Re: show/compare compression algorithm/level

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On 24/06/2019 21:20, Matus UHLAR - fantomas wrote:
>>>> On 21/06/2019 19:53, Matus UHLAR - fantomas wrote:
>>>>> is it possible when listing dar archive to show the 
>>>>> compression algorithm and level used for files?
>>>>> 
>>>>> and when merging archives, e.g. creating decremental
>>>>> archive, does dar detect the same file even if it's
>>>>> compressed using different algorithm/level?
> 
>>> On 21.06.19 23:48, Denis Corbin wrote:
>>>> dar -l <archive> -q
>>>> 
>>>> will let you see the compression algorithm used, but not the 
>>>> compression level. For that you can use for example 
>>>> '--user-comment %c' at archive creation time (let you refer
>>>> to the man page for this option details) and see what was
>>>> the command line used to create the archive.
> 
>> On 23/06/2019 20:06, Matus UHLAR - fantomas wrote:
>>> so, only one compression scheme can be used per archive?
> 
> On 24.06.19 19:41, Denis Corbin wrote:
>> Yes for now: once a compression algorithm has been selected you
>> can define which file to compress and which file not to try
>> compressing.
>> 
>> The archive format has room to have compression algorithm and 
>> compression level per file, but so far this has not been founded
>> very useful.
>> 
>> What is your use case for such feature?
> 
> for now, I'm interested because I have tried to create different
> backups using different compression schemes (no big luck) and I was
> curious if it's possible to make decremental archive from them
> without recompression.
> 

I see. You are correct, building a decremental backup is specific
merging operation. As of today, merging is not able to keep file
compressed if the two archives have different compression algorithms.

I will raise the priority of this feature for it be part of 2.7.x
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