"Garrett D'Amore" <Garrett.Damore at sun.com> wrote:
> 1) Given that this requires new flags to be added (as well as creates a
> new file format), is there a compelling reason to add these flags rather
> than just telling folks who want holey file support to use pax? (I
> guess this is a level 0 question... it seems like pax does everything
> cpio does, only more?)
According to the man page, Sun pax does not support sparse files.
> 4) Is there any other convention or standard for holey cpio archives in
> common use? (E.g. something supported by Linux or star?)
The cpio archive formats (there are at least 3 completely incompatible cpio
archive formats) in general are hard to extend. This was the main reason for
POSIX to give up cpio based formats for future archive formats. The older
cpio formats are limited to a max. file size of 8 GB, the SVr4 based formats
are limited to 4 GB per file.
Star supports sparse files in tar based archives and tar based archives are
also used for the POSIX.1-2001 extended archive format.
If you like to implement things like sparse files, you in general need to take
specific care about implementation details of the archivers. While it is easy
to implement many things in simple archivers like Sun tar, Sun pax, Sun cpio or
GNU tar, it may be hard or slow to implement the same in a fully buffered
archiver implementation like star.
For this reason, I designed all star extensions in a way that no data spans
over
more than one 512 byte data block. The current archive format proposal does not
follow this rule.
J?rg
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