Re: [Bug-tar] xattr support on Linux

[Tim Kientzle]

On Oct 4, 2012, at 8:45 AM, Joerg Schilling wrote:

> Tim Kientzle <address@hidden> wrote:
> 
>> 
>> On Oct 3, 2012, at 5:01 AM, Pavel Raiskup wrote:
>> 
>>>> FWIW, both star and bsdtar support xattrs on Linux.
>>>> 
>>>> It would be nice if GNU tar were compatible with those existing
>>>> implementations.
>>> 
>>> Thanks Tim, yes -- xattr-patched GNU tar would be unable to extract
>>> extended attributes from archives created by BSD tar now.  In BSD tar
>>> pax headers you are using base64 encoding for xattr values *but* in
>>> different namespace --> so it will be very easy to allow GNU tar unpack
>>> also BSD tar archives.  I missed that fact and I'll address that later.
>> 
>> Thanks!
>> 
>> bsdtar also URL encodes the xattr name when building the pax property
>> name.  This ensures the final key will be entirely ASCII (and hence will
>> not cause any problems with readers that expect all keys to be valid UTF-8).
>> 
>> I can point you to the code in libarchive that handles this if you want
>> a detailed reference.  (The code is BSD-licensed; you're welcome
>> to copy it if you wish.)
> 
> Mmm, is bsdtar incompatible to star?
> 
> Do you have a documentation for your format?

https://github.com/libarchive/libarchive/wiki/TarExtendedAttributes

As mentioned there, I'm also missing documentation for
star's xattr format.  In particular, I'm not clear how it handles
non-ASCII bytes in the attributes name.

I would appreciate help extending this documentation.
I've also tried to collect information about other tar
extensions.

Tim