# uuidd

## 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**[**=**_number_[**hd**]]
               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 'max_clock_offset'. This guarantees that a clock
               value of a UUID will always be within the range of
               'max_clock_offset'.
    
               The option **-C** or **--cont-clock**(without an argument) enables
               the feature with a default 'max_clock_offset' of 2 hours.
    
               The option **-C** _number_ or **--cont-clock=**_number_ enables the feature
               with a 'max_clock_offset' of _number_ seconds. In case of an
               appended **h** or **d** , _number_ is understood 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
    


## 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/>. 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
           util-linux@vger.kernel.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
           2025-08-11. (At that time, the date of the most recent commit that
           was found in the repository was 2025-08-05.) 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 man-pages@man7.org
    
    util-linux 2.42-start-521-ec46  2025-08-09                       _UUIDD_(8)
    


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