prerm is in fai-nfsroot 3.4.8ubuntu5.
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  | #!/bin/sh -e
case "$1" in
    remove|deconfigure|failed-upgrade)
	update-alternatives --remove policy-rc.d /usr/bin/policy-rc.d.fai
        ;;
esac
exit 0
 |