Should no-tweak mode become the default?

[Carl E. Thompson]

-------- Original Message  --------
Subject: Re: Should no-tweak mode become the default?
From: Wayne Davison <wayned at samba.org>
To: Matt McCutchen <matt at mattmccutchen.net>
Date: 05/09/2008 11:25 PM

> On Thu, May 08, 2008 at 09:34:07PM -0400, Matt McCutchen wrote:
>> This is to continue my discussion with Carl [...] about whether
>> no-tweak mode should become rsync's default when --inplace is not
>> specified.
> 
> I completely reject this idea.  The --inplace option is all about data
> updating, not attribute updating.  Most of the time when I'm copying
> things, I want rsync to modify file attributes in-place, and I almost
> never want it to modify a file's content in-place.  So joining those
> two disparate things into a single option would be counter productive.
> 
> I also don't want to change the default because most of the time when a
> user is using rsync ad-hoc, it is not being used for a backup.  When it
> is, the command has usually been setup in a script that we can expect
> to have been configured with the right options.  So, I think changing
> rsync's default would inconvenience users.

OK, I can understand that but the problem is there are currently no
right options for the daemon to fix this.

> Rsync currently supports the full preservation of attributes in an
> incremental-backup scenario by copying into an empty hierarchy of files
> using one of the --*-dest options (usually --link-dest).  Anything
> different is a method of copying that rsync does not currently support
> (without an extra patch that adds an additional option).  It's not that
> unreasonable to want to do this, but at the moment if you're using link-
> dest into a directory of existing files, you're telling rsync that you
> care more about disk space and less about the history of file
> attributes (which is a choice that some folks have made when doing
> this).

I'm not advocating using "--link-dest" in a populated directory. I'm not
advocating using "--link-dest" at all.

The reason I wanted the default changed is because it would
automatically fix current backup systems that are vulnerable to this
problem without all the vulnerable folks out there having to update all
of their software and settings (just the rsync binary). Truly, though,
it's not really a problem in rsync but in the backup systems that made
the assumption that rsync's default behavior is appropriate for the job
they are giving it.

If the default won't be changed then it would be good to at least have
an option that can be mandated on the server (daemon) side to not tweak
attributes. That way maintainers of existing backup software can fix it
if they choose. Not the painless fix that changing the default would be
but at least something to reduce this vulnerability in what is probably
the most common usage of rsync.

> ..wayne..

Thanks,
Carl Thompson