title: suspend then wake: cron of rtcwake, Beaglebone Black
body: <p>I'm trying to configure the beaglebone black [wireless version - 4.9.82-ti-r102 #1 SMP PREEMPT] -- running debian 9.3 stretch.</p>
  
  <p>This command works fine in a bash terminal:</p>
  
  <pre><code>sudo /usr/sbin/rtcwake -m mem -u -t $(date +%s -d "+2 minutes")
  </code></pre>
  
  <p>I've setup a cron job via </p>
  
  <pre><code>sudo crontab -e
  </code></pre>
  
  <p>In it, I have the following line:</p>
  
  <pre><code>10,40 * * * * /usr/sbin/rtcwake -m mem -u -t $(date +%s -d "20 minutes")
  </code></pre>
  
  <p>However, the device is not suspending.</p>
  
  <p>What am I doing wrong?  How do I debug this?</p>
  
  <p>Thanks for your help</p>
  
  <p>M</p>