Subject: Re: FYI: upgrading GNU tar
To: Takahiro Kambe <>
From: Giles Lean <>
List: current-users
Date: 10/14/2002 14:35:28
Takahiro Kambe writes:

> I'm writing now with my memory.  GNU tar is extended to handle longer
> path name; traditional tar was 100 bytes and cpio was 128 bytes.
> Dose IEEE 1003.2's pax support longer file names?

pax uses either tar or cpio formats.  The tar format has the historic
limitations.  The overall length for tar is 255 or 246, but the path
is stored in two places in the path header and must be split on a '/'
which leads to problems with very long filenames even within the
overall path limit.

I never remember what the limit is for cpio format, but its on-tape
format (at least for pathnames) is saner than tar's.

The on-tape format for both cpio and tar is documented in the pax(1)
standard, which is available somewhere on the web
site.  (I'd give complete URLs, but they keep moving things around.)

Alex Barclay wrote:

> It just completely boggles my mind that _ANY_ archiver would support 
> less than _POSIX_PATH_MAX. I've just had this problem recently trying to 
> dump a HP-UX 11.11 system. The system tar fouled up miserably with long 
> pathnames. When I used gtar everything was just fine.

... and what you wrote is not a portable tar archive, so you'll need
GNU tar to recover it, I expect.  Breaking at backup time rather than
recovery time could be considered a feature: that way at least you
know what you're dealing with while you have the data on-disk and can
decide what to do about it.