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<!DOCTYPE html> <!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]--> <!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]--> <head> <meta charset="utf-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>QEMU persistent reservation helper — QEMU qemu-kvm-6.2.0-53.module+el8.10.0+2055+8eb7870b.4 documentation</title> <link rel="shortcut icon" href="../_static/qemu_32x32.png"/> <link rel="stylesheet" href="../_static/css/theme.css" type="text/css" /> <link rel="stylesheet" href="../_static/pygments.css" type="text/css" /> <link rel="index" title="Index" href="../genindex.html" /> <link rel="search" title="Search" href="../search.html" /> <link rel="next" title="QEMU SystemTap trace tool" href="qemu-trace-stap.html" /> <link rel="prev" title="QEMU Disk Network Block Device Server" href="qemu-nbd.html" /> <script src="../_static/js/modernizr.min.js"></script> </head> <body class="wy-body-for-nav"> <div class="wy-grid-for-nav"> <nav 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class="rst-content"> <div role="navigation" aria-label="breadcrumbs navigation"> <ul class="wy-breadcrumbs"> <li><a href="../index.html">Docs</a> »</li> <li><a href="index.html">Tools</a> »</li> <li>QEMU persistent reservation helper</li> <li class="wy-breadcrumbs-aside"> <a href="https://gitlab.com/qemu-project/qemu/blob/master/docs/tools/qemu-pr-helper.rst" class="fa fa-gitlab"> Edit on GitLab</a> </li> </ul> <hr/> </div> <div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article"> <div itemprop="articleBody"> <div class="section" id="qemu-persistent-reservation-helper"> <h1>QEMU persistent reservation helper<a class="headerlink" href="#qemu-persistent-reservation-helper" title="Permalink to this headline">¶</a></h1> <div class="section" id="synopsis"> <h2>Synopsis<a class="headerlink" href="#synopsis" title="Permalink to this headline">¶</a></h2> <p><strong>qemu-pr-helper</strong> [<em>OPTION</em>]</p> </div> <div class="section" id="description"> <h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2> <p>Implements the persistent reservation helper for QEMU.</p> <p>SCSI persistent reservations allow restricting access to block devices to specific initiators in a shared storage setup. When implementing clustering of virtual machines, it is a common requirement for virtual machines to send persistent reservation SCSI commands. However, the operating system restricts sending these commands to unprivileged programs because incorrect usage can disrupt regular operation of the storage fabric. QEMU’s SCSI passthrough devices <code class="docutils literal notranslate"><span class="pre">scsi-block</span></code> and <code class="docutils literal notranslate"><span class="pre">scsi-generic</span></code> support passing guest persistent reservation requests to a privileged external helper program. <strong class="program">qemu-pr-helper</strong> is that external helper; it creates a socket which QEMU can connect to to communicate with it.</p> <p>If you want to run VMs in a setup like this, this helper should be started as a system service, and you should read the QEMU manual section on “persistent reservation managers” to find out how to configure QEMU to connect to the socket created by <strong class="program">qemu-pr-helper</strong>.</p> <p>After connecting to the socket, <strong class="program">qemu-pr-helper</strong> can optionally drop root privileges, except for those capabilities that are needed for its operation.</p> <p><strong class="program">qemu-pr-helper</strong> can also use the systemd socket activation protocol. In this case, the systemd socket unit should specify a Unix stream socket, like this:</p> <div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="p">[</span><span class="n">Socket</span><span class="p">]</span> <span class="n">ListenStream</span><span class="o">=/</span><span class="n">var</span><span class="o">/</span><span class="n">run</span><span class="o">/</span><span class="n">qemu</span><span class="o">-</span><span class="n">pr</span><span class="o">-</span><span class="n">helper</span><span class="o">.</span><span class="n">sock</span> </pre></div> </div> </div> <div class="section" id="options"> <h2>Options<a class="headerlink" href="#options" title="Permalink to this headline">¶</a></h2> <dl class="option"> <dt id="cmdoption-qemu-pr-helper-d"> <code class="descname">-d</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--daemon</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-qemu-pr-helper-d" title="Permalink to this definition">¶</a></dt> <dd><p>run in the background (and create a PID file)</p> </dd></dl> <dl class="option"> <dt id="cmdoption-qemu-pr-helper-q"> <code class="descname">-q</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--quiet</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-qemu-pr-helper-q" title="Permalink to this definition">¶</a></dt> <dd><p>decrease verbosity</p> </dd></dl> <dl class="option"> <dt id="cmdoption-qemu-pr-helper-v"> <code class="descname">-v</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--verbose</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-qemu-pr-helper-v" title="Permalink to this definition">¶</a></dt> <dd><p>increase verbosity</p> </dd></dl> <dl class="option"> <dt id="cmdoption-qemu-pr-helper-f"> <code class="descname">-f</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--pidfile</code><code class="descclassname">=PATH</code><a class="headerlink" href="#cmdoption-qemu-pr-helper-f" title="Permalink to this definition">¶</a></dt> <dd><p>PID file when running as a daemon. By default the PID file is created in the system runtime state directory, for example <code class="file docutils literal notranslate"><span class="pre">/var/run/qemu-pr-helper.pid</span></code>.</p> </dd></dl> <dl class="option"> <dt id="cmdoption-qemu-pr-helper-k"> <code class="descname">-k</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--socket</code><code class="descclassname">=PATH</code><a class="headerlink" href="#cmdoption-qemu-pr-helper-k" title="Permalink to this definition">¶</a></dt> <dd><p>path to the socket. By default the socket is created in the system runtime state directory, for example <code class="file docutils literal notranslate"><span class="pre">/var/run/qemu-pr-helper.sock</span></code>.</p> </dd></dl> <dl class="option"> <dt id="cmdoption-qemu-pr-helper-t"> <code class="descname">-T</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--trace</code><code class="descclassname"> [[enable=]PATTERN][,events=FILE][,file=FILE]</code><a class="headerlink" href="#cmdoption-qemu-pr-helper-t" title="Permalink to this definition">¶</a></dt> <dd><p>Specify tracing options.</p> <p><code class="docutils literal notranslate"><span class="pre">[enable=]PATTERN</span></code></p> <blockquote> <div><p>Immediately enable events matching <em>PATTERN</em> (either event name or a globbing pattern). This option is only available if QEMU has been compiled with the <code class="docutils literal notranslate"><span class="pre">simple</span></code>, <code class="docutils literal notranslate"><span class="pre">log</span></code> or <code class="docutils literal notranslate"><span class="pre">ftrace</span></code> tracing backend. To specify multiple events or patterns, specify the <code class="xref std std-option docutils literal notranslate"><span class="pre">-trace</span></code> option multiple times.</p> <p>Use <code class="xref std std-option docutils literal notranslate"><span class="pre">-trace</span> <span class="pre">help</span></code> to print a list of names of trace points.</p> </div></blockquote> <p><code class="docutils literal notranslate"><span class="pre">events=FILE</span></code></p> <blockquote> <div>Immediately enable events listed in <em>FILE</em>. The file must contain one event name (as listed in the <code class="docutils literal notranslate"><span class="pre">trace-events-all</span></code> file) per line; globbing patterns are accepted too. This option is only available if QEMU has been compiled with the <code class="docutils literal notranslate"><span class="pre">simple</span></code>, <code class="docutils literal notranslate"><span class="pre">log</span></code> or <code class="docutils literal notranslate"><span class="pre">ftrace</span></code> tracing backend.</div></blockquote> <p><code class="docutils literal notranslate"><span class="pre">file=FILE</span></code></p> <blockquote> <div>Log output traces to <em>FILE</em>. This option is only available if QEMU has been compiled with the <code class="docutils literal notranslate"><span class="pre">simple</span></code> tracing backend.</div></blockquote> </dd></dl> <dl class="option"> <dt id="cmdoption-qemu-pr-helper-u"> <code class="descname">-u</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--user</code><code class="descclassname">=USER</code><a class="headerlink" href="#cmdoption-qemu-pr-helper-u" title="Permalink to this definition">¶</a></dt> <dd><p>user to drop privileges to</p> </dd></dl> <dl class="option"> <dt id="cmdoption-qemu-pr-helper-g"> <code class="descname">-g</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--group</code><code class="descclassname">=GROUP</code><a class="headerlink" href="#cmdoption-qemu-pr-helper-g" title="Permalink to this definition">¶</a></dt> <dd><p>group to drop privileges to</p> </dd></dl> <dl class="option"> <dt id="cmdoption-qemu-pr-helper-h"> <code class="descname">-h</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--help</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-qemu-pr-helper-h" title="Permalink to this definition">¶</a></dt> <dd><p>Display a help message and exit.</p> </dd></dl> <dl class="option"> <dt id="cmdoption-qemu-pr-helper-version"> <code class="descname">-V</code><code class="descclassname"></code><code class="descclassname">, </code><code class="descname">--version</code><code class="descclassname"></code><a class="headerlink" href="#cmdoption-qemu-pr-helper-version" title="Permalink to this definition">¶</a></dt> <dd><p>Display version information and exit.</p> </dd></dl> </div> </div> </div> </div> <footer> <div class="rst-footer-buttons" role="navigation" aria-label="footer navigation"> <a href="qemu-trace-stap.html" class="btn btn-neutral float-right" title="QEMU SystemTap trace tool" accesskey="n" rel="next">Next <span class="fa fa-arrow-circle-right"></span></a> <a href="qemu-nbd.html" class="btn btn-neutral" title="QEMU Disk Network Block Device Server" accesskey="p" rel="prev"><span class="fa fa-arrow-circle-left"></span> Previous</a> </div> <hr/> <div role="contentinfo"> <p> © Copyright 2021, The QEMU Project Developers. </p> </div> Built with <a href="http://sphinx-doc.org/">Sphinx</a> using a <a href="https://github.com/rtfd/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>. <!-- Empty para to force a blank line after "Built with Sphinx ..." --> <p></p> <p>This documentation is for QEMU version 6.2.0.</p> <p><a href="../about/license.html">QEMU and this manual are released under the GNU General Public License, version 2.</a></p> </footer> </div> </div> </section> </div> <script type="text/javascript"> var DOCUMENTATION_OPTIONS = { URL_ROOT:'../', VERSION:'qemu-kvm-6.2.0-53.module+el8.10.0+2055+8eb7870b.4', LANGUAGE:'None', COLLAPSE_INDEX:false, FILE_SUFFIX:'.html', HAS_SOURCE: false, SOURCELINK_SUFFIX: '.txt' }; </script> <script type="text/javascript" src="../_static/jquery.js"></script> <script type="text/javascript" src="../_static/underscore.js"></script> <script type="text/javascript" src="../_static/doctools.js"></script> <script type="text/javascript" src="../_static/js/theme.js"></script> <script type="text/javascript"> jQuery(function () { SphinxRtdTheme.Navigation.enable(true); }); </script> </body> </html>