uuidd — UUID generation daemon


uuidd [options]


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.


−d, −−debug

Run uuidd in debugging mode. This prevents uuidd from running as a daemon.

−h, −−help

Display help screen and exit.

−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, −−pid path

Specify the pathname where the pid file should be written. By default, the pid file is written to /run/uuidd/

−P, −−no−pid

Do not create pid file.

−F, −−no−fork

Do not daemonize using double-fork.

−S, −−socket−activation

Do not create the socket and instead expect it to be provided by the calling process. Implies --no-fork and --no-pid. As of this writing, this option is supposed to be used only with systemd. This option must be enabled with a configure option.

−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 path

Specify the pathname used for the unix-domain socket used by uuidd. By default, the pathname used is /run/uuidd/request. This is primarily for debugging purposes, since the pathname is hard-coded in the libuuid library.

−T, −−timeout timeout

Specify a timeout for uuidd. If specified, then uuidd will exit after timeout 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.

−V, −−version

Output version information and exit.


Start up a daemon, print 42 random keys, and then stop the daemon.

uuidd -p /tmp/ -s /tmp/uuidd.socket
uuidd -d -r -n 42 -s /tmp/uuidd.socket
uuidd -d -k -s /tmp/uuidd.socket


The uuidd daemon was written by Theodore Ts'o <>.


The uuidd daemon is part of the util-linux package and is available from


uuid(3), uuidgen(1)

  Copyright 2007 by Theodore Ts'o.  All Rights Reserved.
This file may be copied under the terms of the GNU Public License.