Hi garretzou,
For new r32.2 release need add UUID partition.
Below is detail steps for flash on sdcard:
1). Create GPT and partition using gdisk on the external device
2). Get the UUID for the partition on the external device. For example, if the device partition is /dev/sda1, then execute ...
$ sudo blkid /dev/sda1
/dev/sda1: UUID="93A6-26BA" TYPE="vfat" PARTLABEL="Linux filesystem" PARTUUID="018eff62-2d07-4ca5-8619-c30c18b0a181"
3). Write the PARTUUID shown from the previous command to the following file ...
echo '018eff62-2d07-4ca5-8619-c30c18b0a181' > bootloader/l4t-rootfs-uuid.txt
4). Copy the rootfs folder to your sdcard (/dev/sda1)
5). Flash the board: (external is for sdcard, usb and sata)
$ sudo ./flash.sh jetson-tx2 external