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<section id="stateless">
<span id="id1"></span><h1>Stateless<a class="headerlink" href="#stateless" title="Link to this heading"></a></h1>
<p>In most operating systems, user data, system data, and configuration files
can become intermingled, which can make them challenging to manage.</p>
<figure class="align-center" id="id2">
<a class="reference internal image-reference" href="../../_images/stateless-1.png"><img alt="Stateless: User and system files mixed" src="../../_images/stateless-1.png" style="width: 412.2px; height: 225.0px;" />
</a>
<figcaption>
<p><span class="caption-text">Figure 1: Without stateless, user and system files become mixed on the filesystem over time.</span><a class="headerlink" href="#id2" title="Link to this image"></a></p>
</figcaption>
</figure>
<p>Clear Linux* OS has a stateless design philosophy with the goal to provide an
<abbr title="operating system">OS</abbr> that functions without excessive user
configuration or customization. Stateless in this context does <em>not</em> mean
ephemeral or non-persistent.</p>
<nav class="contents local" id="contents">
<ul class="simple">
<li><p><a class="reference internal" href="#file-level-separation" id="id4">File-level separation</a></p></li>
<li><p><a class="reference internal" href="#software-configuration" id="id5">Software configuration</a></p></li>
<li><p><a class="reference internal" href="#system-reset" id="id6">System reset</a></p></li>
<li><p><a class="reference internal" href="#additional-information" id="id7">Additional information</a></p></li>
</ul>
</nav>
<section id="file-level-separation">
<h2><a class="toc-backref" href="#id4" role="doc-backlink">File-level separation</a><a class="headerlink" href="#file-level-separation" title="Link to this heading"></a></h2>
<p>To accomplish a stateless design, the Clear Linux OS filesystem hierarchy is separated
between user-owned areas and Clear Linux OS-owned areas.</p>
<figure class="align-center" id="id3">
<a class="reference internal image-reference" href="../../_images/stateless-2.png"><img alt="Stateless: User and system files separation" src="../../_images/stateless-2.png" style="width: 411.3px; height: 224.1px;" />
</a>
<figcaption>
<p><span class="caption-text">Figure 2: With stateless, user and system files are separated on the filesystem.</span><a class="headerlink" href="#id3" title="Link to this image"></a></p>
</figcaption>
</figure>
<section id="system-area">
<h3>System area<a class="headerlink" href="#system-area" title="Link to this heading"></a></h3>
<p>Files under the <code class="file docutils literal notranslate"><span class="pre">/usr</span></code> directory are managed by Clear Linux OS as system files
(except <code class="file docutils literal notranslate"><span class="pre">/usr/local</span></code>).
Files written under the <code class="file docutils literal notranslate"><span class="pre">/usr</span></code> directory by users can get removed
through system updates with <a class="reference internal" href="swupd.html#swupd-guide"><span class="std std-ref">swupd</span></a>. This operating
assumption allows Clear Linux OS to verify and maintain integrity of system files.</p>
</section>
<section id="user-areas">
<h3>User areas<a class="headerlink" href="#user-areas" title="Link to this heading"></a></h3>
<p>Files under the <code class="file docutils literal notranslate"><span class="pre">/usr/local</span></code>, <code class="file docutils literal notranslate"><span class="pre">/etc/</span></code>, <code class="file docutils literal notranslate"><span class="pre">/opt</span></code>, <code class="file docutils literal notranslate"><span class="pre">/home</span></code>,
and <code class="file docutils literal notranslate"><span class="pre">/var</span></code> directories are owned and managed by the user. A freshly
installed Clear Linux OS system will only have a minimal set of files in the
<code class="file docutils literal notranslate"><span class="pre">/etc/</span></code> directory and software installed by Clear Linux OS does not write to
<code class="file docutils literal notranslate"><span class="pre">/etc</span></code>. This operating assumption allows Clear Linux OS users to clearly identify
the configuration that makes their system unique.</p>
</section>
</section>
<section id="software-configuration">
<h2><a class="toc-backref" href="#id5" role="doc-backlink">Software configuration</a><a class="headerlink" href="#software-configuration" title="Link to this heading"></a></h2>
<p>With stateless separation, default software configurations are read in order
from predefined source code, Clear Linux OS provided defaults, and user-provided
configuration.</p>
<section id="default-configurations">
<h3>Default configurations<a class="headerlink" href="#default-configurations" title="Link to this heading"></a></h3>
<p>Software in Clear Linux OS provides default configuration values so that it is
immediately functional, except for some that require additional configuration.</p>
<p>If an upstream software puts default configurations in multiple locations
such as <code class="file docutils literal notranslate"><span class="pre">/usr/</span></code> and <code class="file docutils literal notranslate"><span class="pre">/etc</span></code>, it will be modified by the Clear Linux OS
distro to comply with the stateless design. Also, some default configurations
may be modified to close security loopholes. Defaults will reside
under <code class="file docutils literal notranslate"><span class="pre">/usr/share/defaults</span></code>. These files can be referenced as
templates for customization.</p>
<p>For example, after installing the <cite>httpd</cite> bundle for Apache web server, its
default configurations appear in the <code class="file docutils literal notranslate"><span class="pre">/usr/share/defaults/httpd/</span></code> directory.</p>
</section>
<section id="overriding-configurations">
<h3>Overriding configurations<a class="headerlink" href="#overriding-configurations" title="Link to this heading"></a></h3>
<p>If a configuration needs to be changed, the appropriate file should be
modified by the user under <code class="file docutils literal notranslate"><span class="pre">/etc/</span></code>. If the configuration file does not
already exist, it can be created in the appropriate location.</p>
<p>User-defined configuration files should contain the minimal set of desired
changes and rely on default configuration for the rest.</p>
<p>For example, a customized Apache configuration can be used instead by:</p>
<ol class="arabic">
<li><p>Install the Apache web server bundle.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>swupd<span class="w"> </span>bundle-add<span class="w"> </span>httpd
</pre></div>
</div>
</li>
<li><p>Create the destination directory for the configuration.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>mkdir<span class="w"> </span>/etc/httpd
</pre></div>
</div>
</li>
<li><p>Copy the default configuration as a reference template.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>cp<span class="w"> </span>/usr/share/defaults/httpd/httpd.conf<span class="w"> </span>/etc/httpd/
</pre></div>
</div>
</li>
<li><p>Make any desired modifications to the configurations.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudoedit<span class="w"> </span>/etc/httpd/httpd.conf
</pre></div>
</div>
</li>
<li><p>Reload the service or reboot the system to pickup any changes.</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>systemctl<span class="w"> </span>daemon-reload<span class="w"> </span>httpd<span class="w"> </span><span class="o">&amp;&amp;</span><span class="w"> </span>systemctl<span class="w"> </span>restart<span class="w"> </span>httpd
</pre></div>
</div>
</li>
</ol>
<p>This pattern can be used to modify the configurations of other programs too.
The <a class="reference external" href="https://github.com/clearlinux/clr-man-pages/blob/master/stateless.7.rst">stateless man page</a> has application-specific examples.</p>
</section>
</section>
<section id="system-reset">
<h2><a class="toc-backref" href="#id6" role="doc-backlink">System reset</a><a class="headerlink" href="#system-reset" title="Link to this heading"></a></h2>
<p>One advantage of the stateless design is that the system defaults can be
easily restored by simply deleting everything under <code class="file docutils literal notranslate"><span class="pre">/etc/</span></code> and
<code class="file docutils literal notranslate"><span class="pre">/var</span></code>.</p>
<p>Running the commands below effectively performs a system reset as if it was
just installed:</p>
<div class="highlight-bash notranslate"><div class="highlight"><pre><span></span>sudo<span class="w"> </span>rm<span class="w"> </span>-rf<span class="w"> </span>/etc
sudo<span class="w"> </span>rm<span class="w"> </span>-rf<span class="w"> </span>/var
</pre></div>
</div>
<p>In other Linux distributions, this can be a catastrophic action that may render
a system unable to boot and/or inaccessible.</p>
</section>
<section id="additional-information">
<h2><a class="toc-backref" href="#id7" role="doc-backlink">Additional information</a><a class="headerlink" href="#additional-information" title="Link to this heading"></a></h2>
<ul class="simple">
<li><p><a class="reference external" href="https://github.com/clearlinux/clr-man-pages/blob/master/stateless.7.rst">stateless man page</a></p></li>
<li><p><a class="reference internal" href="../kernel/firmware.html#firmware"><span class="std std-ref">Firmware</span></a></p></li>
</ul>
</section>
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<h3><a href="../../index.html">Table of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Stateless</a><ul>
<li><a class="reference internal" href="#file-level-separation">File-level separation</a><ul>
<li><a class="reference internal" href="#system-area">System area</a></li>
<li><a class="reference internal" href="#user-areas">User areas</a></li>
</ul>
</li>
<li><a class="reference internal" href="#software-configuration">Software configuration</a><ul>
<li><a class="reference internal" href="#default-configurations">Default configurations</a></li>
<li><a class="reference internal" href="#overriding-configurations">Overriding configurations</a></li>
</ul>
</li>
<li><a class="reference internal" href="#system-reset">System reset</a></li>
<li><a class="reference internal" href="#additional-information">Additional information</a></li>
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