title: How to solve "make: *** No rule to make target `out/target/product/generic/root/file_contexts', needed by `snod'. Stop."
body: <p>I am building the source code of android these days, and I encountered a problem and find It is hard to solve for me, the problem is :</p>
  
  <p>When I first build the whole source code ,I can get the right result, the <code>system.img</code>, <code>userdata.img</code>, <code>ramdisk.img</code> .. all the final <code>.img</code> exist, and then I try to do some modification to the apps in the folder <code>/packages/app/</code>, when I execute the command <code>make snod</code> and there comes an error :</p>
  
  <pre><code>make: *** No rule to make target `out/target/product/generic/root/file_contexts', needed by `snod'.  Stop.
  </code></pre>
  
  <p>The entire steps I excute is :</p>
  
  <pre><code>   # source build/envsetup.sh
     # lunch full-eng
     # mmm /package/apps/Calculator( just take Calculator for example)
     # make snod
  </code></pre>
  
  <p>but this time, I can't see and <code>.img</code> files in the folder <code>/out/target/product/generic</code>, I have no idea, Could anyone help me?</p>
  
  <p>Thank you..</p>