postrm is in monitoring-plugins-basic 2.1.2-2ubuntu2.
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/sh
set -e
BASIC_PLUGINS="apt dhcp disk dummy ftp http load mail news ntp ping procs real ssh tcp_udp telnet users"
if [ "$1" = "purge" ]; then
	if which ucf >/dev/null 2>&1; then
		have_ucf="yes"
	fi
	for f in $BASIC_PLUGINS; do
		rm -f /etc/nagios-plugins/config/${f}.cfg
		if [ "$have_ucf" = "yes" ]; then
			ucf --purge /etc/nagios-plugins/config/${f}.cfg
		fi
	done 
fi
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