Problems while reading from /dev/cd0

[Gerhard Schmidt]

Am 23.08.2016 um 13:12 schrieb Dimitry Andric:
> On 23 Aug 2016, at 08:50, Gerhard Schmidt <estartu at ze.tum.de> wrote:
>>
>> I'm having some very curios Problems while reading from an BD-R recorded
>> as a tar directly on the disk without a filesystem.
>>
>> When i try to read the Disk via 'tar tvvf /dev/cd0'
>>
>> i get the following output
>>
>> -rw-r--r--  0 root   wheel 5793264611  1 Jan  2015 file1.db
>> tar: Error reading '/dev/cd0'
>> Archive Format: POSIX ustar format,  Compression: none
>> tar: Error exit delayed from previous errors.
>>
>> reading the whole file via 'dd if=/dev/cd0 of=backup.tar bs=2048' and
>> than 'tar tvvf backup.tar' the file is read without a hitch. So the data
>> on the disk is OK but can't be read directly by tar.
>>
>> if i try the dd without the bs=2048 i get
>>
>> dd: /dev/cd0: Invalid argument
>> 0+0 records in
>> 0+0 records out
>> 0 bytes transferred in 0.000115 secs (0 bytes/sec)
>>
>> So there is a problem reading anything other than 2048 byte blocks from
>> a Disk.
> 
> Have you tried tar's -b option, to set the block size 2048?  Maybe that
> will help.

It does partially. extracting the files work but testing the archive
with tar t fails.

Estartu


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Gerhard Schmidt                | E-Mail: schmidt at ze.tum.de
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