luksbackup: a tool for backing up GnuPG keys and entire directories to luks-encrypted devices

* You will probably need to run this as root.

* Note that device names should not include the /dev/ prefix.
  They are assumed to only consist of the last part, i.e. 'sdb1'.

* Backing up private keys
** Use the -k flag to back up your private GnuPG keys to a 'gnupg' directory on the target devices
    usage: ./luksbackup.sh -k device1 device2 ...

* Backing up a directory
** Use the -d flag to back up a directory
    usage: ./luksbackup.sh -d srcdir device1 device2 ...