Re: Getting "Skipping backward is not possible on a pipe" after upgrade

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On 19/10/2019 00:34, Vladimir Mosgalin wrote:
> Hi Denis Corbin!
> 
> On 2019.10.18 at 21:06:05 +0200, Denis Corbin wrote next:
> 

[...]

> 
> I am using compression, and retry-on-change option is enabled by
> default: --compression=xz:3 -m 256 --cache-directory-tagging 
> --alter=secu
> 
> also some things like compression excludes.
> 
> Still, this worked in the past; I remember rare warnings like
> "file keeps changing, stop trying to backup new copies" (from
> default retry-on-change value of 3) and it did not prevent this
> pipe thing from working.
> 
>> anyway, putting appart the third case, before skipping backward
>> dar tests whether it is possible to skip backward. If not it
>> flags file as dirty or keep it with a bad compression ratio.
>> 
>> So this is probably a bug, I will chase it
> 
> Thanks!

bug found and fixed in 2.6.7.RC3 which will become 2.6.7 in a few weeks.
You can grab the source code on GIT or use the tarball available at
ftp://ftp.dm3c.org/dar.linux.free.fr/Interim_releases

> 

[...]

> 
>> simple no? ;-)
> 
> Actually, to be completely honest - no :) Some parts of dar syntax
> and especially things like its interaction with piping, dar_xform
> and few others are just so complicated both in concepts and syntax
> (even comparing to lots of other complicated features, many of
> which I use!) so I try to avoid them.
> 
> Frankly I find dar to have too many options and many of them to be
> too complex - that is, actually accessing its features is too hard
> sometimes.


I can hear that some features are not accessible or not well designed,
there is still room for improvement and I thank you for your
franckness and feedback ;-)

> 
> For me it's dar #1 shortcoming (#2 being lack of multithreaded 
> compression support.. even though things like xz -T, pigz and
> pbzip2 work nice, but dar is usually limited by single cpu core
> doing compression).

I lack a portable library that implement parallel compression
algorithms... I will have to implement it myself, but this is not at
the top of my TODO list

> Then again, each time I think that it's too complicated and want to
> replace it with something else when wanting to back up some new
> computer, I discover that I just can't find another tool which
> does the same - full and differential backup to single archive with
> splitting by size, compression, excludes that can be used from
> command line in non-interactive way. So I even started to backup
> some Windows systems with dar because... I checked reviews of like
> "25 best backup tools for Windows" and they all lack this simple
> set of features :)

:)

> 
> So, this huge set of features also means that everyone can find
> whatever they need. Which is very nice :) Thanks again for this
> tool, it's awesome.

Thanks,

> 
> Oh yeah, #3 dar shortcoming for me is exactly this, problematic 
> interaction when wanting to backup one system while storing backup
> on the other. So far, netcat is the only solution I know but it's
> far from elegant..
> 

Regards,
Denis
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