# phpman > man > dbus-uuidgen(1)

[DBUS-UUIDGEN(1)](https://www.chedong.com/phpMan.php/man/DBUS-UUIDGEN/1/markdown)                             User Commands                            [DBUS-UUIDGEN(1)](https://www.chedong.com/phpMan.php/man/DBUS-UUIDGEN/1/markdown)



## NAME
       dbus-uuidgen - Utility to generate UUIDs

## SYNOPSIS
       **dbus-uuidgen** [--version] [--ensure [_=FILENAME_]] [--get [_=FILENAME_]]


## DESCRIPTION
       The **dbus-uuidgen** command generates or reads a universally unique ID.

       Note that the D-Bus UUID has no relationship to RFC 4122 and does not generate UUIDs
       compatible with that spec. Many systems have a separate command for that (often called
       "uuidgen").

       See **<http://www.freedesktop.org/software/dbus/>** for more information about D-Bus.

       The primary usage of **dbus-uuidgen** is to run in the post-install script of a D-Bus package
       like this:

             dbus-uuidgen --ensure

       This will ensure that /var/lib/dbus/machine-id exists and has the uuid in it. It won't
       overwrite an existing uuid, since this id should remain fixed for a single machine until the
       next reboot at least.

       The important properties of the machine UUID are that 1) it remains unchanged until the next
       reboot and 2) it is different for any two running instances of the OS kernel. That is, if two
       processes see the same UUID, they should also see the same shared memory, UNIX domain
       sockets, local X displays, localhost.localdomain resolution, process IDs, and so forth.

       If you run **dbus-uuidgen** with no options it just prints a new uuid made up out of thin air.

       If you run it with --get, it prints the machine UUID by default, or the UUID in the specified
       file if you specify a file.

       If you try to change an existing machine-id on a running system, it will probably result in
       bad things happening. Don't try to change this file. Also, don't make it the same on two
       different systems; it needs to be different anytime there are two different kernels running.

       The UUID should be different on two different virtual machines, because there are two
       different kernels.

## OPTIONS
       The following options are supported:

### --get[=FILENAME]
           If a filename is not given, defaults to localstatedir/lib/dbus/machine-id (localstatedir
           is usually /var). If this file exists and is valid, the uuid in the file is printed on
           stdout. Otherwise, the command exits with a nonzero status.

### --ensure[=FILENAME]
           If a filename is not given, defaults to localstatedir/lib/dbus/machine-id (localstatedir
           is usually /var). If this file exists then it will be validated, and a failure code
           returned if it contains the wrong thing. If the file does not exist, it will be created
           with a new uuid in it. On success, prints no output.

### --version
           Print the version of dbus-uuidgen

## AUTHOR
       See **<http://www.freedesktop.org/software/dbus/doc/AUTHORS>**

## BUGS
       Please send bug reports to the D-Bus mailing list or bug tracker, see
### <http://www.freedesktop.org/software/dbus/>



D-Bus 1.12.20                                                                        [DBUS-UUIDGEN(1)](https://www.chedong.com/phpMan.php/man/DBUS-UUIDGEN/1/markdown)