title: Why should one delete sstate-cache when deleting tmp in Yocto build?
body: <p>The section <a href="https://www.yoctoproject.org/docs/latest/ref-manual/ref-manual.html#structure-build-tmp" rel="nofollow noreferrer">5.2.7. build/tmp/</a> of the Yocto Reference Manual says:</p>
  
  <blockquote>
    <p>As a last resort, to clean up a build and start it from scratch (other than the downloads), you can remove everything in the <code>tmp</code> directory or get rid of the directory completely. If you do, you should also completely remove the <code>build/sstate-cache</code> directory.</p>
  </blockquote>
  
  <p>Does this mean that if one deletes the <code>tmp</code>, they should <em>always</em> delete <code>sstate-cache</code> as well and things break if they don't, or is it just a confusing formulation meaning it won't really be from scratch if the <code>sstate-cache</code> is still there?</p>
  
  <p>And if it is the former, what is the reason?</p>