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,
−−randomGenerate a random-based UUID. This method creates a
UUID consisting mostly of random bits. It requires that
the operating system have a high quality random number
generator, such as /dev/random.
−t,
−−timeGenerate a time-based UUID. This method creates a UUID based on the system clock plus the system's ethernet hardware address, if present.
−h,
−−helpDisplay help text and exit.
−V,
−−versionDisplay version information and exit.
−m,
−−md5Use MD5 as the hash algorithm.
−s,
−−sha1Use SHA1 as the hash algorithm.
−n,
−−namespace namespaceGenerate 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 nameGenerate the hash of the name.
−x,
−−hexInterpret name name as a hexadecimal string.