Re: howto verify burn?
On Mon, 10 Mar 2003 06:57, Bob Proulx wrote:
> Osamu Aoki wrote:
> > My post on this thread needs few errata:
> > 1. CD image size can be obtained by "mount" the CD and run "df".
> Interesting. Thanks for educating us about that.
> > 2. Only "readcd" run with nexact CD size can extract the correct image
> > 3. "dd" tends to copy most data correct but losews last few KB of data.
> I have been reading this thread with great interest because I had
> determined the following behavior.
> cdrecord image-in.iso
> dd if=/dev/cdrw of=image-out-cdrw.iso # works
> cmp image-in.iso image-out-cdrw.iso # passes
> dd if=/dev/cdrom of=image-out-cdrom.iso # reports errors on last few kb
> cmp image-in.iso image-outcdrom.iso # fails
Interesting. I am now able to copy correctly and verify the iso using
readcd and the no of blocks yielded by df as per:
I am actually unable to do any good using dd or cat with my compliment of
hardware which comprises a genuine scsi 8 speed burned and a 24 speed ide
burner. It does not matter which burner I use to burn or which to read.
As part of my efforts to resolve this I read the README.verify by Joerg
Schilling that comes with the cdrtools package. Toward the end of it he
suggested that some OS, notably Linux, have read ahead problems and that
these problems may be overcome by using the -pad option to cdrecord.
That option did not help me at all, but since you only have half the problem
that I do maybe using it will help you.
I have seen cat /dev/cd?? > some.iso used successfully on a Linux system in
the past, but I do not recall the breed. Nor did I know the origin of the
cds, they were Debian 3.0r0 but they may have been pressed not burnt. Nor do
I know if the iso would have made the same md5sum as the official image.
Meanwhile, I can now successfully verify my cdrs which solves the original
problem. That leaves the failure of dd and cat as an open issue for me at