postinst is in rsh-redone-server 85-2.
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 | #!/bin/sh -e
if [ "$1" = configure ] && [ -z "$2" ]; then
	update-inetd --group BSD --add "shell		stream	tcp	nowait	root	/usr/sbin/tcpd	/usr/sbin/in.rshd"
	update-inetd --group BSD --add "login		stream	tcp	nowait	root	/usr/sbin/tcpd	/usr/sbin/in.rlogind"
else
	update-inetd --enable shell,login
fi
 |