prerm is in bind9 1:9.10.3.dfsg.P4-8.
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 18 19 20 21 22 23 24 25 26 27 28 29 30  | #!/bin/sh
set -e
case "$1" in
    remove)
	# if bind is running, stop it before removing
	if pidof named >/dev/null 2>&1; then
		# test if invoke-rc.d command is present on this system
		if command -v invoke-rc.d >/dev/null 2>&1; then
		    invoke-rc.d bind9 stop
		# if really not, use initscript
		else
		    /etc/init.d/bind9 stop
		fi
	fi
    ;;
    upgrade)
	# leave bind running during the upgrade
    ;;
    *)
	echo "prerm called with unknown argument \`$1'" >&2
	exit 1
    ;;
esac
exit 0
 |