postrm is in postfix-gld 1.7-3build1.
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  | #!/bin/sh
set -e
if [ "$1" = "purge" ] ; then
  update-rc.d gld remove > /dev/null
fi
 |