I executed all points and created the file /usr/local/mac_addr.
If "device" in this sentence:
The last thing needed is this: create & edit usr/local/mac_addr on the extracted rootfs, (not this machine you are using to do this!) and place in your device's MAC address in the format XX:XX:XX:XX:XX:XX.
means "pogoplug", how can I find the mac address?