Manual: uuidgen

UUIDGEN(1)						User Commands						  UUIDGEN(1)

NAME
       uuidgen - create a new UUID value

SYNOPSIS
       uuidgen [options]

DESCRIPTION
       The uuidgen program creates (and prints) a new universally unique identifier (UUID) using the libuuid(3) library. The
       new UUID can reasonably be considered unique among all UUIDs created on the local system, and among UUIDs created on
       other systems in the past and in the future.

       There are three types of UUIDs which uuidgen can generate: time-based UUIDs, random-based UUIDs, and hash-based
       UUIDs. By default uuidgen will generate a random-based UUID if a high-quality random number generator is present.
       Otherwise, it will choose a time-based UUID. It is possible to force the generation of one of these first two UUID
       types by using the --random or --time options.

       The third type of UUID is generated with the --md5 or --sha1 options, followed by --namespace namespace and --name
       name. The namespace may either be a well-known UUID, or else an alias to one of the well-known UUIDs defined in RFC
       4122, that is @dns, @url, @oid, or @x500. The name is an arbitrary string value. The generated UUID is the digest of
       the concatenation of the namespace UUID and the name value, hashed with the MD5 or SHA1 algorithms. It is, therefore,
       a predictable value which may be useful when UUIDs are being used as handles or nonces for more complex values or
       values which shouldn’t be disclosed directly. See the RFC for more information.

OPTIONS
       -r, --random
	   Generate a random-based UUID. This method creates a UUID consisting mostly of random bits. It requires that the
	   operating system has a high quality random number generator, such as /dev/random.

       -t, --time
	   Generate a time-based UUID. This method creates a UUID based on the system clock plus the system’s ethernet
	   hardware address, if present.

       -m, --md5
	   Use MD5 as the hash algorithm.

       -s, --sha1
	   Use SHA1 as the hash algorithm.

       -6, --time-v6
	   Generate a time-based UUID. This method creates a UUID based on the system clock plus and is lexicographically
	   sortable according to the contained timestamp.

       -7, --time-v7
	   Generate a time-based UUID. This method creates a UUID based on the system clock plus and is lexicographically
	   sortable according to the contained timestamp.

       -n, --namespace namespace
	   Generate the hash with the namespace prefix. The namespace is UUID, or '@ns' where "ns" is well-known predefined
	   UUID addressed by namespace name (see above).

       -N, --name name
	   Generate the hash of the name.

       -C, --count num
	   Generate multiple UUIDs using the enhanced capability of the libuuid to cache time-based UUIDs, thus resulting in
	   improved performance. However, this holds no significance for other UUID types.

       -x, --hex
	   Interpret name name as a hexadecimal string.

       -h, --help
	   Display help text and exit.

       -V, --version
	   Display version and exit.

CONFORMING TO
       OSF DCE 1.1

EXAMPLES
       uuidgen --sha1 --namespace @dns --name "www.example.com"

AUTHORS
       uuidgen was written by Andreas Dilger for libuuid(3).

SEE ALSO
       uuidparse(1), libuuid(3), RFC 4122  RFC XXXX
       

REPORTING BUGS
       For bug reports, use the issue tracker .

AVAILABILITY
       The uuidgen command is part of the util-linux package which can be downloaded from Linux Kernel Archive
       .

util-linux 2.41.3					 2025-12-15						  UUIDGEN(1)