UUID (Universally Unique Identifier) is used to identify storage devices on a system. When you add the file system we will add uuid or label.

We can easily generate the UUID in a system using uuidgen command



# uuidgen



d64303a4-2d7d-49ce-b8b4-1fd5db8d444a

How to change the UUID for Logical Volume:

Find out current lvm uuid:

To determine the UUID for the device /dev/mapper/vg01-linux01, can get using blkid command,



# blkid /dev/mapper/vg01-linux01

 

/dev/mapper/vg01-linux01: UUID="4ed7925b-b35a-43ca-abd1-e9db6fb80364" TYPE="ext4"

The output is device name, label name, UUID and file system type ext4

Generate New UUID.


# uuidgen



45ce9e8c-4993-4247-b08b-e8092b898b7e
 
Using tune2fs command can be changed the UUID for that specific device name.


# tune2fs /dev/mapper/vg01-linux01 -U 45ce9e8c-4993-4247-b08b-e8092b898b7e



tune2fs 1.42.8 (20-Jun-2013)

After changes you can check it .


# blkid /dev/mapper/vg01-linux01



/dev/mapper/vg01-linux01: UUID="45ce9e8c-4993-4247-b08b-e8092b898b7e" TYPE="ext4"


How to change the UUID for Partition:

For example, do you want to change the device  /dev/sda1 follow the steps,


#uuidgen

08ad6121-a3a7-4207-9778-ae17f1d55dc4



# tune2fs /dev/sda1 -U 08ad6121-a3a7-4207-9778-ae17f1d55dc4

tune2fs 1.42.8 (20-Jun-2013)



# blkid /dev/sda1

/dev/sda1: UUID="08ad6121-a3a7-4207-9778-ae17f1d55dc4" TYPE="ext4"

Once you have changed that should be update in file system /etc/fstab

UUID Help:


# uuidgen --help



Usage:

 uuidgen [options]



Options:

 -r, --random     generate random-based uuid

 -t, --time       generate time-based uuid

 -V, --version    output version information and exit

 -h, --help       display this help and exit

To find out uuidgen version,


# uuidgen -V

uuidgen from util-linux 2.20.1

How to generate UUID using PHP code,


<?php

echo exec('uuidgen');

?>