postrm is in mgetty 1.1.36-3.1.
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  | #!/bin/sh -e
case "$1" in
    purge)
        # remove the configuration files in /etc/mgetty
        for file in mgetty.config dialin.config login.config; do
	    if [ -f /etc/mgetty/$file ] ; then
	    	rm -f /etc/mgetty/$file
	    fi
	    if [ -f /etc/mgetty/$file.dpkg-old ] ; then
	    	rm -f /etc/mgetty/$file.dpkg-old
	    fi
	    if [ -f /etc/mgetty/$file.dpkg-new ] ; then
	    	rm -f /etc/mgetty/$file.dpkg-new
	    fi
	done
	rmdir /etc/mgetty || true;
        rmdir /var/spool/fax/incoming /var/spool/fax || true;
	;;
    *)
	;;
esac
exit 0;
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