UUIDD(8) System Administration UUIDD(8)
NAME
uuidd - UUID generation daemon
SYNOPSIS
uuidd [options]
DESCRIPTION
The uuidd daemon is used by the UUID library to generate universally
unique identifiers (UUIDs), especially time-based UUIDs, in a secure and
guaranteed-unique fashion, even in the face of large numbers of threads
running on different CPUs trying to grab UUIDs.
OPTIONS
-C, --cont-clock[=time]
Activate continuous clock handling for time based UUIDs. uuidd could
use all possible clock values, beginning with the daemon’s start
time. The optional argument can be used to set a value for the
max_clock_offset. This guarantees, that a clock value of a UUID will
always be within the range of the max_clock_offset.
The option -C or --cont-clock enables the feature with a default
max_clock_offset of 2 hours.
The option -C<NUM>[hd] or --cont-clock=<NUM>[hd] enables the feature
with a max_clock_offset of NUM seconds. In case of an appended h or
d, the NUM value is read in hours or days. The minimum value is 60
seconds, the maximum value is 365 days.
-d, --debug
Run uuidd in debugging mode. This prevents uuidd from running as a
daemon.
-F, --no-fork
Do not daemonize using a double-fork.
-k, --kill
If currently a uuidd daemon is running, kill it.
-n, --uuids number
When issuing a test request to a running uuidd, request a bulk
response of number UUIDs.
-P, --no-pid
Do not create a pid file.
-p, --pid path
Specify the pathname where the pid file should be written. By
default, the pid file is written to {runstatedir}/uuidd/uuidd.pid.
-q, --quiet
Suppress some failure messages.
-r, --random
Test uuidd by trying to connect to a running uuidd daemon and
request it to return a random-based UUID.
-S, --socket-activation
Do not create a socket but instead expect it to be provided by the
calling process. This implies --no-fork and --no-pid. This option is
intended to be used only with systemd(1). It needs to be enabled
with a configure option.
-s, --socket path
Make uuidd use this pathname for the unix-domain socket. By default,
the pathname used is {runstatedir}/uuidd/request. This option is
primarily for debugging purposes, since the pathname is hard-coded
in the libuuid library.
-T, --timeout number
Make uuidd exit after number seconds of inactivity.
-t, --time
Test uuidd by trying to connect to a running uuidd daemon and
request it to return a time-based UUID.
-h, --help
Display help text and exit.
-V, --version
Display version and exit.
EXAMPLE
Start up a daemon, print 42 random keys, and then stop the daemon:
uuidd -p /tmp/uuidd.pid -s /tmp/uuidd.socket
uuidd -d -r -n 42 -s /tmp/uuidd.socket
uuidd -d -k -s /tmp/uuidd.socket
AUTHOR
The uuidd daemon was written by Theodore Ts’o <tytso@mit.edu>.
SEE ALSO
uuid(3), uuidgen(1)
REPORTING BUGS
For bug reports, use the issue tracker
<https://github.com/util-linux/util-linux/issues>.
AVAILABILITY
The uuidd 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/>.
util-linux 2.41 2025-02-26 UUIDD(8)
Generated by dwww version 1.16 on Tue Dec 16 06:40:17 CET 2025.