I found dtb_id in create-jetson-nano-sd-card-image.sh can be a01 and a02. What make this difference?
It depends on your module. Nano has A01/A02 module revision and I believe most of users here are using A02. This is very common that there is different sku. For example, TX2 is released as c03 in the beginning and later there is something called D01.