[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Tar question -- star is recommended until GNU Tar 1.14 is

On Thu, 2004-08-05 at 22:58, Erich Schroeder wrote:
> Sort of answered my own question. I downloaded and install star:
> http://www.fokus.gmd.de/research/cc/glone/employees/joerg.schilling/private/star.html
> an enhanced version of tar

It's not really an "enhanced version of tar" but a more _POSIX_
compliant version.  That's why it has been a part of Fedora Core (FC)
since version 0.8* and _recommended_over_ GNU Tar 1.13.

Understand that cpio, tar and, their new replacement, pax, just write
what is known as "ustar" format.  The latest IEEE POSIX 2001 and X/Open
Single Unix Specification (SUS) 3 from the "Austin Group" defines a lot
of new functionality that really makes up for lack of capability in the
older 1988 and subsequent releases until the late '90s drafts.

This includes overcoming POSIX 1988+ path/naming limitations, as well as
newer POSIX 2001 capabilities like storing POSIX EA/ACLs.

In the meanwhile, the GNU maintainers decided to release their own
extensions that are not compliant.  It was a necessary evil, but now
that the POSIX/SUS standard has been updated, it's time for GNU to come
around.  The current GNU Tar 1.14 alpha adds these capabilities.

star actually had EA/ACLs support on Solaris** _before_ the POSIX
standardization, so adopting it for POSIX 2001 / SUS 3 ustar meta-data
format was easy.

Unfortunately POSIX 2001 / SUS 3 still does _not_ address the issue of
compression.  I hate the idea of block compressing the entire archive,
which renders it largely unrecoverable after a single byte error (at
least with LZ77/gzip or LZO/lzop -- BWT/bzip2 may be better at recovery
though).  That's my "beef" with the whole ustar format in general.

I would have really liked a flexible per-file compression meta-data tag
in the standard.  Until then, we have aging cpio replacements like afio.

-- Bryan

*NOTE:  This is the actual "disttag" versioning (i.e., technical
reasons) for pre-Fedora Core "community Linux" releases from Red Hat
that are now recommended for Fedora Legacy support (i.e., FC 0.8 is fka
"RHL" 8), in addition to any relevant trademark (i.e., non-technical)

**NOTE:   legacy star used Sun's tar approach -- an ACL "attribute file"
preceding the data file, but using the same name.  That way if the tar
program extracting it was "Sun EA/ACL aware," it would read it, but if
not, it would just overwrite the attribute file with the actual when
extracted.  Quite ingenious of an approach.

Engineers scoff at me because I have IT certifications
 IT Pros scoff at me because I am a degreed engineer
    I see and understand both of their viewpoints
  Unfortunately Engineers and IT Pros only see in me
       what they dislike about the other trade
Bryan J. Smith                      b.j.smith@ieee.org

To unsubscribe, send email to majordomo@luci.org with
"unsubscribe luci-discuss" in the body.