quick (and perhaps foolish) question: MD4sum of CD

[Michael Schwendt]

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On Fri, 26 Sep 2003 11:56:56 +0300, Mikko Paananen wrote:

> On 2003-09-26 at 07:36, Tom Diehl wrote:
> 
> > "md5sum /dev/cdrom" The problem with that is that it is possible for it
> > to fail and the cd still be good or so I am told.
> 
> That won't usually work, md5sum will try to read past end of the disc,
> generate an error and give you wrong checksum.

No. It won't, because Tom mentioned DAO mode (Disk-At-Once) where you
don't get any run-out sectors at the end of the CD. I think in
cdrecord 2.0, it's called SAO mode (Session-At-Once).

> You have to read exactly right amount of data, isosize will give the
> size of iso9660 filesystem on disc:
> 
> dd count=$[`isosize /dev/cdrom`/2048] bs=2048 if=/dev/cdrom | md5sum -
> 
> (2048 is the block size on cdrom.)

There's also the "readcd" utility to read an ISO image.


- -- 
Michael, who doesn't reply to top posts and complete quotes anymore.

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