prerm is in util-linux 2.20.1-5.1ubuntu20.
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 | #! /bin/sh
set -e
case "$1" in
remove)
update-alternatives --remove pager /bin/more
update-alternatives --remove pager /usr/bin/pg
;;
upgrade|failed-upgrade|deconfigure)
;;
esac
|