Compare iso to burned CD\DVD? Fedora 10

[D. Hugh Redelmeier]

| From: "Frank Murphy (Frankly3D)" <frankly3d at gmail.com>

| The one thing I can't find is how to compare
| the downloaded iso to the Burned media.
| Google on compare iso to cd(dvd)
| just brings up proprietry efforts.
| 
| Can someone supply the cli for this?
| I think:
| diff /path to iso -o loop  /path to/dvd ?

The simple command would be cmp:
	cmp file.iso /dev/cdrom
Of course you need to adjust those paths according to your system.

One problem with this is that the raw cd read may not yield EOF at the
exact end of what was burned.  So you need to limit the cmp to the
correct length.

What is that length?
	isosize file.iso
will tell you the number of bytes.

Then you can tell cmp:
	cmp --bytes=`isosize file.iso` file.iso /dev/cdrom

There is still a problem with some drives combined with some kernels
generating spurious I/O errors because they read ahead beyond the
burned part of the medium.  I'll leave that issue alone this time.