title: "bad variable name" in bash script started by cron
body: <p>Works just fine when running it manually on the shell but when I setup a cronjob to run it on reboot I get "bad variable name". </p>
  
  <pre><code>#! /bin/sh
  # /etc/init.d/duplicityCleanUp
  export PASSPHRASE=foo
  duplicity remove-older-than 30D --force --gio smb://remote/archiv/
  duplicity remove-all-but-n-full 1 --force --gio smb://remote/archiv/
  unset PASSPHRASE
  </code></pre>