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Re: tar, but not gnu tar

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tena Sakai <tsakai(at)gallo(dot)ucsf(dot)edu>
Cc: pgsql-admin(at)postgresql(dot)org
Subject: Re: tar, but not gnu tar
Date: 2007-08-22 01:33:34
Message-ID: 200708220133.l7M1XYt15860@momjian.us (view raw or flat)
Thread:
Lists: pgsql-admin
Tena Sakai wrote:
> Hi Everybody,
> 
> According to section 23.3.2 of 8.2.4 manual:
> 
>   Also, some versions of GNU tar consider it
>   an error if a file is changed while tar is
>   copying it. There does not seem to be any
>   very convenient way to distinguish this
>   error from other types of errors, other
>   than manual inspection of tar's messages.
>   GNU tar is therefore not the best tool for
>   making base backups.
> 
> On my linux machine, gnu tar is the tar.  Does
> anybody have a suggestion as to where I can go
> to get a tar that is not gnu?

We have updated the 8.3 documentation to be more accurate about GNU tar:

    Some backup tools that you might wish to use emit warnings or errors
    if the files they are trying to copy change while the copy proceeds.
    This situation is normal, and not an error, when taking a base backup
    of an active database; so you need to ensure that you can distinguish
    complaints of this sort from real errors.  For example, some versions
    of <application>rsync</> return a separate exit code for
    <quote>vanished source files</>, and you can write a driver script to
    accept this exit code as a non-error case.  Also, some versions of
    GNU <application>tar</> consider it an error if a file is changed
    while <application>tar</> is copying it.  Fortunately, GNU
    <application>tar</> versions 1.16 and later exit with <literal>1</>
    if files changed during the backup, and <literal>2</> for other errors.

so your version of 'tar' might be fine.

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>          http://momjian.us
  EnterpriseDB                               http://www.enterprisedb.com

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

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