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Date:      Thu, 19 Apr 2018 22:00:13 -0600
From:      Gary Aitken <freebsd@dreamchaser.org>
To:        Polytropon <freebsd@edvax.de>
Cc:        FreeBSD Mailing List <freebsd-questions@freebsd.org>
Subject:   Re: tar xf foo -- how to restore symlink?
Message-ID:  <9e435ffd-8997-74c7-9502-854a004ac5cc@dreamchaser.org>
In-Reply-To: <20180419160503.38e1aa75.freebsd@edvax.de>
References:  <5ff313cf-6148-be90-0195-7d21f1f836ac@dreamchaser.org> <20180418063005.056e321d.freebsd@edvax.de> <9902b54d-4684-6ba6-a08b-f3d9504c1273@dreamchaser.org> <20180419160503.38e1aa75.freebsd@edvax.de>

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On 04/19/18 08:05, Polytropon wrote:
> On Wed, 18 Apr 2018 20:20:30 -0600, Gary Aitken wrote:
>> On 04/17/18 22:30, Polytropon wrote:
>>> On Tue, 17 Apr 2018 22:20:23 -0600, Gary Aitken wrote:
>>>> I've got a tarball with an archived symlink and its contents. The
>>>> symlink points to another directory in the tarball, and the tarball
>>>> contains copies of the files in the symlinked directory.
>>>>
>>>> A normal extract fails with the message: $ tar -xf
>>>> nufraw-0.41.tar.gz nufraw-0.41/doc-pak: Can't replace existing
>>>> directory with non-directory
>>>>
>>>> What's the right way to deal with this?
>>>>
>>>> How do I get tar to restore the symlink as a symlink? -k and
>>>> --exclude allow tar to continue unpacking, but don't restore the
>>>> symlink as such.
>>>>
>>>> "man tar" doesn't seem to have what I want but I'm probably blind.
>>>
>>> Have you checked if -P or -U result in the intended behaviour?
>>
>> no, they didn't seem appropriate
>>
>>> -P, --absolute-paths Preserve pathnames.  By default, absolute
>>> pathnames (those that begin with a / character) have the leading
>>> slash removed both when creating archives and extracting from them.
>>> Also, tar will refuse to extract archive entries whose pathnames
>>> contain .. or whose target directory would be altered by a symlink.
>>> This option suppresses these behaviors.
>>
>> The archive is relative, not absolute
>>
>>> -U, --unlink, --unlink-first (x mode only) Unlink files before
>>> creating them.  This can be a minor performance optimization if most
>>> files already exist, but can make things slower if most files do not
>>> already exist.  This flag also causes tar to remove intervening
>>> directory symlinks instead of reporting an error.  See the SECURITY
>>> section below for more details.
>>
>> Creates duplicate directories, rather than a symlink.
>>
>>> Check "man tar" for "symlink". :-)
>>
>> Did that, didn't find anything useful.
>> But then I don't always read so well, much less comprehend...
>> That's why I asked :-)
> 
> Sadly, I do not remember anything specific to help you with tar,
> but I do remember that cpio has the feature you are searching for.
> I've been using it probably for exactly that purpose: because it
> keeps "special entries" in file system hierarchies when restoring
> from the archive.
> 
>>From "man cpio":
> 
>       -L      (o and p modes) All symbolic links will be followed.  Normally,
>               symbolic links are archived and copied as symbolic links.  With
>               this option, the target of the link will be archived or copied
>               instead.
> 
> Maybe if you try to transfer the data in question with cpio,
> you can achieve the result you are expecting?

Unfortunately, I'm not in control of generating the archive or the way
it's fetched.  It's fetched via the ports system.  I'm going to punt on
the project for now as I've got a better alternative.

Thanks,

Gary



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