title: DD Command with Override
body: <p>I have a question regarding the dd command,
  Last week I used the following form:</p>
  
  <pre><code>sudo dd if=system.img of=/dev/sdb2 bs=1M
  # system.img has 512MB
  </code></pre>
  
  <p>But my image has undergone some changes and I had to run the same command again and I had the answer:</p>
  
  <pre><code>512 + 0 records in
  512 + 0 records out
  536870912 bytes (537 MB, 512 MiB) copied, 40.8683 s, 13.1 MB/s
  </code></pre>
  
  <p>Has the previous image been overwritten in SD?
  Why the 537 MB result?</p>