*IMPORTANT UPDATE*
The original instructions listed below were causing my system to randomly go into read-only mode. Use the following instructions instead:
- Download usb-boot.zip and extract the file named mbr2gpt
- Make the file mbr2gpt executable and run it from a system that didn’t boot off of the disk that you are about to convert. For example, if you booted to a USB flash, run ‘sudo mbr2gpt /dev/sdb’ if sdb is the disk that you would like to convert to GPT.
ORIGINAL INSTRUCTIONS (Only shown for informational purposes. DO NOT USE!)
The Pi will boot from a USB drive formatted with GPT. I took the following steps – there may be a better/more efficient way, but this works as a proof of concept:
1. Find out the size of your /boot partition, in sectors. If you’re currently booting from SD, “sudo fdisk -l /dev/mmcblk0p1” will tell you this; mine was 524288 sectors (with a sector size of 512 bytes).
2. Partition your USB drive using the GPT scheme in fdisk. This will erase everything on the drive, so make sure there’s nothing on there that you need.
3. Create a first partition at the beginning of the disk, and be sure it’s the same size in sectors as your existing boot partition.
4. Set the first partition’s type to “Microsoft basic data” (type number 11)
5. Create a partition for your root filesystem to live on, plus any other partitions you want.
6. Unmount your boot partition and use dd to copy it over: “sudo dd if=/dev/mmcblk0p1 of=/dev/sda1” Replace the partition names with your actual partitions if they differ.
7. Format your new root filesystem, ready to accept data, eg “mkfs.ext4 /dev/sda2” (assuming sda2 is your new root partition)
8. Copy across your existing filesystem:
$ sudo mkdir -p /mnt/new
$ sudo mount /dev/sda2 /mnt/new
$ sudo rsync -avHAX / /mnt/new/ --exclude=/boot --exclude=/mnt --exclude=/dev --exclude=/proc --exclude=/sys
$ sudo mkdir -p /mnt/new/{boot,mnt,dev,proc,sys}
$ sudo mount /dev/sda1 /mnt/new/boot9. Edit /mnt/new/boot/cmdline.txt and change “root=/dev/mmcblk0p1” to “root=/dev/sda2”
10. Edit /mnt/new/etc/fstab and change the lines with /dev/mmcblk0* to use /dev/sda* instead.
The USB drive now contains a clone of your Pi filesystem – turn off the Pi, take out the SD card, and when you turn it back on it should boot up exactly as normal, except from your nice big new drive!
If you need to rename your Linux user, just issue the following commands after logging in as the root user:
# usermod -l <new-name> <old-name>
# usermod -d /home/<new-name> -m <new-name>
# groupmod -n <new-name> <old-name>
Reference
https://forums.raspberrypi.com/viewtopic.php?t=319435
https://forums.raspberrypi.com/viewtopic.php?t=196778
