+
+ This has been reported as conflicting with the POSIX specs. The reason is
+ that offsets and sizes of non-zero data blocks were stored in multiple
+ instances of GNU.sparse.offset/GNU.sparse.numbytes variables, whereas
+ POSIX requires the latest occurrence of the variable to override all
+ previous occurrences.
+
+ To avoid this incompatibility two following versions were introduced.
+
+ * 0.1
+
+ Used by tar 1.15.2 -- 1.15.91 (alpha releases).
+
+ The sparse file map is stored in
+ x header:
+
+ GNU.sparse.size Real size of the stored file
+ GNU.sparse.numblocks Number of blocks in the sparse map
+ GNU.sparse.map Map of non-null data chunks. A string consisting
+ of comma-separated values "offset,size[,offset,size]..."
+
+ The resulting GNU.sparse.map string can be *very* long. While POSIX does not
+ impose any limit on the length of a x header variable, this can confuse some
+ tars.
+
+ * 1.0
+
+ Starting from this version, the exact sparse format version is specified
+ explicitely in the header using the following variables:
+
+ GNU.sparse.major Major version
+ GNU.sparse.minor Minor version
+
+ X header keeps the following variables:
+
+ GNU.sparse.name Real file name of the sparse file
+ GNU.sparse.realsize Real size of the stored file (corresponds to the old
+ GNU.sparse.size variable)
+
+ The name field of the ustar header is constructed using the pattern
+ "%d/GNUSparseFile.%p/%f".
+
+ The sparse map itself is stored in the file data block, preceding the actual
+ file data. It consists of a series of octal numbers of arbitrary length,
+ delimited by newlines. The map is padded with nulls to the nearest block
+ boundary.
+
+ The first number gives the number of entries in the map. Following are map
+ entries, each one consisting of two numbers giving the offset and size of
+ the data block it describes.
+
+ The format is designed in such a way that non-posix aware tars and tars not
+ supporting GNU.sparse.* keywords will extract each sparse file in its
+ condensed form with the file map attached and will place it into a separate
+ directory. Then, using a simple program it would be possible to expand the
+ file to its original form even without GNU tar.
+
+ Bu default, v.1.0 archives are created. To use other formats,
+ --sparse-version option is provided. Additionally, v.0.0 can be obtained
+ by deleting GNU.sparse.map from 0.1 format: --sparse-version 0.1
+ --pax-option delete=GNU.sparse.map