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Create tag ${ searchTerm }
Create branch ${ searchTerm }
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${ noResults }
mergerfs/pages/documentation/runtime_interfaces/index.html

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RUNTIME INTERFACES
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RUNTIME INTERFACES
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file / directory xattrs
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SIGNALS
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IOCTLS
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<h1 id="runtime-interfaces">RUNTIME INTERFACES</h1>
<h2 id="runtime-config">RUNTIME CONFIG</h2>
<h4 id="mergerfs-pseudo-file">.mergerfs pseudo file</h4>
<pre><code>&lt;mountpoint&gt;/.mergerfs
</code></pre>
<p>There is a pseudo file available at the mount point which allows for
the runtime modification of certain <strong>mergerfs</strong> options. The file
will not show up in <strong>readdir</strong> but can be <strong>stat</strong>'ed and manipulated
via <a href="http://linux.die.net/man/2/listxattr">{list,get,set}xattrs</a>
calls.</p>
<p>Any changes made at runtime are <strong>not</strong> persisted. If you wish for
values to persist they must be included as options wherever you
configure the mounting of mergerfs (/etc/fstab).</p>
<h5 id="keys">Keys</h5>
<p>Use <code>getfattr -d /mountpoint/.mergerfs</code> or <code>xattr -l
/mountpoint/.mergerfs</code> to see all supported keys. Some are
informational and therefore read-only. <code>setxattr</code> will return EINVAL
(invalid argument) on read-only keys.</p>
<h5 id="values">Values</h5>
<p>Same as the command line.</p>
<h6 id="usermergerfsbranches">user.mergerfs.branches</h6>
<p>Used to query or modify the list of branches. When modifying there are
several shortcuts to easy manipulation of the list.</p>
<table>
<thead>
<tr>
<th>Value</th>
<th>Description</th>
</tr>
</thead>
<tbody>
<tr>
<td>[list]</td>
<td>set</td>
</tr>
<tr>
<td>+&lt;[list]</td>
<td>prepend</td>
</tr>
<tr>
<td>+&gt;[list]</td>
<td>append</td>
</tr>
<tr>
<td>-[list]</td>
<td>remove all values provided</td>
</tr>
<tr>
<td>-&lt;</td>
<td>remove first in list</td>
</tr>
<tr>
<td>-&gt;</td>
<td>remove last in list</td>
</tr>
</tbody>
</table>
<p><code>xattr -w user.mergerfs.branches +&lt;/mnt/drive3 /mnt/pool/.mergerfs</code></p>
<p>The <code>=NC</code>, <code>=RO</code>, <code>=RW</code> syntax works just as on the command line.</p>
<h5 id="example">Example</h5>
<pre><code>[trapexit:/mnt/mergerfs] $ getfattr -d .mergerfs
user.mergerfs.branches=&quot;/mnt/a=RW:/mnt/b=RW&quot;
user.mergerfs.minfreespace=&quot;4294967295&quot;
user.mergerfs.moveonenospc=&quot;false&quot;
...
[trapexit:/mnt/mergerfs] $ getfattr -n user.mergerfs.category.search .mergerfs
user.mergerfs.category.search=&quot;ff&quot;
[trapexit:/mnt/mergerfs] $ setfattr -n user.mergerfs.category.search -v newest .mergerfs
[trapexit:/mnt/mergerfs] $ getfattr -n user.mergerfs.category.search .mergerfs
user.mergerfs.category.search=&quot;newest&quot;
</code></pre>
<h4 id="file-directory-xattrs">file / directory xattrs</h4>
<p>While they won't show up when using <code>getfattr</code> <strong>mergerfs</strong> offers a
number of special xattrs to query information about the files
served. To access the values you will need to issue a
<a href="http://linux.die.net/man/2/getxattr">getxattr</a> for one of the
following:</p>
<ul>
<li><strong>user.mergerfs.basepath</strong>: the base mount point for the file given the current getattr policy</li>
<li><strong>user.mergerfs.relpath</strong>: the relative path of the file from the perspective of the mount point</li>
<li><strong>user.mergerfs.fullpath</strong>: the full path of the original file given the getattr policy</li>
<li><strong>user.mergerfs.allpaths</strong>: a NUL ('\0') separated list of full paths to all files found</li>
</ul>
<h2 id="signals">SIGNALS</h2>
<ul>
<li>USR1: This will cause mergerfs to send invalidation notifications to
the kernel for all files. This will cause all unused files to be
released from memory.</li>
<li>USR2: Trigger a general cleanup of currently unused memory. A more
thorough version of what happens every ~15 minutes.</li>
</ul>
<h2 id="ioctls">IOCTLS</h2>
<p>Found in <code>fuse_ioctl.cpp</code>:</p>
<pre><code class="language-C++">typedef char IOCTL_BUF[4096];
#define IOCTL_APP_TYPE 0xDF
#define IOCTL_FILE_INFO _IOWR(IOCTL_APP_TYPE,0,IOCTL_BUF)
#define IOCTL_GC _IO(IOCTL_APP_TYPE,1)
#define IOCTL_GC1 _IO(IOCTL_APP_TYPE,2)
#define IOCTL_INVALIDATE_ALL_NODES _IO(IOCTL_APP_TYPE,3)
</code></pre>
<ul>
<li>IOCTL_FILE_INFO: Same as the "file / directory xattrs" mentioned
above. Use a buffer size of 4096 bytes. Pass in a string of
"basepath", "relpath", "fullpath", or "allpaths". Receive details in
same buffer.</li>
<li>IOCTL_GC: Triggers a thorough garbage collection of excess
memory. Same as SIGUSR2.</li>
<li>IOCTL_GC1: Triggers a simple garbage collection of excess
memory. Same as what happens every 15 minutes normally.</li>
<li>IOCTL_INVALIDATE_ALL_NODES: Same as SIGUSR1. Send invalidation
notifications to the kernel for all files causing unused files to be
released from memory.</li>
</ul>
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