title: install proxmox from usb device error
body: <p>I try to install Proxmox using a USB, and when I click to install, I see the next error:</p>
  
  <pre><code>testing cdrom /dev/sr0
  umount: can't umount /mnt: Invalid argument
  testing again in 5 seconds
  </code></pre>
  
  <p>Finally:</p>
  
  <pre><code>no cdrom found - unable to continue (type exit or CTRL-D to reboot)
  </code></pre>
  
  <p>I prepare the USB using ImageUSB in Windows, and it does have the previous fail, then I try to prepare in Ubuntu using <code>dd if=pve-cd.iso of=/dev/XYZ bs=1M</code>, I don't know where is the problem.</p>