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lifecycle-hooks/index.html

@@ -410,31 +410,62 @@
                 
                 <h2 id="executing_commands_before_and_after_updating">Executing commands before and after updating<a class="headerlink" href="#executing_commands_before_and_after_updating" title="Permanent link">&para;</a></h2>
 <blockquote>
-<p><strong>DO NOTE</strong>: Both commands are shell commands executed with <code>sh</code>, and therefore require the 
+<p><strong>DO NOTE</strong>: These are shell commands executed with <code>sh</code>, and therefore require the
 container to provide the <code>sh</code> executable.</p>
 </blockquote>
-<p>It is possible to execute a <em>pre-update</em> command and a <em>post-update</em> command 
-<strong>inside</strong> every container updated by watchtower. The <em>pre-update</em> command is 
-executed before stopping the container, and the <em>post-update</em> command is 
-executed after restarting the container.</p>
+<p>It is possible to execute <em>pre/post-check</em> and <em>pre/post-update</em> commands
+<strong>inside</strong> every container updated by watchtower.</p>
+<ul>
+<li>The <em>pre-check</em> command is executed for each container prior to every update cycle.</li>
+<li>The <em>pre-update</em> command is executed before stopping the container when an update is about to start.</li>
+<li>The <em>post-update</em> command is executed after restarting the updated container</li>
+<li>The <em>post-check</em> command is executed for each container post every update cycle.</li>
+</ul>
 <p>This feature is disabled by default. To enable it, you need to set the option
 <code>--enable-lifecycle-hooks</code> on the command line, or set the environment variable
 <code>WATCHTOWER_LIFECYCLE_HOOKS</code> to <code>true</code>.</p>
 <h3 id="specifying_update_commands">Specifying update commands<a class="headerlink" href="#specifying_update_commands" title="Permanent link">&para;</a></h3>
-<p>The commands are specified using docker container labels, with 
-<code>com.centurylinklabs.watchtower.lifecycle.pre-update-command</code> for the <em>pre-update</em> 
-command and <code>com.centurylinklabs.watchtower.lifecycle.post-update</code> for the
-<em>post-update</em> command.</p>
-<p>These labels can be declared as instructions in a Dockerfile:</p>
-<pre><code class="docker">LABEL com.centurylinklabs.watchtower.lifecycle.pre-update=&quot;/dump-data.sh&quot;
+<p>The commands are specified using docker container labels, the following are currently available:</p>
+<table>
+<thead>
+<tr>
+<th>Type</th>
+<th>Docker Container Label</th>
+</tr>
+</thead>
+<tbody>
+<tr>
+<td>Pre Check</td>
+<td><code>com.centurylinklabs.watchtower.lifecycle.pre-check</code></td>
+</tr>
+<tr>
+<td>Pre Update</td>
+<td><code>com.centurylinklabs.watchtower.lifecycle.pre-update</code></td>
+</tr>
+<tr>
+<td>Post Update</td>
+<td><code>com.centurylinklabs.watchtower.lifecycle.post-update</code></td>
+</tr>
+<tr>
+<td>Post Check</td>
+<td><code>com.centurylinklabs.watchtower.lifecycle.post-check</code></td>
+</tr>
+</tbody>
+</table>
+<p>These labels can be declared as instructions in a Dockerfile (with some example .sh files):</p>
+<pre><code class="docker">LABEL com.centurylinklabs.watchtower.lifecycle.pre-check=&quot;/sync.sh&quot;
+LABEL com.centurylinklabs.watchtower.lifecycle.pre-update=&quot;/dump-data.sh&quot;
 LABEL com.centurylinklabs.watchtower.lifecycle.post-update=&quot;/restore-data.sh&quot;
+LABEL com.centurylinklabs.watchtower.lifecycle.post-check=&quot;/send-heartbeat.sh&quot;
 </code></pre>
 
 <p>Or be specified as part of the <code>docker run</code> command line:</p>
 <pre><code class="bash">docker run -d \
+  --label=com.centurylinklabs.watchtower.lifecycle.pre-check=&quot;/sync.sh&quot; \
   --label=com.centurylinklabs.watchtower.lifecycle.pre-update=&quot;/dump-data.sh&quot; \
   --label=com.centurylinklabs.watchtower.lifecycle.post-update=&quot;/restore-data.sh&quot; \
   someimage
+  --label=com.centurylinklabs.watchtower.lifecycle.post-check=&quot;/send-heartbeat.sh&quot; \
 </code></pre>
 
 <h3 id="execution_failure">Execution failure<a class="headerlink" href="#execution_failure" title="Permanent link">&para;</a></h3>