UUIDs is very helpful to known as identifier for block devices in Linux and its  represented by 32 hexadecimal digits probably  128 bit long numbers.

On this post can generate UUID in three types of command line,

uuidd
uuid
uuidgen

uuidd

Before generate UUID need to execute the below command and check your process status,

# uuidd -p /tmp/uuidd.pid -s /tmp/uuidd.socket

# ps aux | grep uuidd
libuuid  28003  0.0  0.0   3376   308 ?        Ss   18:24   0:00 uuidd -p /tmp/uuidd.pid -s /tmp/uuidd.socket

also see the process id (PID)
# cat /tmp/uuidd.pid
   28003

Generate UUID maximum 5 ID's
 
# uuidd -d -r -n 5 -s /tmp/uuidd.socket


List of UUIDs:

    a9fc32f6-d3cb-4534-984d-aad10f9f53da

    3f88d69c-4d7f-40ed-aea0-3a6f7611cf92

    358f2637-b906-48f7-abe5-e796b04e574f

    c2e1770e-8490-4f2b-861c-dfd63582342e

    c0796a9a-7b5b-4e3b-a67c-6e96d57439d5

To terminate the uuidd process, if you unable to get it can kill the process directly,
 
# uuidd -d -s -k  /tmp/uuidd.socket

# kill -9 28003

uuidgen
 
# uuidgen


c41b33a2-471c-4048-a1e3-8b2dc1a761d8
# for i in `seq 1 5`; do uuidgen; done


431139f6-4fb3-4487-88cc-89610eb946ac

cc878f94-523f-4544-b15a-ea4a580b08a2

e7ec8f7e-95bf-43e3-bf46-60baecde412e

bd3f6ecf-8cd0-4d9e-b8cd-c0ac81426321

86b97bc7-73e1-44e7-ac65-bfae84d3ff6b

Generate time-based uuid
 
# for i in `seq 1 5`; do uuidgen -t; done


9e55f162-4000-11e4-b963-50b7c35a1e6e

9e566048-4000-11e4-b963-50b7c35a1e6e

9e56d46a-4000-11e4-b963-50b7c35a1e6e

9e57438c-4000-11e4-b963-50b7c35a1e6e

9e57b11e-4000-11e4-b963-50b7c35a1e6e

Generate random-based uuid
 
# for i in `seq 1 5`; do uuidgen -r; done


fb8ce6f4-9e6f-4e32-8088-403720fd71a4

81ec8466-e4f0-47e9-b115-fad439b03363

83b90068-12bf-483a-995e-6938f8df380b

f4f1ba13-6f31-4c04-a168-eb3ac59b8f59

8b0b81ca-61f1-41df-867b-7cfe74f99d71

For more help,
 
# uuidgen -h


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

uuid
 
# apt-get install uuid

# uuid


99cde402-3fff-11e4-a7c6-50b7c3745b84
# uuid  -n 5


dfeeb2ba-4002-11e4-824d-50b7c3745b84

dfeeb6ca-4002-11e4-824e-50b7c3745b84

dfeeb80a-4002-11e4-824f-50b7c3745b84

dfeeb90e-4002-11e4-8250-50b7c3745b84

dfeeba80-4002-11e4-8251-50b7c3745b84

By normally generate the UUID random from the below path,
 
# cat /proc/sys/kernel/random/uuid


61a0d834-e8c1-4e73-acc7-255d5086e576

python:
 
# python  -c 'import uuid; print uuid.uuid1()'


49270506-3fff-11e4-b963-50b7c35a1e6e