From: Bruce Momjian <bruce@momjian.us>
Message-Id: <200705140104.l4E14rn21632@momjian.us>
Subject: Re: [GENERAL] PITR and tar
In-Reply-To: <20070513224408.GC69517@nasby.net>
To: "Jim C. Nasby" <decibel@decibel.org>
Date: Sun, 13 May 2007 21:04:53 -0400 (EDT)
CC: Jeff Davis <pgsql@j-davis.com>, Dhaval Shah <dhaval.shah.m@gmail.com>,
	pgsql-docs@postgresql.org, Tom Lane <tgl@sss.pgh.pa.us>
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset="US-ASCII"

Jim C. Nasby wrote:
> Moving to -docs...
> 
> Does anyone know what the history of the docs saying that GNU tar had
> issues with files changing underneath it? According to this report it's
> actually BSD tar that has the issue.

As I remember, Tom was the one who found that GNU tar would return a
non-zero exit status if the file changed during backup, so you couldn't
determine if the backup was successful based on the exit code.

---------------------------------------------------------------------------


> 
> On Wed, May 09, 2007 at 10:19:05AM -0700, Jeff Davis wrote:
> > On Wed, 2007-05-09 at 11:40 -0500, Jim Nasby wrote:
> > > Actually, looking at the docs, the problem is with some versions of  
> > > GNU tar. AFAIK bsdtar is perfectly happy to archive files that have  
> > > changed from underneath it.
> > > 
> > 
> > $ tar --version
> > bsdtar 1.2.53 - libarchive 1.3.1
> > 
> > That fails to create a file in proper gzip format when the files are
> > concurrently modified.
> > 
> > However, 
> > 
> > $ tar --version
> > tar (GNU tar) 1.14
> > Copyright (C) 2004 Free Software Foundation, Inc.
> > This program comes with NO WARRANTY, to the extent permitted by law.
> > You may redistribute it under the terms of the GNU General Public
> > License;
> > see the file named COPYING for details.
> > Written by John Gilmore and Jay Fenlason.
> > 
> > That _appears_ to work.
> > 
> > Perhaps FreeBSD users should take notice of this problem. It's certainly
> > not a postgresql problem, but I know there are a lot of freebsd users
> > here, and using tar on fast-changing data may be rare outside of
> > postgresql.
> > 
> > Regards,
> > 	Jeff Davis
> > 
> 
> -- 
> Jim Nasby                                      decibel@decibel.org
> EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Have you searched our list archives?
> 
>                http://archives.postgresql.org/

-- 
  Bruce Momjian  <bruce@momjian.us>          http://momjian.us
  EnterpriseDB                               http://www.enterprisedb.com

  + If your life is a hard drive, Christ can be your backup. +