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Date: Wed, 17 Nov 2004 16:51:01 +0000
From: Andrew Sinclair <syncman@optusnet.com.au>
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To: Kris Kennaway <kris@obsecurity.org>, questions@freebsd.org
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Subject: Re: 5.3-RC2 tar breaks operation with "(null)"
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Kris Kennaway wrote:

>On Tue, Nov 16, 2004 at 07:53:15PM +0000, Andrew Sinclair wrote:
>  
>
>>Hi everybodi!
>>
>>   At work I use a Windows eXPensive machine...
>>   I burned this tar dump onto a CD-RW...
>>   I'm using the new tar from 5.3-RC2 to read from the mounted CD-RW... 
>>It seems to have a problem with null blocks...
>>
>>bash-2.05b$ tar -xvf /dvdrom/20041116.tgz
>>...
>>x Ocean Care Day/OCD website/Website/OCD Photos/Presentation.ppt: (null)
>>tar: (null)
>>bash-2.05b$
>>
>>   I remembered that tar uses four blocks of 0x00 to indicate the end 
>>of an archive on a sequential device...
>>
>>   I might be able to get around it with another tar but...
>>    
>>
>
>Try an updated version of bsdtar, either by updating to 5.3-STABLE or
>installing the bsdtar port.  Alternatively, use gtar.
>
>Kris
>  
>
<>I checked the changelog for that. There is a minor change to its 
handling of failed writes to the archive, which is quite the opposite of 
what I am trying to do. My disc is unsuprisingly screwed and the 
drive/filesystem returns zero filled blocks where it fails to read. I 
managed to work around it with dd and gtar:

    dd if=/dvdrom/20041116.tgz of=/home/shared/mec/20041116.tgz
    gtar --ignore-zero --ignore-failed-read -xvf 
/home/shared/mec/20041116.tgz

So a PPT and a PNG were garbled. No big deal. Since bsdtar is now the 
default Tape ARchiver, shouldn't it include the options of its 
predecessor? I would assert --ignore-zero on plain files and allow 
--ignore-failed-read at least.