dbus-uuidgen
Utility to generate UUIDs
Synopsis
dbus-uuidgen
[--version] [--ensure[=FILENAME]]
[--get[=FILENAME]]
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examples
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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
bugs
Please send bug
reports to the D-Bus mailing list or bug tracker, see
http://www.freedesktop.org/software/dbus/
author
See
http://www.freedesktop.org/software/dbus/doc/AUTHORS