[Dar-support] Par2 not available on Ubuntu 20.04

[<sm8...@wi...>]

Am 08.07.22 um 20:38 schrieb Denis Corbin:
> Le 08/07/2022 à 12:51, Per Jensen via Dar-support a écrit :
>> I am using the par2 functionality with dar. If you are interested, take
>> a look at my github repo:
>>
>> https://github.com/per2jensen/dar-backup
Thanks, Per! In fact, I had already noticed your repo and glanced over 
it. The problem at hand seems to be very basic, though.
>> Now I owe you some explanations of what the problem is, the possible
>> solutions and a workaround:
>>
>> Den 08.07.2022 kl. 11.30 skrev sm8...@wi...:
>>> I have studied the documentation of Dar and wanted to start off with a
>>> first full backup with redundancy provided by Par2.
>>>
>>> However, the a command like
>>> dar --create INIT --fs-root=/tmp par2
>>> results in the error message
>>> Parse error: Given user target(s) could not be found: par2
>>>
>>> This happens on Ubuntu 20.04 with the packages dar (version 2.6.8) and
>>> par2 (version 0.8.1) installed and /etc/darrc containing the lines
>>> par2:
>>>      -B "/usr/share/doc/dar/examples/dar_par.dcf"
>>> and the file /usr/share/doc/dar/examples/dar_par.dcf
>>> containing the lines
>>> create:
>>>            -E '/usr/share/dar/samples/dar_par_create.duc "%p" "%b" 
>>> %N %e %c 2'
>>> test:
>>>            -E '/usr/share/dar/samples/dar_par_test.duc "%p" "%b" %N 
>>> %e %c'
>>>
>>> However, the folder /usr/share/dar is empty, and even manually copying
>>> the files* dar_par_create.duc and dar_par_test.duc from the source
>>> tar-ball into a sub-folder named samples (* made executable) did not do
>>> the trick.
> Well, they do not need to be executable, just readable by the user that
> is running the dar program.
>
>
> When using dar from source, the ./configure script that you run at
> first, has many options to define where should go the different results
> of the compilation as well as the documentation. These are the
> --prefix=<path> --bindir=<path> --sbindir=<path> --libexecdir=<path>
> --sysconfdir=<path> and other options passed to ./configure script.
>
> by default all goes in /usr/local, but when dar is provided from a
> distro package, it makes sense to use --prefix=/usr --sysconfdir=/etc,
> this is something that the distro maintainer for dar at Ubuntu 
> probably did.
>
> in that context the darrc file goes to /etc/darrc and the DCF files
> referred by /etc/darrc for par2 (dar_par.dcf file) goes to
> /usr/share/dar/samples. This dar_par.dcf file in turns relies on
> different DUC files also installed in that same directory
> /usr/share/dar/samples.
>
> During the installation, the dar source package modifies all these files
> content for the path to be correct in regard of the location of the
> referred files. It then works flawlessly.
>
> However here, it seems that the Ubuntu process does not only rely on the
> ./configure options to set the destination paths, but also manually
> moved the dar_par.dcf file from "/usr/share/dar/samples" to
> "/usr/share/doc/dar/examples". If they modified the /etc/darrc to
> reflect this change, they missed to modify the content of dar_par.dcf
> file to reflect the new location of the DUC files it refers.
>
> note also that "samples" has been renamed "examples" so you need to
> change this also in dar_par.dcf, probably the reason why you could not
> have it working?
Thanks for this extensive answer, Denis! It is in fact the way you 
suspect. Indeed, all files are under /usr/share/doc/dar/examples/.
>
>>> Is this a known problem with a solution? I have tried searching the
>>> mailing list archives but the key "par2 target not found" returns 
>>> almost
>>> 4'000 pages dating back to the year 2002 and the first one containing
>>> "par2" in the title is from 2013; similar for "parchive" instead of
>>> "par2". I gave up and am hoping for some support from the list members.
> In other words I suspect the duc files are also in
> /usr/share/doc/dar/examples beside the dar_par.dcf file. Just modifying
> the dar_par.dcf replacing...
>    /usr/share/dar/samples
> by
>    /usr/share/doc/dar/examples
>
> ...should make it working. Can you test that? (pay attention to
> "samples" vs "examples" in the path)
>
> This was for a workaround. For a real fix, you should contact the person
> in charge of dar/libdar packaging at Ubuntu to have this fixed. I'm also
> flexible on my side, if 'examples' makes more sense than 'samples' this
> can be changed in the dar source code.

No luck, unfortunately. I did change the paths in dar_par.dcf:
create:
         -E '/usr/share/doc/dar/examples/dar_par_create.duc "%p" "%b" %N 
%e %c 2'
test:
         -E '/usr/share/doc/dar/examples/dar_par_test.duc "%p" "%b" %N 
%e %c'

Nevertheless, I still get
Parse error: Given user target(s) could not be found: par2
... upon launching
dar --create INIT --fs-root=~/.config par2

Is there anything obvious that I am missing? Thanks in advance for any 
advice!

Stefan Mueller