dd command to copy a cd to a hard disk - Input/output error

Tomasz Ciolek tmc at goldweb.com.au
Mon Apr 1 15:25:24 EST 2002

 Hi All

 Please bear in mind that the blokc size of the cd is somethink like
 2300 bytes or so native, the blocksize of the iso9660 file system (on
 the cd is less then that and is about 2048. The difference is in the
 metadata about the 2048b od data that is encoded on the cd and used by
 ATAPI/ISO9660 drivers to make decisions as to where things are and how
 to get them, more importantly what things are.

 A read form a disk is diffent in many ways form the read form a cd but
 the atapi layer abstracts that so they look the same. 

 FS discrepancies can come into play...

 To correctly verify the cd image, if you must use dd, mount in on
 lookback as iso9660 and then dd+chensum it but make sure to use the
 count argument, to stop it at end of data.... 

 checksuming end of file will be different simce dd know shere the eof
 is and it will not try to read extrad stuff. If you are as much a 1 bit
 out in sizes, md5 will bve different...

On Mon, Apr 01, 2002 at 03:11:13PM +1000, Martijn van Oosterhout wrote:
> On Mon, Apr 01, 2002 at 12:40:37PM +0800, Daniel wrote:
> > Thanks to Simon, Brett, Tomasz and others for replies.  Yes your script fix 
> > worked well thanks. Now I've got the info I wonder what it all means!
> > I wanted to find out the correct block size to put into the 'dd' command 
> > ... does anything stand out to you as block size?
> > Anyway thanks very much for your help,
> The only way I know of finding the exact size is by mounting the cdrom and
> using the df command. Since this comes out of the TOC, it's probably
> possible to use the cdrecord -dumptoc (IIRC) command to get the size also.
> -- 
> Martijn van Oosterhout <kleptog at svana.org>   http://svana.org/kleptog/
> > Ignorance continues to thrive when intelligent people choose to do
> > nothing.  Speaking out against censorship and ignorance is the imperative
> > of all intelligent people.

Tomasz M. Ciolek	*
			* 	Everything falls under the law of change;	
<tmc at dreamcraft.com.au>	*	  Like a dream, a phantom, a bubble, a shadow,
<tmc at goldweb.com.au>	*	  like dew of flash of lightning.
			*	  You should contemplate like this. 
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