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[Bug-tar] Errors in "posix" format.
From: |
Tim Kientzle |
Subject: |
[Bug-tar] Errors in "posix" format. |
Date: |
Sun, 25 Jul 2004 19:20:15 -0700 |
User-agent: |
Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.4) Gecko/20031006 |
I've been doing some interoperability testing between bsdtar
and gtar's newly-implemented "posix" format and I have a few quibbles:
* No user/group stored with 'x' entry.
If the archive is extracted by a reader that
doesn't understand pax extended attributes,
then the 'x' entry is supposed to be treated
as a regular file. (According to POSIX, since
about 1987.) It's therefore important that the
'x' entry have basic permission and ownership
attributes set correctly.
* Poor naming of 'x' entry. Long filenames get
truncated at 100 characters. Following the logic
above, this could result in readers overwriting
other files with the contents of 'x' entries.
* No size stored in main entry if file size exceeds
8gig. Readers that don't support pax extended attributes
rely on the file size to locate the next entry.
It is quite appropriate to use numeric extensions
(e.g., base-256) here. Compliant readers should
ignore the value (in favor of the value stored in the
extended attribute entry), so it does not compromise
standards compliance, but does help ensure that
the widest possible array of readers can extract
the file (such as GNU tar 1.13 ;-).
Finally, I find the name "posix" for this format to
be quite misleading; some people will think you're referring
to "ustar" which is also a POSIX format. The official
name of this format in the Single Unix Standard is "pax extended."
For reference, you might take a close look at two other open-source
archivers that implement this format: star refers to this format
as "xustar" (extended ustar) and bsdtar refers to this as "pax".
Tim Kientzle
- [Bug-tar] Errors in "posix" format.,
Tim Kientzle <=