locating the UUId of a disk on Linux
the following command will return the UUID of a disk which can be used for ensuring that the correct disk is used for bootup.
osmc@osmc:~$ sudo blkid /dev/sda
/dev/sda: UUID="fcfdb740-7a55-4327-b78e-797691e1c4d6" TYPE="ext4"
in the device example we are using a raspberry-pi.
osmc@osmc:~$ cat /boot/cmdline.txt
root=UUID=002abe1f-7fc0-4bc6-b654-fec3fcb2496e rootfstype=ext4 rootwait quiet osmcdev=rbp2