UUID (Universally Unique IDentifier) is a unique set of character string that is guaranteed to be unique(well mostly). The above UUID is generated using version $ver of the uuid spec. Click here for UUID generated based on version 1 , version 2 , version 3 , version 4 , version 5 of the UUID specification. For v3 and v5 namespace parameter nstype ( one of dns/url/x500/nil ) and text ( an identifier in the given namespace ) is required.