crypttab
This configuration allows us to automatically unlock but not mount external drives. For example:
/etc/crypttab
diskn UUID=<path to disk by /dev/disk/by-uuid> /etc/keyfiles/<keyfile name> luks,nofail
This configuration will use the keyfile /etc/keyfiles/keyfile to /dev/disk/by-uuid/id and create a device node for that disk at /dev/mapper/diskn for mounting in fstab.
Do not directly mount the disk