boot external usb harddrive rootfs

[Elegantuni]

Plug in the usb hard drive.
sudo fdisk /dev/sda
Press o then Press enter
Press n then Press enter then Press enter then Press enter
Press a then Press 1 then Press enter

sudo mkfs.ext4 /dev/sda1
sudo dd if=/dev/mmcblk0p2 of=/dev/sda1 bs=1M

sudo fsck.ext4 -f /dev/sda1
sudo resize2fs /dev/sda1

sudo nano /etc/fstab
Change the numbers before / to /dev/sda1

cd
mkdir harddrive
sudo mount /dev/sda1 harddrive
sudo nano harddrive/etc/fstab
Change the numbers before / to /dev/sda1
sync
sudo umount harddrive

sudo nano /boot/cmdline.txt
Change root=PARTUUID=* and numbers to root=/dev/sda1

Reboot