uuid

A uuid or universally unique identifier is used to identify objects which is 128bit long.

Older versions of Linux have a vol_id utility to display the uuid of a file system.(RHEL 5 puts vol_id in /lib/udev/vol_id, which is not in the $PATH).

The utility is not available in standard installations of RHEL6 or Debian6.

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root@debian:~# vol_id --uuid /dev/sda1
root@rhel5 ~# /lib/udev/vol_id -u /dev/sda1
[root@centos7 ~]# tune2fs -l /dev/vda1 | grep -i uuid
Filesystem UUID:          4b499d76-769a-40a0-93dc-4a31a59add28
[root@centos7 ~]# grep ^[^#] /boot/grub2/grub.cfg