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<h2>
<b><font face="ARIAL NARROW,HELVETICA">The Data Management API (DMAPI)</font></b></h2>

<p>
The Data Management API (DMAPI) is the mechanism within
the XFS filesystem for passing file management
requests between the kernel and a hierarchical
storage management system (HSM).
</p>

<p>
In order to configure an HSM, you must ensure that
you have installed DMAPI and the appropriate patches.
</p>

<p>
This page provides information on the following topics:
<br>
<br>
<li>
<A HREF="#_dmapistatus">DMAPI status in XFS</A>
</li>
<li>
<A HREF="#_dmapibuild">Building DMAPI</A>
</li>
<li>
<A HREF="#_dmapidev">The DMAPI device</A>
</li>
<li>
<A HREF="#_dmapilib">The DMAPI libraries</A>
</li>
<li>
<A HREF="#_mountdmapi">Mounting filesystems for use with DMAPI</A>
</li>
</p>


<h3>
<A NAME="_dmapistatus">DMAPI Status in XFS</A>
</h3>

<p>
The current status of the individual DMAPI functions in XFS can
be found in the file <tt>linux/fs/xfs/dmapi/Status</tt>.
</p>


<h3>
<A NAME="_dmapibuild">Building DMAPI</A>
</h3>

<p>
To build DMAPI, set the DMAPI config flag when you
configure XFS as part of your build.  This
flag is in the collection of XFS configuration options.
</p>


<h3>
<A NAME="_dmapidev">The DMAPI Device</A>
</h3>

<p>
In order to use DMAPI, you need to create the device <tt>/dev/dmapi</tt>;
this is the interface the user library uses to communicate with the
kernel side of DMAPI.
</p>

<p>
Execute the following command to create the DMAPI device:
</p>


<ul>
<tt>mknod /dev/dmapi c 10 140</tt>
</ul>


<h3>
<A NAME="_dmapilib">The DMAPI Libraries</A>
</h3>

<p>
The user library for DMAPI is <tt>cmd/xfs/libdm/libdm.so</tt>.
The user library requires the handle
library <tt>cmd/xfs/handle/libhandle.a</tt>.  The tests in
<tt>cmd/xfs/libdm</tt> link with these libraries.
</p>


<h3>
<A NAME="_mountdmapi">Mounting Filesystems for use with DMAPI</A>
</h3>

<p>
In order for filesystems to be managed by an HSF,
they must be mounted to enable the DMAPI interface.
To mount a filesystem for use with DMAPI, use the following
command:
</p>

<ul>
<tt>mount -o dmapi /dev/<i>fs-dev</i> /mntpt</tt>
</ul>

<br>
<br>


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