postrm is in zentyal-firewall 2.3.9+quantal1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | #!/bin/bash
set -e
case "$1" in
    purge)
        # purge configuration
        /usr/share/zentyal/purge-module firewall
    ;;
    remove)
        dpkg-trigger --no-await zentyal-core
    ;;
esac
exit 0
 |