GPT partition tables are necessary on devices whose size is over 2TB.
boot-gpt converts an MBR partition table on a USB device to a GPT partition table, as well as adding or removing a Hybrid MBR (required for direct booting on a Raspberry Pi 3), expanding the ROOT partition, enabling booting via an SD card, and enabling SSH on the next boot. boot-gpt converts any size USB device, including SD cards placed in a USB adapter (an SD card with a GPT partition table also requires a Hybrid MBR for booting).
!!! DO NOT PROCEED UNLESS YOU HAVE A RELIABLE BACKUP OF THE DEVICE BEING CONVERTED !!!
!!! INITIAL TESTING SHOULD BE PERFORMED ON A USB DEVICE CONTAINING EXPENDABLE DATA !!!
Usage syntax is:
boot-gpt will prompt for permission to perform the following optional functions:
1. Use Hybrid MBR (required for direct booting on a Raspberry Pi 3)
2. Expand ROOT partition to use all available space
3. Set SD card to boot the USB device
4. Enable SSH on next boot