Comment 3 for bug 176883

This is because you're using bash as your default /bin/sh (rather than the Ubuntu default of dash). I fixed this a while back for Ubuntu 8.04:

partman-partitioning (54ubuntu5) hardy; urgency=low

  * Backport from trunk:
    - Only disable swap on devices that are being changed (LP: #199048).
      Requires partman-base (>= 114ubuntu4).
  * Move 'local' down a line in create_new_partition in order to work
    properly with bash, which initialises local variables without an
    accompanying assignment to empty rather than to any previous value.

 -- Colin Watson <email address hidden> Fri, 21 Mar 2008 00:27:06 +0000