How to backup(restore) Mac OS image to a hard disk?

• Get a Thunderbolt SATA controller device, and attach a hard disk. Connect the Thunderbolt  cable to your Mac Book.
• Turn ON the Power with the Mac Book, and Press the "Option" Key. That will show boot device menu.

• Choose the "Disk Utility" Item.

• And then erase the HDD.

• You can rename it or use the default name.

• confirm the erasing step.

• Restore item is for backup the Mac OS to a free Hard Disk.

• Start to restore.

• Clear all data.

• Remaining time will be showing up.
• Completed and reboot the system. Then press the "Option" Key and choose the backup HDD, verify whether it can be booting up.  

• Check the name of the booting HDD.