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<span class="md-nav__icon md-icon"></span> </label> <nav class="md-nav" data-md-level="1" aria-labelledby="__nav_4_label" aria-expanded="false"> <label class="md-nav__title" for="__nav_4"> <span class="md-nav__icon md-icon"></span> Config </label> <ul class="md-nav__list" data-md-scrollfix> <li class="md-nav__item"> <a href="../config/terminology/" class="md-nav__link"> <span class="md-ellipsis"> Terminology </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/options/" class="md-nav__link"> <span class="md-ellipsis"> Options </span>
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<li class="md-nav__item"> <a href="../config/deprecated_options/" class="md-nav__link"> <span class="md-ellipsis"> Deprecated Options </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/branches/" class="md-nav__link"> <span class="md-ellipsis"> branches </span>
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<li class="md-nav__item"> <a href="../config/functions_categories_and_policies/" class="md-nav__link"> <span class="md-ellipsis"> functions, categories and policies </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/func_readdir/" class="md-nav__link"> <span class="md-ellipsis"> func.readdir </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/rename_and_link/" class="md-nav__link"> <span class="md-ellipsis"> rename and link </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/cache/" class="md-nav__link"> <span class="md-ellipsis"> caching </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/readahead/" class="md-nav__link"> <span class="md-ellipsis"> readahead </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/inodecalc/" class="md-nav__link"> <span class="md-ellipsis"> inodecalc </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/threads/" class="md-nav__link"> <span class="md-ellipsis"> threads </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/pin-threads/" class="md-nav__link"> <span class="md-ellipsis"> pin-threads </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/link_cow/" class="md-nav__link"> <span class="md-ellipsis"> link_cow </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/fuse_msg_size/" class="md-nav__link"> <span class="md-ellipsis"> fuse_msg_size </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/follow-symlinks/" class="md-nav__link"> <span class="md-ellipsis"> follow-symlinks </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/link-exdev/" class="md-nav__link"> <span class="md-ellipsis"> link-exdev </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/rename-exdev/" class="md-nav__link"> <span class="md-ellipsis"> rename-exdev </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/symlinkify/" class="md-nav__link"> <span class="md-ellipsis"> symlinkify </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/nullrw/" class="md-nav__link"> <span class="md-ellipsis"> nullrw </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/xattr/" class="md-nav__link"> <span class="md-ellipsis"> xattr </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/nfsopenhack/" class="md-nav__link"> <span class="md-ellipsis"> nfsopenhack </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/statfs/" class="md-nav__link"> <span class="md-ellipsis"> statfs / statvfs </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/flush-on-close/" class="md-nav__link"> <span class="md-ellipsis"> flush-on-close </span>
</a> </li>
<li class="md-nav__item"> <a href="../config/export-support/" class="md-nav__link"> <span class="md-ellipsis"> export-support </span>
</a> </li>
</ul> </nav> </li>
<li class="md-nav__item"> <a href="../error_handling/" class="md-nav__link"> <span class="md-ellipsis"> Error Handling </span>
</a> </li>
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<span class="md-nav__icon md-icon"></span> </label> <a href="./" class="md-nav__link md-nav__link--active"> <span class="md-ellipsis"> Runtime Interfaces </span>
</a>
<nav class="md-nav md-nav--secondary" aria-label="Table of contents"> <label class="md-nav__title" for="__toc"> <span class="md-nav__icon md-icon"></span> Table of contents </label> <ul class="md-nav__list" data-md-component="toc" data-md-scrollfix> <li class="md-nav__item"> <a href="#runtime-config" class="md-nav__link"> <span class="md-ellipsis"> Runtime Config </span> </a> <nav class="md-nav" aria-label="Runtime Config"> <ul class="md-nav__list"> <li class="md-nav__item"> <a href="#mergerfs-pseudo-file" class="md-nav__link"> <span class="md-ellipsis"> .mergerfs pseudo file </span> </a> <nav class="md-nav" aria-label=".mergerfs pseudo file"> <ul class="md-nav__list"> <li class="md-nav__item"> <a href="#keys" class="md-nav__link"> <span class="md-ellipsis"> Keys </span> </a> </li> <li class="md-nav__item"> <a href="#values" class="md-nav__link"> <span class="md-ellipsis"> Values </span> </a> <nav class="md-nav" aria-label="Values"> <ul class="md-nav__list"> <li class="md-nav__item"> <a href="#usermergerfsbranches" class="md-nav__link"> <span class="md-ellipsis"> user.mergerfs.branches </span> </a> </li> <li class="md-nav__item"> <a href="#example" class="md-nav__link"> <span class="md-ellipsis"> Example </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class="md-nav__item"> <a href="#file-directory-xattrs" class="md-nav__link"> <span class="md-ellipsis"> file / directory xattrs </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item"> <a href="#signals" class="md-nav__link"> <span class="md-ellipsis"> Signals </span> </a> </li> <li class="md-nav__item"> <a href="#ioctl" class="md-nav__link"> <span class="md-ellipsis"> ioctl </span> </a> </li> </ul> </nav> </li>
<li class="md-nav__item"> <a href="../remote_filesystems/" class="md-nav__link"> <span class="md-ellipsis"> Remote Filesystems </span>
</a> </li>
<li class="md-nav__item"> <a href="../tips_notes/" class="md-nav__link"> <span class="md-ellipsis"> Tips and Notes </span>
</a> </li>
<li class="md-nav__item"> <a href="../known_issues_bugs/" class="md-nav__link"> <span class="md-ellipsis"> Known Issues and Bugs </span>
</a> </li>
<li class="md-nav__item"> <a href="../project_comparisons/" class="md-nav__link"> <span class="md-ellipsis"> Project Comparisons </span>
</a> </li>
<li class="md-nav__item"> <a href="../performance/" class="md-nav__link"> <span class="md-ellipsis"> Tweaking Performance </span>
</a> </li>
<li class="md-nav__item"> <a href="../benchmarking/" class="md-nav__link"> <span class="md-ellipsis"> Benchmarking </span>
</a> </li>
<li class="md-nav__item"> <a href="../tooling/" class="md-nav__link"> <span class="md-ellipsis"> Tooling </span>
</a> </li>
<li class="md-nav__item md-nav__item--nested"> <input class="md-nav__toggle md-toggle " type="checkbox" id="__nav_14" > <label class="md-nav__link" for="__nav_14" id="__nav_14_label" tabindex="0"> <span class="md-ellipsis"> FAQ </span>
<span class="md-nav__icon md-icon"></span> </label> <nav class="md-nav" data-md-level="1" aria-labelledby="__nav_14_label" aria-expanded="false"> <label class="md-nav__title" for="__nav_14"> <span class="md-nav__icon md-icon"></span> FAQ </label> <ul class="md-nav__list" data-md-scrollfix> <li class="md-nav__item"> <a href="../faq/reliability_and_scalability/" class="md-nav__link"> <span class="md-ellipsis"> Reliability and Scalability </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/usage_and_functionality/" class="md-nav__link"> <span class="md-ellipsis"> Usage and Functionality </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/configuration_and_policies/" class="md-nav__link"> <span class="md-ellipsis"> Configuration and Policies </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/compatibility_and_integration/" class="md-nav__link"> <span class="md-ellipsis"> Compatibility and Integration </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/recommendations_and_warnings/" class="md-nav__link"> <span class="md-ellipsis"> Recommendations and Warnings </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/technical_behavior_and_limitations/" class="md-nav__link"> <span class="md-ellipsis"> Technical Behavior and Limitations </span>
</a> </li>
<li class="md-nav__item"> <a href="../faq/limit_drive_spinup/" class="md-nav__link"> <span class="md-ellipsis"> Limiting drive spinup </span>
</a> </li>
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<nav class="md-nav md-nav--secondary" aria-label="Table of contents"> <label class="md-nav__title" for="__toc"> <span class="md-nav__icon md-icon"></span> Table of contents </label> <ul class="md-nav__list" data-md-component="toc" data-md-scrollfix> <li class="md-nav__item"> <a href="#runtime-config" class="md-nav__link"> <span class="md-ellipsis"> Runtime Config </span> </a> <nav class="md-nav" aria-label="Runtime Config"> <ul class="md-nav__list"> <li class="md-nav__item"> <a href="#mergerfs-pseudo-file" class="md-nav__link"> <span class="md-ellipsis"> .mergerfs pseudo file </span> </a> <nav class="md-nav" aria-label=".mergerfs pseudo file"> <ul class="md-nav__list"> <li class="md-nav__item"> <a href="#keys" class="md-nav__link"> <span class="md-ellipsis"> Keys </span> </a> </li> <li class="md-nav__item"> <a href="#values" class="md-nav__link"> <span class="md-ellipsis"> Values </span> </a> <nav class="md-nav" aria-label="Values"> <ul class="md-nav__list"> <li class="md-nav__item"> <a href="#usermergerfsbranches" class="md-nav__link"> <span class="md-ellipsis"> user.mergerfs.branches </span> </a> </li> <li class="md-nav__item"> <a href="#example" class="md-nav__link"> <span class="md-ellipsis"> Example </span> </a> </li> </ul> </nav> </li> </ul> </nav> </li> <li class="md-nav__item"> <a href="#file-directory-xattrs" class="md-nav__link"> <span class="md-ellipsis"> file / directory xattrs </span> </a> </li> </ul> </nav> </li> <li class="md-nav__item"> <a href="#signals" class="md-nav__link"> <span class="md-ellipsis"> Signals </span> </a> </li> <li class="md-nav__item"> <a href="#ioctl" class="md-nav__link"> <span class="md-ellipsis"> ioctl </span> </a> </li> </ul> </nav> </div> </div> </div> <div class="md-content" data-md-component="content"> <article class="md-content__inner md-typeset">
<a href="https://github.com/trapexit/mergerfs/tree/master/mkdocs/docs/runtime_interfaces.md" title="Edit this page" class="md-content__button md-icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M10 20H6V4h7v5h5v3.1l2-2V8l-6-6H6c-1.1 0-2 .9-2 2v16c0 1.1.9 2 2 2h4zm10.2-7c.1 0 .3.1.4.2l1.3 1.3c.2.2.2.6 0 .8l-1 1-2.1-2.1 1-1c.1-.1.2-.2.4-.2m0 3.9L14.1 23H12v-2.1l6.1-6.1z"/></svg> </a> <a href="https://github.com/trapexit/mergerfs/tree/master/mkdocs/docs/runtime_interfaces.md" title="View source of this page" class="md-content__button md-icon"> <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M17 18c.56 0 1 .44 1 1s-.44 1-1 1-1-.44-1-1 .44-1 1-1m0-3c-2.73 0-5.06 1.66-6 4 .94 2.34 3.27 4 6 4s5.06-1.66 6-4c-.94-2.34-3.27-4-6-4m0 6.5a2.5 2.5 0 0 1-2.5-2.5 2.5 2.5 0 0 1 2.5-2.5 2.5 2.5 0 0 1 2.5 2.5 2.5 2.5 0 0 1-2.5 2.5M9.27 20H6V4h7v5h5v4.07c.7.08 1.36.25 2 .49V8l-6-6H6a2 2 0 0 0-2 2v16a2 2 0 0 0 2 2h4.5a8.2 8.2 0 0 1-1.23-2"/></svg> </a>
<h1 id="runtime-interfaces">Runtime Interfaces</h1><h2 id="runtime-config">Runtime Config</h2><h3 id="mergerfs-pseudo-file">.mergerfs pseudo file</h3><div class="language-text highlight"><pre><span></span><code><span id="__span-0-1"><a id="__codelineno-0-1" name="__codelineno-0-1" href="#__codelineno-0-1"></a><mountpoint>/.mergerfs</span></code></pre></div><p>There is a pseudo file available at the mount point which allows forthe runtime modification of certain <strong>mergerfs</strong> options. The filewill not show up in <strong>readdir</strong> but can be <strong>stat</strong>'ed and manipulatedvia <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 forvalues to persist they must be included as options wherever youconfigure the mounting of mergerfs (/etc/fstab).</p><h4 id="keys">Keys</h4><p>Use <code>getfattr -d /mountpoint/.mergerfs</code> or <code>xattr -l/mountpoint/.mergerfs</code> to see all supported keys. Some areinformational and therefore read-only. <code>setxattr</code> will return EINVAL(invalid argument) on read-only keys.</p><h4 id="values">Values</h4><p>Same as the command line.</p><h5 id="usermergerfsbranches">user.mergerfs.branches</h5><p>Used to query or modify the list of branches. When modifying there areseveral 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>+<[list]</td><td>prepend</td></tr><tr><td>+>[list]</td><td>append</td></tr><tr><td>-[list]</td><td>remove all values provided</td></tr><tr><td>-<</td><td>remove first in list</td></tr><tr><td>-></td><td>remove last in list</td></tr></tbody></table><p><code>xattr -w user.mergerfs.branches +</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><div class="language-text highlight"><pre><span></span><code><span id="__span-1-1"><a id="__codelineno-1-1" name="__codelineno-1-1" href="#__codelineno-1-1"></a>[trapexit:/mnt/mergerfs] $ getfattr -d .mergerfs</span><span id="__span-1-2"><a id="__codelineno-1-2" name="__codelineno-1-2" href="#__codelineno-1-2"></a>user.mergerfs.branches="/mnt/a=RW:/mnt/b=RW"</span><span id="__span-1-3"><a id="__codelineno-1-3" name="__codelineno-1-3" href="#__codelineno-1-3"></a>user.mergerfs.minfreespace="4294967295"</span><span id="__span-1-4"><a id="__codelineno-1-4" name="__codelineno-1-4" href="#__codelineno-1-4"></a>user.mergerfs.moveonenospc="false"</span><span id="__span-1-5"><a id="__codelineno-1-5" name="__codelineno-1-5" href="#__codelineno-1-5"></a>...</span><span id="__span-1-6"><a id="__codelineno-1-6" name="__codelineno-1-6" href="#__codelineno-1-6"></a></span><span id="__span-1-7"><a id="__codelineno-1-7" name="__codelineno-1-7" href="#__codelineno-1-7"></a>[trapexit:/mnt/mergerfs] $ getfattr -n user.mergerfs.category.search .mergerfs</span><span id="__span-1-8"><a id="__codelineno-1-8" name="__codelineno-1-8" href="#__codelineno-1-8"></a>user.mergerfs.category.search="ff"</span><span id="__span-1-9"><a id="__codelineno-1-9" name="__codelineno-1-9" href="#__codelineno-1-9"></a></span><span id="__span-1-10"><a id="__codelineno-1-10" name="__codelineno-1-10" href="#__codelineno-1-10"></a>[trapexit:/mnt/mergerfs] $ setfattr -n user.mergerfs.category.search -v newest .mergerfs</span><span id="__span-1-11"><a id="__codelineno-1-11" name="__codelineno-1-11" href="#__codelineno-1-11"></a>[trapexit:/mnt/mergerfs] $ getfattr -n user.mergerfs.category.search .mergerfs</span><span id="__span-1-12"><a id="__codelineno-1-12" name="__codelineno-1-12" href="#__codelineno-1-12"></a>user.mergerfs.category.search="newest"</span></code></pre></div><h3 id="file-directory-xattrs">file / directory xattrs</h3><p>While they won't show up when using <code>getfattr</code> <strong>mergerfs</strong> offers anumber of special xattrs to query information about the filesserved. To access the values you will need to issue a<a href="http://linux.die.net/man/2/getxattr">getxattr</a> for one of thefollowing:</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="ioctl">ioctl</h2><p>Found in <code>fuse_ioctl.cpp</code>:</p><div class="language-C++ highlight"><pre><span></span><code><span id="__span-2-1"><a id="__codelineno-2-1" name="__codelineno-2-1" href="#__codelineno-2-1"></a><span class="k">typedef</span><span class="w"> </span><span class="kt">char</span><span class="w"> </span><span class="n">IOCTL_BUF</span><span class="p">[</span><span class="mi">4096</span><span class="p">];</span></span><span id="__span-2-2"><a id="__codelineno-2-2" name="__codelineno-2-2" href="#__codelineno-2-2"></a><span class="cp">#define IOCTL_APP_TYPE 0xDF</span></span><span id="__span-2-3"><a id="__codelineno-2-3" name="__codelineno-2-3" href="#__codelineno-2-3"></a><span class="cp">#define IOCTL_FILE_INFO _IOWR(IOCTL_APP_TYPE,0,IOCTL_BUF)</span></span><span id="__span-2-4"><a id="__codelineno-2-4" name="__codelineno-2-4" href="#__codelineno-2-4"></a><span class="cp">#define IOCTL_GC _IO(IOCTL_APP_TYPE,1)</span></span><span id="__span-2-5"><a id="__codelineno-2-5" name="__codelineno-2-5" href="#__codelineno-2-5"></a><span class="cp">#define IOCTL_GC1 _IO(IOCTL_APP_TYPE,2)</span></span><span id="__span-2-6"><a id="__codelineno-2-6" name="__codelineno-2-6" href="#__codelineno-2-6"></a><span class="cp">#define IOCTL_INVALIDATE_ALL_NODES _IO(IOCTL_APP_TYPE,3)</span></span></code></pre></div><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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