Re: Extattr portability?

From: Dylan Cochran <a134qaed_at_gmail.com>
Date: Sat, 10 Jan 2009 02:41:31 -0500
On Fri, Jan 9, 2009 at 10:27 AM, Robert Watson <rwatson_at_freebsd.org> wrote:
> On Wed, 7 Jan 2009, Tim Kientzle wrote:
>
>> I'm trying to complete the extended attribute support in libarchive.
>>  There are a handful of odd issues that arise which I think I could resolve
>> if I knew of good use cases.
>>
>> Anyone here actually use extended attributes?  (Note that ACLs are handled
>> separately.)  What software?  What information do you store there?
>>
>> If you could benefit from being able to move extended attributes between
>> FreeBSD and other systems, I'm especially interested.
>
> Most (all) of the use of extended attributes that I'm aware of on FreeBSD
> relates to security extensions, be it ACLs, MAC labels (almost always in the
> system namespace) for various policies, etc.  Mac OS X is now using extended
> attributes in quite a few more ways, however, so you may want to investigate
> a bit on that side.  Most uses I'm aware of aren't intended to be portable.

Another is BeOS/Haiku, which used attributes heavily. I have been
waiting for this work for a while. What I don't really mind is whether
it is portable, what I really care about is full retention of the user
namespace. No silent truncating of an attribute because of perceived
need for a size restriction, assuming the contents are only ASCII,
etc. If setextattr can set it on a file, tar should be able to retain
it as is, and extract it so getextattr later is identical. If that can
be done using an already defined extended attribute format, great! If
it can't, I can live with an incompatible tar format.

That's my 2 cents on the matter, I use extended attributes now for
storing cached mime-type, and sha256/md5 for checksum purposes. I have
plans sometime in the future to create a patch for ROX-Filer to check
for thumbnail and icon attributes, and use them instead of the current
cache scheme. Being able to tar up the directory, and then extract it
and keep the thumbnail/icon as expected, would greatly improve user
experience, in my opinion.
Received on Sat Jan 10 2009 - 07:08:36 UTC

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