using dd to clone a usb drive

From
https://www.garron.me/en/bits/convert-store-copy-bootable-usb-iso-file-another-usb.html

• use df to find the device name, then
• dd if=/src/dev/path of=/dest/dev/path conv=notrunc
  for example dest can be a file also - 
  dd if=/dev/sdc of=/home/user/backup-usb.dd conv=notrunc
  
  (notrunc is useful only when writing to a file, https://stackoverflow.com/questions/20526198/why-using-conv-notrunc-when-cloning-a-disk-with-dd )