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Re: [Bug-tar] Filesystem detection

From: Doug McLaren
Subject: Re: [Bug-tar] Filesystem detection
Date: Thu, 1 Sep 2011 15:45:20 -0500
User-agent: Mutt/1.5.21 (2010-09-15)

On Wed, Aug 31, 2011 at 05:27:15PM -0700, Paul Eggert wrote:

| On 08/31/11 07:21, Ederson Ferreira wrote:
| > I think you can reproduce it as follows:
| > 
| >    1. pack a large bunch of files (~100Gb) in a tar ball using tar version 
1.15.1 on a 64-bit machine
| >    2. unpack the tar ball in a 32 bit machine using a more recent version 
(I used version 1.22, shipped with Ubuntu Server 10.04)
| > 
| > If you have the same problem as I did, in some random file during the 
extraction that error message would rise, stopping the execution.
| > 
| > I only detected the problem when I installed version 1.15.1 of tar, that 
raise a different error message: tar file contains obsolete base-64 headers. 
After trying on a 64-bit machine, everything gone well.

As Paul said earlier, tar's output format should not vary from
architecture to architecture.  Because of this, I'd expect that any
archive that was created on one box that can't be opened on another
box to be corrupt -- and probably couldn't be opened on the first box

As for a recipe, I'd suggest giving the exact tar command used to
create the tar archive, and the exact command used to try to read it.
Also, I'd suggest getting ...

   "tar --version" output on both boxes

   "tar --help" output on both boxes  { it gives the default options }

   The first few KB of the unreadable tar file created (don't email a
   100 GB file to somebody, but a few KB file ought to be OK.  I'm not
   sure if the list will accept mime attachments, but you could upload
   it somewhere and provide a link.)

Also, does it happen if you use small files rather than 100 GB worth
of files?

You might also want to try getting md5sums of the tar file right after
creation, and then get it again when you try to untar it, just to make
sure the file hasn't changed.

| Possibly the bug is already fixed in the latest version of gnu tar.

Sounds like a really serious bug.  So serious that lots of people
would have problems with it.  My guess is that it's not a bug in tar,
but something else (usage error, system problems, etc.)  Or if it is a
bug in tar, it's with some rarely used options.  But of course that's
just a guess.

Doug McLaren, address@hidden
They who say cannot be done should not interfere with those doing it.

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