The old MBR 512 bytes partition table is no longer valid if you are using GPT. To copy a GPT table with dd to another disk do it like so: Below sda is the source disk and destination disk is sdb (change to meet your needs). Depending on how you use this, you have to be careful. The assumption is that you should only dump the partition table back to a disk you will newly format. If not you'll need to ch........