PIF spec:  http://www.opengroup.org/onlinepubs/009695399/utilities/pax.html#tag_04_100_13_02
(same place for all Pax specs).


Command-line syntax is a merge between tar and cpio.

CREATE ARCHIVE:

    pax [-x format] -w dir/path file/path > file.tar
    Format defaults to "ustar".

LISTING
    pax < file.tar


CONFORMANCE
Writes the ustar magic name and version according to POSIX ustar spec.
Terminates header checksum like a regular tar number instead of with space
 also, according to tar spec.
By defaults writes the additional ustar values:
    Device major number: all 0's
    Device minor number: all 0's

Pax writes additional tar file entries of ustar format "x" or "g".
I glean that x impacts Next entry; g applies all following entries.
"g" is apparently not well supported.
These have file contents formatted according to Pax Interchange Format.


Pax Interchange Format
I SEE NO WAY TO CAUSE Linux or Solaris "pax" IMPLEMENTATIONS TO WRITE A PIF.
 (Maybe it would do so automatically if the filename > length of "name" +
 "prefix" fields, if of file size > 8G?).
According to http://www.opengroup.org/onlinepubs/009695399/utilities/pax.html ,
(2004 spec?) this requires "-x pax", but the very latest 2008 "pax"
implementations for Linux and Solaris don't support "-x pax".
But, according to info:/tar, you can use
The PIF headers contain funny name.  According to info:/tar, defaults to
/path/to/dir/PaxHeaders.1234/file.name
I.e., it takes specified file name and inserts "PaxHeaders.<PID>".
FOR NOW, FUCK "pax".  Use "tar --format=posix" to write PIFs.  Gives by default:
    UStar major and minor devices all 0's.
    PIF file containing just atime and ctime settings
     (these signify access and inode change times, respectively).
GNU tar does not automatically use PIF for large files.  It probably uses
 binary number extension.  Must use --format=posix to get PIF with GNU tar.