title: How to update tar file that has gzip compression
body: <p>I executed:</p>
  
  <pre><code>tar -Ppcfz backup.tar.gz on /location/
  </code></pre>
  
  <p>This will:
  Create a new tar file for the /location/
  Preserve paths,
  Preserve permissions,
  Compress using gzip</p>
  
  <p>I need to later update this tar file with files from /location/ that have not been added or are new:</p>
  
  <pre><code>tar -Ppuf backup.tar.gz /location/
  </code></pre>
  
  <p>I get errors:</p>
  
  <blockquote>
    <p>tar: This does not look like a tar archive tar: Skipping to next
    header tar: Archive contains obsolescent base-64 headers tar:
    Unexpected EOF in archive tar: Error is not recoverable: exiting now</p>
  </blockquote>
  
  <p>Help please.</p>