UUIDGEN(1) User Commands UUIDGEN(1)

uuidgen - create a new UUID value

uuidgen [options]

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.

-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.

-h, --help

Display help text and exit.

-V, --version

Print version and exit.

-m, --md5

Use MD5 as the hash algorithm.

-s, --sha1

Use SHA1 as the hash algorithm.

-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.


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

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

uuidparse(1), libuuid(3), RFC 4122 https://tools.ietf.org/html/rfc4122

For bug reports, use the issue tracker at https://github.com/util-linux/util-linux/issues.

The uuidgen command is part of the util-linux package which can be downloaded from Linux Kernel Archive https://www.kernel.org/pub/linux/utils/util-linux/.

2024-05-06 util-linux 2.40.1