1dbus-uuidgen(1)             General Commands Manual            dbus-uuidgen(1)
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NAME

6       dbus-uuidgen - Utility to generate UUIDs
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SYNOPSIS

9       dbus-uuidgen [--version] [--ensure[=FILENAME]] [--get[=FILENAME]]
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DESCRIPTION

13       The dbus-uuidgen command generates or reads a universally unique ID.
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16       Note  that  the D-Bus UUID has no relationship to RFC 4122 and does not
17       generate UUIDs compatible with that spec. Many systems have a  separate
18       command for that (often called "uuidgen").
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21       See   http://www.freedesktop.org/software/dbus/  for  more  information
22       about D-Bus.
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25       The primary usage of dbus-uuidgen is to run in the post-install  script
26       of a D-Bus package like this:
27         dbus-uuidgen --ensure
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30       This  will ensure that /var/lib/dbus/machine-id exists and has the uuid
31       in it.  It won't overwrite an  existing  uuid,  since  this  id  should
32       remain fixed for a single machine until the next reboot at least.
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35       The  important  properties  of  the machine UUID are that 1) it remains
36       unchanged until the next reboot and 2) it is different for any two run‐
37       ning instances of the OS kernel. That is, if two processes see the same
38       UUID, they should also see the same shared memory, UNIX domain sockets,
39       local X displays, localhost.localdomain resolution, process IDs, and so
40       forth.
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43       If you run dbus-uuidgen with no options it just prints a new uuid  made
44       up out of thin air.
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47       If you run it with --get, it prints the machine UUID by default, or the
48       UUID in the specified file if you specify a file.
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51       If you try to change an existing machine-id on  a  running  system,  it
52       will  probably result in bad things happening. Don't try to change this
53       file. Also, don't make it the same on two different systems;  it  needs
54       to be different anytime there are two different kernels running.
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57       The UUID should be different on two different virtual machines, because
58       there are two different kernels.
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OPTIONS

62       The following options are supported:
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64       --get[=FILENAME]
65              If  a  filename  is   not   given,   defaults   to   localstate‐
66              dir/lib/dbus/machine-id (localstatedir is usually /var). If this
67              file exists and is valid, the uuid in the  file  is  printed  on
68              stdout. Otherwise, the command exits with a nonzero status.
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71       --ensure[=FILENAME]
72              If   a   filename   is   not   given,  defaults  to  localstate‐
73              dir/lib/dbus/machine-id (localstatedir is usually /var). If this
74              file  exists  then  it  will  be  validated,  and a failure code
75              returned if it contains the wrong thing.  If the file  does  not
76              exist,  it  will  be created with a new uuid in it.  On success,
77              prints no output.
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80       --version
81              Print the version of dbus-uuidgen
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AUTHOR

85       See http://www.freedesktop.org/software/dbus/doc/AUTHORS
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BUGS

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