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Date:      Tue, 13 Feb 2001 21:51:47 -0800
From:      Doug Barton <DougB@gorean.org>
To:        Brian Behlendorf <brian@collab.net>
Cc:        Greg Troxel <gdt@fnord.ir.bbn.com>, freebsd-stable@FreeBSD.ORG, Kris Kennaway <kris@obsecurity.org>
Subject:   Upgrading config files (Was: Re: sshd in 4.2-STABLE)
Message-ID:  <3A8A1CF3.264A5C70@gorean.org>
References:  <Pine.BSF.4.31.0102130807430.863-100000@localhost>

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Brian Behlendorf wrote:
> 
> On 13 Feb 2001, Greg Troxel wrote:
> > The Debian package system does something like this, and I found it
> > very helpful for the brief time I ran a GNU/Linux system.  IIRC,
> > packages distinguished between regular files (that weren't expected to
> > change) and configuration files.  When upgrading to a new version of a
> > package, the rule was that if a config file was unchanged (same md5)
> > from the installed package, it was replaced by the new version.  If
> > changed, the user was asked to merge/cope.  Also, config files were
> > left on pkg_delete (well, dpkg --remove), unless one asked to have
> > them removed.

	My mm hacking time has been taken up recently by the more urgent nature
of the BIND mess which has taken up extra work and "free(bsd)" time.
However I've given a lot of thought to this MD5 scenario that you and a
few others have suggested in the past. As much as I loathe the concept
of automatically updating files without the user looking at the changes
first, the request comes up so often that it's probably going to have to
happen in one form or another. 

	My preferred method of automatic updates is some sort of cvs-related
system, however I think an MD5 based system will be (marginally) easier
to implement (once a few hurdles are overcome) and will help more users. 

> I have to agree - many of the changes mergemaster makes are to files that
> no one would recommend editing directly in regular use, like MAKEDEV and
> /etc/rc.network and all the stuff in /etc/defaults.  Modifying mergemaster
> to only ask to merge files that have been changed sounds like a good idea
> to me...

	Well, it definitely sounds like the easy way out. Whether it's a good
idea or not is a whole other question. There are 4 corners to the
equation... automatic upgrade or not, and force the users to see and
approve the changes or not. Mergemaster takes the most paranoid approach
by default, that of not automatically upgrading, AND forcing the user to
see and approve of the changes. I made that decision because I felt
strongly that the sysadmin SHOULD be looking at the changes before they
go into the system. You can feel free to repeat the "tools not policy"
mantra, but mm is my tool. My feeling was that if someone wanted to
create another tool that did automatic upgrades, they should feel free
to do that. (Small, lightweight tools, etc. etc.) However, in some
measure to my chagrin (although much to my gratification) mm is now seen
as "the" way to upgrade your config files. 

	So, the question now is, does upgrading by default without forcing the
user to see the changes unload the gun, or just point it at a different
foot? My feeling is that all we're doing is replacing one set of
problems with another, and losing the opportunity to educate the users
in the process. I have long been an advocate of both making "The Right
Thing" easier to understand and to accomplish, but at some level you
just can't make unix system administration any easier. 

Doug


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