UUIDGEN(1) User Commands UUIDGEN(1)
uuidgen - create a new UUID value
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 Display version information 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. -x, --hex Interpret name name as a hexadecimal string.
OSF DCE 1.1
uuidgen --sha1 --namespace @dns --name "www.example.com"
uuidgen was written by Andreas Dilger for libuuid.
libuuid(3), RFC 4122
The uuidgen command is part of the util-linux package and is available from https://www.kernel.org/pub/linux/utils/util-linux/.
This page is part of the util-linux (a random collection of Linux utilities) project. Information about the project can be found at ⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a bug report for this manual page, send it to firstname.lastname@example.org. This page was obtained from the project's upstream Git repository ⟨git://git.kernel.org/pub/scm/utils/util-linux/util-linux.git⟩ on 2020-12-18. (At that time, the date of the most recent commit that was found in the repository was 2020-12-17.) If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up-to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to email@example.com util-linux June 2011 UUIDGEN(1)
Pages that refer to this page: uuidparse(1), uuid_generate(3), swaplabel(8), uuidd(8)