Section: User Commands (1)
Updated: June 2011
uuidgen - create a new UUID value
program creates (and prints)
a new universally unique identifier (UUID) using the
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
can generate: time-based UUIDs, random-based UUIDs, and hash-based UUIDs.
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
The third type of UUID is generated with the
options, followed by
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
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 have a high
quality random number generator, such as
- -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
- -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
was written by Andreas Dilger for libuuid.
The uuidgen command is part of the util-linux package and is available from