I recently needed to know the UUID (universally unique identifier) of my bootable USB root partition. It is a better way to distinguish storage devices because device names can change depending on the connection order.
There are at least several ways to get UUIDs.
$ ls -l /dev/disk/by-uuid/*
lrwxrwxrwx 1 root root 10 maj 9 18:05 /dev/disk/by-uuid/5d2f85fe-b555-4504-a87f-3d1c6513c7d4 -> ../../sda2
lrwxrwxrwx 1 root root 10 maj 9 18:05 /dev/disk/by-uuid/678e905f-68cc-449e-99a9-cb90d7011d23 -> ../../sdb1
lrwxrwxrwx 1 root root 10 maj 9 18:05 /dev/disk/by-uuid/687aa5e4-3863-4529-a8bf-fa526716f523 -> ../../sdb2
lrwxrwxrwx 1 root root 10 maj 9 18:05 /dev/disk/by-uuid/8252dada-3e65-401b-b0cf-0123a7b62df6 -> ../../sda1
lrwxrwxrwx 1 root root 10 maj 9 18:05 /dev/disk/by-uuid/8b19014d-442a-4e2e-8367-569f000afaa0 -> ../../sda3
$ ls /dev/disk/by-uuid/* | xargs file
/dev/disk/by-uuid/5d2f85fe-b555-4504-a87f-3d1c6513c7d4: symbolic link to `../../sda2'
/dev/disk/by-uuid/678e905f-68cc-449e-99a9-cb90d7011d23: symbolic link to `../../sdb1'
/dev/disk/by-uuid/687aa5e4-3863-4529-a8bf-fa526716f523: symbolic link to `../../sdb2'
/dev/disk/by-uuid/8252dada-3e65-401b-b0cf-0123a7b62df6: symbolic link to `../../sda1'
/dev/disk/by-uuid/8b19014d-442a-4e2e-8367-569f000afaa0: symbolic link to `../../sda3'
$ find /dev/disk/by-uuid/* -exec echo -n {} "-> " \; -exec readlink {} \; | sort -k2 | sed 's/\.\.\///g'
/dev/disk/by-uuid/8252dada-3e65-401b-b0cf-0123a7b62df6 -> sda1
/dev/disk/by-uuid/5d2f85fe-b555-4504-a87f-3d1c6513c7d4 -> sda2
/dev/disk/by-uuid/8b19014d-442a-4e2e-8367-569f000afaa0 -> sda3
/dev/disk/by-uuid/678e905f-68cc-449e-99a9-cb90d7011d23 -> sdb1
/dev/disk/by-uuid/687aa5e4-3863-4529-a8bf-fa526716f523 -> sdb2$ sudo blkid
/dev/loop0: TYPE="squashfs"
/dev/sda1: UUID="8252dada-3e65-401b-b0cf-0123a7b62df6" TYPE="ext4"
/dev/sda2: UUID="5d2f85fe-b555-4504-a87f-3d1c6513c7d4" TYPE="swap"
/dev/sda3: UUID="8b19014d-442a-4e2e-8367-569f000afaa0" TYPE="ext4"
/dev/sdb1: UUID="678e905f-68cc-449e-99a9-cb90d7011d23" TYPE="ext4"
/dev/sdb2: LABEL="home-rw" UUID="687aa5e4-3863-4529-a8bf-fa526716f523" TYPE="ext4"
$ sudo blkid -o list
device fs_type label mount point UUID
-------------------------------------------------------------------------------------------------
/dev/loop0 squashfs (in use)
/dev/sda1 ext4 (not mounted) 8252dada-3e65-401b-b0cf-0123a7b62df6
/dev/sda2 swap (not mounted) 5d2f85fe-b555-4504-a87f-3d1c6513c7d4
/dev/sda3 ext4 /media/disk-1 8b19014d-442a-4e2e-8367-569f000afaa0
/dev/sdb1 ext4 (not mounted) 678e905f-68cc-449e-99a9-cb90d7011d23
/dev/sdb2 ext4 home-rw /home 687aa5e4-3863-4529-a8bf-fa526716f523
$ cat /dev/.blkid.tab
<device DEVNO="0x0700" TIME="1336670951.551604" TYPE="squashfs">/dev/loop0</device>
<device DEVNO="0x0801" TIME="1336671278.523695" UUID="8252dada-3e65-401b-b0cf-0123a7b62df6" TYPE="ext4">/dev/sda1</device>
<device DEVNO="0x0802" TIME="1336670951.552155" UUID="5d2f85fe-b555-4504-a87f-3d1c6513c7d4" TYPE="swap">/dev/sda2</device>
<device DEVNO="0x0803" TIME="1336670951.552241" UUID="8b19014d-442a-4e2e-8367-569f000afaa0" TYPE="ext4">/dev/sda3</device>
<device DEVNO="0x0811" TIME="1336670951.568408" UUID="678e905f-68cc-449e-99a9-cb90d7011d23" TYPE="ext4">/dev/sdb1</device>
<device DEVNO="0x0812" TIME="1336670951.568610" LABEL="home-rw" UUID="687aa5e4-3863-4529-a8bf-fa526716f523" TYPE="ext4">/dev/sdb2</device>
$ cat /dev/.blkid.tab | sed 's/.*UUID="\(.*\)"\ .*>\(.*\)<.*/\1 -> \2/g' | grep -v ^\< | sort -k2
8252dada-3e65-401b-b0cf-0123a7b62df6 -> /dev/sda1
5d2f85fe-b555-4504-a87f-3d1c6513c7d4 -> /dev/sda2
8b19014d-442a-4e2e-8367-569f000afaa0 -> /dev/sda3
678e905f-68cc-449e-99a9-cb90d7011d23 -> /dev/sdb1
687aa5e4-3863-4529-a8bf-fa526716f523 -> /dev/sdb2$ sudo tune2fs -l /dev/sda1 | grep UUID | tail -c 37
8252dada-3e65-401b-b0cf-0123a7b62df6
To change device UUID, use tune2fs and uuidgen commands together:
$ sudo tune2fs -U `uuidgen` /dev/sda3
