Description
The pax header block is identical to the USTAR header
block described in tar — Format of tar archives, except that two additional
typeflag values are defined:
- x
- Represents extended header records for the following file in
the archive (which shall have its own USTAR header block). The format
of these extended header records shall be as described in pax extended header.
- g
- Represents global extended header records for the following
files in the archive. The format of these extended header records
shall be as described in pax extended header. Each value shall affect
all subsequent files that do not override that value in their own
extended header record and until another global extended header record
is reached that provides another value for the same field. The typeflag g global
headers should not be used with interchange media that could suffer
partial data loss in transporting the archive.
For both of these types, the size field shall be the size of
the extended header records in octets. The other fields in the header
block are not meaningful to this version of the
pax utility.
However, if this archive is read by a
pax utility conforming
to the ISOPOSIX-2:1993 standard, the header block fields are used
to create a regular file that contains the extended header records
as data. Therefore, header block field values should be selected to
provide reasonable file access to this regular file.
A further difference from the USTAR header block is that data blocks
for files of typeflag 1 (the digit one) (hard link) might be included,
which means that the size field may be greater than zero. Archives
created by pax -o linkdata shall include these data blocks
with the hard links.