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Subject:	=?UTF-8?Q?Re:_tar_incremental_backups_and_ctime=e2=80=8f_problem?=
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From:	Marco Atzeri <marco DOT atzeri AT gmail DOT com>
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Date:	Mon, 23 May 2016 17:35:20 +0200
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On 23/05/2016 16:57, x y wrote:
>> mtime is fakeable, ctime is not.  Using only mtime makes it likely that
>> your incremental backup will miss files.  I don't have any good reason
>> to differ from upstream behavior here.
>
> Hi Eric,
>
> The problem is not faking time stamps. Even commercial Windows backup
> programs are checking the modification time to identify the modified
> files.
>
> Consider that you have a lot of files opened and closed without any
> modification in your company. Because of the priority of the ctime
> time stamp, reintroducing all of those files to the incremental backup
> does not make any sense. tar has also the capacity to create
> differential backups with the condition of taking care of the snapshot
> file. The ctime issue can result in unnecessarily big differential
> backups filled with unmodified files.
>
> Cygwin tar can be a good  alternative for Windows users to do
> differential \ incremental backups but the ctime problem must be
> solved.
>

It is always possible to create file list with find and use that
to tar whatever using --files-from=FILE option

I don't see the need to change tar behaviour to meet your wish.

Regards
Marco








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