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From: siegman@sierra.STANFORD.EDU (siegman)
Newsgroups: comp.sys.mac.apps
Subject: How the System Installer Works (Important)
Keywords: Installer
Message-ID: <85@sierra.STANFORD.EDU>
Date: 16 Jan 91 20:36:25 GMT
Distribution: comp.sys.mac.apps
Organization: Stanford University
Lines: 26

(At least, it seems important to me.)

   When I encounter system problems after a power failure or crash, I
have previously reinstalled my system file using the Installer program
on a locked System Tools disk.  Until now I'd thought this should
completely relace and repair any damage to the system file.

   A Mac expert here at Stanford, who should know about these things,
says that running the Installer to a HD with the old system file still
in place does NOT replace or repair damaged resources.  The Installer
checks that needed system resources are present, and updates them with
the latest version if necessary; but it has no way to check that a
resource might be internally damaged, and it does not replace all
resources, only outdated ones.

   To really repair a damaged system, the drill is apparently to save
DAs and fonts from the old system; start up from the System Tools
disk; trash the old system file (and the Finder also? -- I don't
know); then run the Installer.  Doing this cured the Excel menus
problem I posted about earlier (as pointed out also by Rex Sanders).

   This information is second-hand, and I'm not a Mac expert, but I
think this is the real skinny on what the Installer does, and doesn't,
do.  [It also strikes me as the WRONG way to do things, but that's
another matter.]  It may be the solution to a lot of mysterious
problems with applications and with Mac systems generally.