Re: dar -d -- diff of file data or metadata?

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On Tue, 30 Mar 2021 21:35:11 +0200
Denis Corbin <[email protected]> wrote:
> On 30/03/2021 01:39, David Niklas wrote:
<snip>
> > 
> > Please tell me which way it is. And perhaps clarify it inside of the
> > man page.  
> 
> Note that in the context of differential and incremental backups, dar
> will check file's metadata only to decide whether a file has changed
> since the backup of reference was made. If data corruption occurred
> inside the data only (leaving untouched the metadata), the corrupted
> version of the file will not be saved by dar (unless file has been
> created after the backup of reference).
> 
> In that context, comparing a differential backup with a filesystem (-d
> option), let dar check what is in the backup, if the file had not
> changed, only its metadata is present and thus possible to compare to
> the live (possibly corrupted) filesystem. Thus, a data corruption
> affecting a file's data (not its metadata) is impossible to detect and
> report, and the funny thing is that your backup are more sane than your
> filesystem, while not wasting your backup storage with corrupted data.
> 
> I hope this can bring some light to the behavior you have observed,
> while nothing tells this is what succeeded, this is just a very probable
> hypothesis.
> 
<snip>

I was performing a differential backup so that explains dar's behavior.
Thanks again,
David
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