[Duplicity-talk] Re: Help me replace tar!

[Ben Escoto]

On Fri, 17 Oct 2003 15:21:16 +0200 (CEST)
Joerg Schilling <address@hidden> wrote:
> THE way to go for an archiver is to use the extensible POSIX.1-2001
>> format.  Star is the first tar implementation for the POSIX.1-2001
>> tar format aka. PAX.  During the last two years, star did add a lot
>> of features based on POSIX.1-2001 extensions. This allows star to
>> implement things that other tar implementations cannot do.

Ok, I'm starting to understand a bit better now.  So star complies
with the SUSv3 description of pax?  (There does not seem to be any
entry for "tar" itself.)  Then what is the status of the pax utility
that I seem to have on my system, but never use?  And why is your
project named "star" instead of "spax"?  (Aesthetic considerations
aside of course :-))

> Are you sure? I don't know any description of the archive format
> used by GNU tar. All I could do when implementing GNU tar
> compatibility inside star was to read the GNU tar source and check
> the behavior :-( .... This is why I know that GNU tar is full of
> bugs.

Well, I'm referring to pages such as:

http://www.gnu.org/manual/tar/html_node/tar_123.html#SEC118

You are right that GNU tar doesn't always seem to follow that
precisely (in fact an issue arose about this a few days ago with large
uids), but the manual seems approximately accurate and much better
than nothing.

> The POSIX standard is at the Open Group. Go to www.opengroup.org and
> register for free html view of the SUSv3 standard. This has been
> taken as the POSIX.1-2001 by ISO.

This paragraph explains why I wasn't able to find a copy before:

    You are permitted to read the HTML and PDF versions of Open Group
    publications using your HTML browser/Acrobat software and to
    download them for your own personal use provided you have given
    your name and email address for each publication
    requested. However, you are NOT permitted to amend, copy, reprint,
    offer for sale, or otherwise re-use material from these documents
    without explicit permission from The Open Group.

What kind of standard doesn't allow people to distribute it??  This
seems worse than no standard at all, because at least with no
standard, you can write up a description of a project's intended
behavior.  With this kind of license that may become copyright
violation.

But anyway, I have downloaded the pax specification, and will read it
to see how suitable it is for duplicity.

> -     GNU tar is far from the POSIX archive standard, so if you move
>       to star, your machine may be used fine, but other people who
>       only have GNU tar may get into problems because GNU tar may
>       have problems to read even POSIX.1-1988 archives.

I see, GNU tar may be holding everything up.  Have you talked to them?
>From my brief interaction they don't seem to have too much time.
Maybe you could just get your project accepted by GNU as the new
version of GNU tar?  If that doesn't appeal to you, maybe you could
contribute just enough code to gnu tar so it doesn't barf on basic
star archives?


-- 
Ben Escoto

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