On Mon, Sep 29, 2003 at 10:49:16AM +0100, David Laight wrote:
  | I think that we need to do the following:
  | 1) Do not (directly) install any files that the user might change.
  |    (master copies of some will be needed)
  | 2) Run a script (cf etcupdate and postinstall) that ensures that
  |    the required config files exist and contain the required entries.
  |    (needs to be able to be run on a system without a source tree!)

postinstall already does most of this.

postinstall can also run without a source tree; I regularly upgrade
a system by building the sets and copying them to a target system, and
then:
    a)	extracting all sets except etc.tgz to /
    b)	extract etc.tgz to a scratch dir and running
		./etc/postinstall -s `pwd` check
		./etc/postinstall -s `pwd` fix
No source is required ...