Change server_uuid in MySQL

I want to know if there is any way to update server_uuid; I am trying master-slave replication, and I need different server_uuid. FYI - I don't have server_uuid in my my.cnf file, and when I update it like this:

> SET GLOBAL server_uuid = '1';

I get the following error:

ERROR 1238 (HY000): Variable 'server_uuid' is a read only variable