---
name: "uuidd"
section: "8"
platform: "linux"
package: "util-linux"
version: "2.42.4-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/uuidd"
---

# uuidd(8)

UUID generation daemon

## 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)](/systemd/1.md). 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)](/uuid/3.md), [**uuidgen**(1)](/uuidgen/1.md)

## 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/\>.