docs: def connect(image):
      '''
      Activate nbd for an image file.
  
      CLI Example:
  
      .. code-block:: bash
  
          salt '*' qemu_nbd.connect /tmp/image.raw
      '''
      if not os.path.isfile(image):
          log.warning('Could not connect image: %s does not exist', image)
          return ''
  
      if salt.utils.path.which('sfdisk'):
          fdisk = 'sfdisk -d'
      else:
          fdisk = 'fdisk -l'
      __salt__['cmd.run']('modprobe nbd max_part=63')
      for nbd in glob.glob('/dev/nbd?'):
          if __salt__['cmd.retcode']('{0} {1}'.format(fdisk, nbd)):
              while True:
                  # Sometimes nbd does not "take hold", loop until we can verify
                  __salt__['cmd.run'](
                          'qemu-nbd -c {0} {1}'.format(nbd, image),
                          python_shell=False,
                          )
                  if not __salt__['cmd.retcode']('{0} {1}'.format(fdisk, nbd)):
                      break
              return nbd
      log.warning('Could not connect image: %s', image)
      return ''