\subsection*{Autochanger Resource}
\index[sd]{Autochanger Resource }
\index[sd]{Resource!Autochanger }
\addcontentsline{toc}{subsection}{Autochanger Resource}

The Autochanger resource supports single or multiple drive
autochangers by grouping one or more Device resources     
into one unit called an autochanger in Bacula (often referred to
as a "tape library" by autochanger manufacturers).

\begin{description}
\item [Name = \lt{}Autochanger-Name\gt{}]
   \index[sd]{Name}
   Specifies the Name of the Autochanger. This name is used in
   the Director's Storage definition to refer to the autochanger.
   This directive is required.  

\item [Device = \lt{}Device-name1, device-name2, ...\gt{}]
   Specifies the names of the Device resource or
   resources that correspond
   to the autochanger drive.  If you have a multiple drive
   autochanger, you must specify multiple Device names, each
   one referring to a separate Device resource that contains a the
   Drive Index specification that corresponds to the drive
   number. You may specify multiple device names on
   a single line separated by commas, and/or you may specify
   multiple Device directives.
   This directive is required.  

\item [Changer Device = {\it name-string}]
   \index[sd]{Changer Device}
   The specified {\bf name-string} gives the system file name of the  autochanger
   device name. If specified in this resource, the Changer Device name
   is not needed in the Device resource. If it is specified in the Device
   resource (see above), it will take precedence over one specified in
   the Autochanger resource.

\item [Changer Command = {\it name-string}]
   \index[sd]{Changer Command  }
   The {\bf name-string} specifies an external program to be called  that will
   automatically change volumes as required by {\bf Bacula}.  Most frequently,
   you will specify the Bacula supplied {\bf mtx-changer}  script as follows.
   If it is specified here, it need not be specified in the Device
   resource. If it is specified in the Device resource, it will take
   precedence over the one specified in the Autochanger resource.

\end{description}

The following is an example of a valid Autochanger resource definition: 

\footnotesize
\begin{verbatim}
Autochanger {
  Name = "DDS-4-changer"
  Device = DDS-4-1, DDS-4-2, DDS-4-3
  Changer Device = /dev/sg0
  Changer Command = "/etc/bacula/mtx-changer %c %o %S %a %d"
}
Device {
  Name = "DDS-4-1"
  Drive Index = 0
  Autochanger = yes
  ...
}
Device {
  Name = "DDS-4-2"
  Drive Index = 1
  Autochanger = yes
  ...
Device {
  Name = "DDS-4-3"
  Drive Index = 2
  Autochanger = yes
  Autoselect = no
  ...
}
\end{verbatim}
\normalsize

Please note that it is important to include the {\bf Autochanger = yes} directive
in each Device definition that belongs to an Autochanger.  A device definition
should not belong to more than one Autochanger resource.  Also, your Device
directive in the Storage resource of the Director's conf file should have
the Autochanger's resource name rather than a name of one of the Devices.

If you have a drive that physically belongs to an Autochanger but you don't want
to have it automatically used when Bacula references the Autochanger for backups,
for example, you want to reserve it for restores, you can add the directive:

\footnotesize
\begin{verbatim}
Autoselect = no
\end{verbatim}
\normalsize

to the Device resource for that drive. In that case, Bacula will not automatically
select that drive when accessing the Autochanger. You can, still use the drive
by referencing it by the Device name rather than the Autochanger name. An example
of such a definition is shown above for the Device DDS-4-3, which will not be
selected when the name DDS-4-changer is used in a Storage definition, but will
be used if DDS-4-3 is used.
