Re: [CentOS] sha256sum a dvd

On Mon, Apr 24, 2017 at 12:53:36PM -0400, James B. Byrne wrote:

CentOS-6.9

I am trying to verify a locally created dvd. I am using sha256sum in this fashion: sha256sum /dev/sr0

Which gave this result:

sha256sum: /dev/sr0: Input/output error

So I tried this: sha256sum /dev/cdrom

Which, after some time, also produces:

sha256sum: /dev/cdrom: Input/output error

What does this mean and how do I fix it?

It means that you're getting an error while reading one of the sectors of the DVD. It might be a problem with the disc, but it could also be a problem with the hardware.

Try doing a dd to copy all the bits to a local file, and pay attention to see if it has a problem reading the disc. Then run a sha256sum on the file it created.