title: How to use Overlayfs in Linux 3.19 to mount multiple lowerdir
body: <p>There has been a similar <a href="https://stackoverflow.com/questions/31044982/how-to-use-multiple-lower-layers-in-overlayfs">question</a> with an answer pointing towards Overlay being built into the 3.19 Linux Kernel that will support multiple lower layers. The link an answer provides (and other pages I've stumbled across) doesn't supply any information about how to do this in Linux 3.19 and only states that it is possible.</p>
  
  <p>I am currently running on 3.19 an having a problem trying to get multiple lower layers to overlay.</p>
  
  <p>From what I've read to mount an overlay with multiple <code>lowerdir</code>s looks like this</p>
  
  <pre><code>    mount -t overlay overlay -o lowerdir=/firstlower:/secondlower,upperdir=/upper/root,workdir=/upper/workdir /merged
  </code></pre>
  
  <p>where the two lower layers are colon-separated. I've not been able to find a reliable enough source to confirm this information though so I'm hoping this post will help.</p>
  
  <p>Using the above code renders an error:</p>
  
  <pre><code>      overlayfs: failed to resolve '/firstlower:/secondlower': -2
        mount: mounting overlay on /merged failed: Invalid argument
  </code></pre>
  
  <p>Does anyone know what is going wrong? I know that I can overlay these two lower layers and then overlay the result again but I want to be able to do this on one line due to the requirement of having a <code>workdir</code> in the 3.19 Overlay which I want to be absent from either of our lower layers.</p>