prerm is in maas-region-controller-min 1.5+bzr2252-0ubuntu1.
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 | #!/bin/sh
set -e
. /usr/share/debconf/confmodule
invoke-rc.d apache2 stop || true
|