Re: [Duplicity-talk] checksum rsync option (duplicity 0.6.21)

[edgar . soldin]

On 22.07.2013 17:11, Laurent Lavaud wrote:
> ok thanks for the explanations, i can remove my useless rsync option !
> 
> and i have found the guilty option in my tag tool (puddletag), "preserve file 
> modification time", it is weird to add an option like this...
> 
> 
> --
> Laurent Lavaud
> Administrateur Systèmes et Réseaux
> 
> ----- Mail original -----
>> On 22.07.2013 14:23, Laurent Lavaud wrote:
>>> Hello,
>>>
>>> I would like to use the rsync checksum method to detect files
>>> modification because the "classic" method do not detect some
>>> changes, like mp3 tag modification (mtime not modified)
>>>
>>> So i have tried to add --rsync-options="--checksum" to my duplicity
>>> command line:
>>>
>>> /usr/bin/duplicity -v9 --encrypt-key=xxx --sign-key=xxx --use-agent
>>> --allow-source-mismatch --rsync-options="--checksum" test
>>> ssh://address@hidden/backup/test
>>>
>>> But duplicity doesnt seem to use it because it not detect the file
>>> modification...
>>>
>>
>>
>> --rsync-options only applies to the rsync backend. the internal
>> librsync routine is not configurable. actually duplicity itself
>> decides if the file changed and invokes librsync internally then.
>>
>> duplicity compares wrt. time only mtime
>>  
>> http://bazaar.launchpad.net/~duplicity-team/duplicity/0.6-series/view/head:/duplicity/path.py#L306
>> for performance reasons.
>>
>> only verify can compare data as well. this is a design decision.
>> duplicity backup data is usually stored remotely. comparing data
>> during backup would need to restore the former version of the file
>> locally and therefor download all volumes necessary resulting in
>> lot's of traffic.
>>
>> what i describe above is merely the status quo. i am aware that in
>> theory a checksum could be saved remotely but i cannot find anything
>> like that in duplicity's source. the tarfile info used as metadata
>> store also does not seem to support an entry like that.
>>
>> Ken, Mike: is the above correct?
>>
>> Laurent: wrt. your issue above. the behaviour of your tagging
>> software or filesystem is the "real" problem here. usually
>> filesystems modify mtime automatically on every write access. if
>> not, something weird is going on and you should research what's
>> going on there. e.g. we had users on the list where mounted remote
>> filesystems did not update file stat data correctly.
>>
>> good luck ..ede/duply.net
>>
>>
>>
>>
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