Re: [Duplicity-talk] Tarfile support

[Rob Browning]

Ben Escoto <address@hidden> writes:

> But a longer term problem is that GNU tar isn't a very good format,
> and I recently emailed and it wasn't clear when/if they were going to
> add ACL/EA support.  I think the format that an archiver like star
> uses is more standards compliant and better in other ways also.
>
> I guess I haven't really asked a question, but comments on this issue
> are welcome.

What are the alternatives?  For example, what are the limits on afio
archives?  I seem to recall that afio might try to to better than
cpio, but I don't know how much better.  Also, does star fix the (age
old) issues with hard links, filename lengths, etc?  From briefly
looking at star's documentation, it *sounds* like it's better than gnu
tar, though it still has a 1024 byte path limit.

I briefly wondered if it might be possible (and not completely crazy)
to try creating a simple duplicity specific format.  If ar, tar, or
similar had enough minimum functionality across platforms, perhaps you
could just write 2 files to the archive per real file, one with the
file metadata, and the second with the file data.  The metadata file
would also contain the file's real (long) name, etc.  This should
allow you could accomodate arbitrary filename lengths, have smarter
hard-link handling, etc.

However, after thinking about it, being able to collect (and restore)
the metadata portably sounds like a moderately hard problem (though I
suppose perhaps you could build on existing code), and you would also
end up with the very serious responsibility of making sure your
archive/unarchive code was *absolutely correct*.

-- 
Rob Browning
rlb @defaultvalue.org, @linuxdevel.com, and @debian.org
Previously @cs.utexas.edu
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