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<li class="toctree-l3"><a class="reference internal" href="../howto/storage_buckets/">Manage buckets</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/storage_create_instance/">Create an instance in a pool</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/storage_backup_volume/">Back up a volume</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/storage_move_volume/">Move or copy a volume</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/storage_csi/">Use the LXD CSI driver with Kubernetes</a></li>
</ul>
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<li class="toctree-l3"><a class="reference internal" href="../howto/network_create/">Create a network</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_configure/">Configure a network</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_bgp/">Configure as BGP server</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_acls/">Configure network ACLs</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_forwards/">Configure forwards</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_zones/">Configure network zones</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_bridge_firewalld/">Configure your firewall</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_bridge_resolved/">Integrate with resolved</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_ovn_setup/">Set up OVN</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_load_balancers/">Configure load balancers</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_ovn_peers/">Configure peer routing</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_ipam/">Display IPAM information</a></li>
</ul>
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<li class="toctree-l3"><a class="reference internal" href="../howto/cluster_form/">Form a cluster</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/cluster_manage/">Manage a cluster</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/cluster_config_networks/">Configure networks</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/cluster_config_storage/">Configure storage</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/cluster_manage_instance/">Manage instances</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/cluster_groups/">Set up cluster groups</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/cluster_placement_groups/">Use placement groups</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/cluster_recover/">Recover a cluster</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/cluster_vip/">Set up a highly available virtual IP</a></li>
</ul>
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<li class="toctree-l2 has-children"><a class="reference internal" href="../production-setup/">Production setup</a><input aria-label="Toggle navigation of Production setup" class="toctree-checkbox" id="toctree-checkbox-11" name="toctree-checkbox-11" role="switch" type="checkbox"/><label for="toctree-checkbox-11"><span class="icon"><svg><use href="#svg-arrow-right"></use></svg></span></label><ul>
<li class="toctree-l3"><a class="reference internal" href="../howto/benchmark_performance/">Benchmark performance</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/network_increase_bandwidth/">Increase bandwidth</a></li>
<li class="toctree-l3"><a class="reference internal" href="../metrics/">Monitor metrics</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/logs_loki/">Send logs to Loki</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/grafana/">Set up Grafana</a></li>
<li class="toctree-l3"><a class="reference internal" href="../backup/">Back up a server</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/disaster_recovery/">Recover instances</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/disaster_recovery_replication/">Disaster recovery with storage replication</a></li>
</ul>
</li>
<li class="toctree-l2"><a class="reference internal" href="../howto/snap/">Manage the snap</a></li>
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<li class="toctree-l3"><a class="reference internal" href="../howto/network_bridge_firewalld/">Configure your firewall</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/instances_troubleshoot/">Troubleshoot instances</a></li>
<li class="toctree-l3"><a class="reference internal" href="../howto/dqlite_troubleshoot/">Troubleshoot Dqlite</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../howto/auth_bearer/">How to authenticate to the LXD API using bearer tokens</a></li>
<li class="toctree-l2"><a class="reference internal" href="../howto/devlxd_authenticate/">How to authenticate to the DevLXD API</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../explanation/lxd_lxc/"><code class="docutils literal notranslate"><span class="pre">lxd</span></code> and <code class="docutils literal notranslate"><span class="pre">lxc</span></code></a></li>
<li class="toctree-l2"><a class="reference internal" href="../explanation/instances/">Containers and VMs</a></li>
<li class="toctree-l2"><a class="reference internal" href="../image-handling/">Local and remote images</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../explanation/networks/">Networking setups</a></li>
<li class="toctree-l2"><a class="reference internal" href="../database/">The LXD Dqlite database</a></li>
<li class="toctree-l2"><a class="reference internal" href="../explanation/lxc_show_info/"><code class="docutils literal notranslate"><span class="pre">lxc</span></code> <code class="docutils literal notranslate"><span class="pre">show</span></code> and <code class="docutils literal notranslate"><span class="pre">info</span></code></a></li>
<li class="toctree-l2"><a class="reference internal" href="../authentication/">Remote API authentication</a></li>
<li class="toctree-l2"><a class="reference internal" href="../explanation/authorization/">Remote API authorization</a></li>
<li class="toctree-l2"><a class="reference internal" href="../explanation/projects/">Instances grouping with projects</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../explanation/bpf/">Privilege delegation using BPF Token</a></li>
<li class="toctree-l2"><a class="reference internal" href="../explanation/csi/">The LXD CSI driver</a></li>
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<li class="toctree-l3"><a class="reference internal" href="../reference/release-notes/release-notes-6.7/">LXD 6.7</a></li>
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<li class="toctree-l3"><a class="reference internal" href="../reference/instance_properties/">Instance properties</a></li>
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<li class="toctree-l4"><a class="reference internal" href="../reference/standard_devices/">Standard devices</a></li>
<li class="toctree-l4"><a class="reference internal" href="../reference/devices_none/">Type: <code class="docutils literal notranslate"><span class="pre">none</span></code></a></li>
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<li class="toctree-l3"><a class="reference internal" href="../reference/instance_units/">Units for storage and network limits</a></li>
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<article role="main" id="furo-main-content">
<section id="communication-between-instance-and-host">
<span id="dev-lxd"></span><h1>Communication between instance and host<a class="headerlink" href="#communication-between-instance-and-host" title="Link to this heading">¶</a></h1>
<p class="youtube_link">
<a href="https://www.youtube.com/watch?v=xZSnqqWykmo" target="_blank">
<span title="The LXD instance API" class="play_icon">▶</span>
<span title="The LXD instance API">Watch on YouTube</span>
</a>
</p>
<p>The DevLXD API allows for limited communication between guest instances and the host.</p>
<p>The API is available inside each LXD guest as a Unix socket at <code class="docutils literal notranslate"><span class="pre">/dev/lxd/sock</span></code>, using JSON over plain HTTP.
Multiple concurrent connections are allowed.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p><a class="configref reference internal" href="../reference/instance_options/#instance-security:security.devlxd"><code class="docutils literal notranslate"><span class="pre">security.devlxd</span></code></a> must be set to <code class="docutils literal notranslate"><span class="pre">true</span></code> (which is the default) for an instance to allow access to the socket.</p>
<p>Additionally, for virtual machines, the LXD agent must be present and running for the socket to be available.</p>
</div>
<section id="implementation-details">
<span id="dev-lxd-implementation"></span><h2>Implementation details<a class="headerlink" href="#implementation-details" title="Link to this heading">¶</a></h2>
<section id="containers">
<span id="dev-lxd-implementation-containers"></span><h3>Containers<a class="headerlink" href="#containers" title="Link to this heading">¶</a></h3>
<p>LXD on the host binds <code class="docutils literal notranslate"><span class="pre">/var/lib/lxd/devlxd/sock</span></code> and listens for connections.
This single socket is exposed into every container started by LXD at <code class="docutils literal notranslate"><span class="pre">/dev/lxd/sock</span></code>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>The alternative to using a single socket is to create a socket for every container.
This approach was discarded to avoid issues with file descriptor limits for hosts with thousands of containers.</p>
</div>
</section>
<section id="virtual-machines">
<span id="dev-lxd-implementation-vms"></span><h3>Virtual machines<a class="headerlink" href="#virtual-machines" title="Link to this heading">¶</a></h3>
<p>LXD on the host starts a HTTPS <abbr title="Virtual Socket">Vsock</abbr> server.
The LXD agent on the virtual machine communicates securely with the Vsock server using a certificate mounted in the VM’s configuration drive.
The LXD agent creates the socket at <code class="docutils literal notranslate"><span class="pre">/dev/lxd/sock</span></code> and proxies requests to the Vsock server.</p>
</section>
</section>
<section id="authentication">
<span id="devlxd-authentication"></span><h2>Authentication<a class="headerlink" href="#authentication" title="Link to this heading">¶</a></h2>
<p>Queries on <code class="docutils literal notranslate"><span class="pre">/dev/lxd/sock</span></code> only return information related to the requesting instance.</p>
<p>For containers, LXD inspects user credentials associated with the connection and matches them with a running instance.</p>
<p>For virtual machines, LXD extracts the virtual socket ID from the remote address of the caller (the LXD agent), and matches it with a virtual machine.</p>
<section id="bearer-tokens">
<span id="devlxd-authentication-bearer"></span><h3>Bearer tokens<a class="headerlink" href="#bearer-tokens" title="Link to this heading">¶</a></h3>
<p>Processes within guest instances can now authenticate over the DevLXD socket using a bearer token.
To do this, set an <code class="docutils literal notranslate"><span class="pre">Authorization:</span> <span class="pre">Bearer</span> <span class="pre">{token}</span></code> header on requests to the socket.</p>
<p>Bearer tokens can be obtained by creating a <code class="docutils literal notranslate"><span class="pre">DevLXD</span> <span class="pre">token</span> <span class="pre">bearer</span></code> identity in the identities API and issuing a token for it.
For more information, see <a class="reference internal" href="../howto/devlxd_authenticate/#devlxd-authenticate"><span class="std std-ref">How to authenticate to the DevLXD API</span></a>.</p>
</section>
</section>
<section id="rest-api">
<span id="devlxd-api-spec"></span><h2>REST-API<a class="headerlink" href="#rest-api" title="Link to this heading">¶</a></h2>
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Contents
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<ul>
<li><a class="reference internal" href="#">Communication between instance and host</a><ul>
<li><a class="reference internal" href="#implementation-details">Implementation details</a><ul>
<li><a class="reference internal" href="#containers">Containers</a></li>
<li><a class="reference internal" href="#virtual-machines">Virtual machines</a></li>
</ul>
</li>
<li><a class="reference internal" href="#authentication">Authentication</a><ul>
<li><a class="reference internal" href="#bearer-tokens">Bearer tokens</a></li>
</ul>
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<li><a class="reference internal" href="#rest-api">REST-API</a></li>
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