Update main docs

static/docs/main/_sources/contents/overlays.rst.txt

@@ -162,6 +162,22 @@ built. Specific overlays can be selected with ``-O`` flag. For
 debugging purposes the templates can be written to a directory given
 via the ``-o`` flag.
 
+On clusters with large numbers of nodes a significant speedup can be achieved
+by building overlays in parallel. Adding parallel overlay building to `wwctl`
+is planned, see issue `#1087 <https://github.com/warewulf/warewulf/issues/1087>`_.
+Until parallel overlay building is implemented, builds can be easily done in 
+parallel with Gnu `parallel` or `xargs`, for example:
+
+.. code-block:: console
+
+  # Gnu parallel
+  wwctl node list | awk '{print $1}' | grep -v "NODE " | parallel -j 12 \
+    wwctl overlay build -N {}
+
+  # xargs
+  wwctl node list | awk '{print $1}' | grep -v "NODE " | xargs -n 1 -P 12 \
+    wwctl overlay build -N
+
 By default Warewulf will build/update and cache overlays as needed
 (configurable in the ``warewulf.conf``).
 

static/docs/main/contents/overlays.html

@@ -275,6 +275,20 @@ <h3>Build<a class="headerlink" href="#build" title="Link to this heading"></a
 built. Specific overlays can be selected with <code class="docutils literal notranslate"><span class="pre">-O</span></code> flag. For
 debugging purposes the templates can be written to a directory given
 via the <code class="docutils literal notranslate"><span class="pre">-o</span></code> flag.</p>
+<p>On clusters with large numbers of nodes a significant speedup can be achieved
+by building overlays in parallel. Adding parallel overlay building to <cite>wwctl</cite>
+is planned, see issue <a class="reference external" href="https://github.com/warewulf/warewulf/issues/1087">#1087</a>.
+Until parallel overlay building is implemented, builds can be easily done in
+parallel with Gnu <cite>parallel</cite> or <cite>xargs</cite>, for example:</p>
+<div class="highlight-console notranslate"><div class="highlight"><pre><span></span><span class="gp"># </span>Gnu<span class="w"> </span>parallel
+<span class="go">wwctl node list | awk &#39;{print $1}&#39; | grep -v &quot;NODE &quot; | parallel -j 12 \</span>
+<span class="go">  wwctl overlay build -N {}</span>
+
+<span class="gp"># </span>xargs
+<span class="go">wwctl node list | awk &#39;{print $1}&#39; | grep -v &quot;NODE &quot; | xargs -n 1 -P 12 \</span>
+<span class="go">  wwctl overlay build -N</span>
+</pre></div>
+</div>
 <p>By default Warewulf will build/update and cache overlays as needed
 (configurable in the <code class="docutils literal notranslate"><span class="pre">warewulf.conf</span></code>).</p>
 </section>