There are many ways to generate an Universally Unique Identifier or UUID in Linux. Not long after I wrote my post about my discoveries on DRBD with Corosync and iSCSI, I discovered that I have to define SCSI serial numbers for each of my LUNs.

I decided to have them randomly generated in order to make sure they’re unique. The easiest way is to generate a random UUID. In Linux, you have usually three ways of doing so.

The kernel random way

I chose to use the generator provided by the Linux kernel by using the #!text /proc/sys/kernel/random/uuid file. The contents of the file are a simple UUID :

$ cat /proc/sys/kernel/random/uuid
4fe4772f-e88e-4e10-b072-189a6444fe2c

The uuidgen way

Another method of generating UUIDs is to use the #!shell uuidgen  utility, provided by default in most distributions. This utility is able to generate either random identifiers, or use time as a basis. It can be used as follows :

# Generate a totally random UUID
$ uuidgen
3de197c8-0da3-45e6-8928-11d2be1ec308

# Generate a time-based UUID
$ uuidgen -t
b5646b86-6616-11e4-8035-be3585e0bc43