlay/blk/work /overlay/root

mkdir -p /overlay/root/proc
mkdir -p /overlay/root/sys
mkdir -p /overlay/root/dev

mount -o bind /proc /overlay/root/proc
mount -o bind /sys /overlay/root/sys
mount -o bind /dev /overlay/root/dev

chroot /overlay/root