dbus-uuidgen Man page

DBUS-UUIDGEN(1) User Commands DBUS-UUIDGEN(1)

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 1.10.6 DBUS-UUIDGEN(1)