<figure class="image"><img src="https://images.unsplash.com/photo-1558946104-35820fc709ba?crop=entropy&amp;cs=tinysrgb&amp;fit=max&amp;fm=jpg&amp;ixid=M3wxNTQwMTB8MHwxfHNlYXJjaHw5Nnx8bGF1bmNofGVufDB8fHx8MTc0Njg4NDE4OXww&amp;ixlib=rb-4.1.0&amp;q=80&amp;w=1080"><figcaption>Photo by <a target="_blank" rel="noopener noreferrer" href="https://unsplash.com/@mcovoy?utm_source=DNX&amp;utm_medium=referral">Makoto Tsuka</a> on <a target="_blank" rel="noopener noreferrer" href="https://unsplash.com/?utm_source=DNX&amp;utm_medium=referral">Unsplash</a></figcaption></figure><h3>Problem</h3><p>We noticed that our scheduled <code>cron</code>/<code>launchd</code> job — responsible for restoring backups via <code>scp</code> — was intermittently failing. Logs showed:</p><pre><code class="language-plaintext">SCP failed
</code></pre><p>Upon closer inspection, the failure was <strong>not due to permissions or file corruption</strong>, but rather that <strong>only a partial set of files (e.g., 106 out of 207) were transferred</strong> before the connection dropped.</p><h3>Root Cause</h3><p>The issue was traced back to <strong>macOS going to sleep during the job</strong>. Since the job ran early in the morning with the lid closed, the system entered sleep mid-transfer — interrupting the active <code>scp</code> session.</p><h3>Solution</h3><p>We wrapped the job with <code>caffeinate</code> to prevent sleep during execution:</p><pre><code class="language-xml">&lt;key&gt;ProgramArguments&lt;/key&gt;
&lt;array&gt;
  &lt;string&gt;/usr/bin/caffeinate&lt;/string&gt;
  &lt;string&gt;-s&lt;/string&gt;
  &lt;string&gt;/Users/adamcai/Projects/ss-db/restore.sh&lt;/string&gt;
&lt;/array&gt;
</code></pre><p>The <code>-s</code> flag keeps the <strong>system (not just the display)</strong> awake while the script runs. This ensures that <code>scp</code> completes without being cut off by sleep.</p><h3>Result</h3><p>After applying this fix, the backup restore job ran reliably every morning — with all files successfully transferred.</p>

A scheduled launchd job using scp failed to complete because macOS went to sleep mid-transfer, interrupting the connection. Adding caffeinate -s to the job prevented system sleep during execution, resolving the issue and ensuring all files transferred reliably.

All Posts In Launchd