16.04 - How to find UUID for setting up LUKS with keyfile protection for external drive - Ask Ubuntu

i have external drives setup luks + password. increase security password + keyfile. internal storage seems trivial i'm not sure how approach external drive. /dev/sdx seems poor choice external drives , can't find uuid usb-drive.

i've tried:

• blkid - gives uuid local luks drives e.g. `/dev/sdc1' not of external drives luks
• the sudo dmsetup deps -o devname returns drives e.g. (sde) , (sdc1) no uuid.
• cat /proc/mounts gives me luks mappers mounted not more detailed.
• i've tried unmounting drive didn't , drive seems still mapped in /dev/mapper

using lsblk suggested alexp

the lsbslk output give uuid isn't trivial interpret:

name           maj:min rm   size ro type  mountpoint          name           mountpoint          uuid sda              8:0    0   477g  0 disk                      sda                                 ├─sda1           8:1    0   512m  0 part  /boot/efi           ├─sda1         /boot/efi           f2bb-f970 ├─sda2           8:2    0 412,5g  0 part  /                   ├─sda2         /                   4d1c2b61-d9eb-4a3f-b4cf-fae15479670c └─sda3           8:3    0  63,9g  0 part                      └─sda3                             31b267cb-c89f-4662-a68b-74667fb26b48   └─cryptswap1 252:0    0  63,9g  0 crypt [swap]                └─cryptswap1 [swap]              b854bc4f-e822-4917-9373-18eba9b2eb35 ... sde                                                                                              1a3d7d94-373e-4087-aadd-0b3ce09078b5 └─luks-1a3d7d94-373e-4087-aadd-0b3ce09078b5                252:4    0  16,4t  0 crypt /media/musr/ext_icy └─luks-1a3d7d94-373e-4087-aadd-0b3ce09078b5                                                                             /media/musr/ext_icy  42d1104f-3a51-4950-ac70-f3ea1148760c 

it looks there 2 uuid's reported sde - 1 drive , 1 mounted luks

sudo lsblk -o +name,mountpoint,uuid 

the sudo important show unmounted partitions.

disks don't have uuids, partitions do. uuids metadata need stored on partition in format understood system. system understands uuid of partitions formatted ext3, ext4, swap, luks, fat, lvm , on. on disks use relatively new gpt partition table, partitions have partuuid stored in partition table, , can access them entries in /dev/disk/by-partuuid/.