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. -- Jonathan Billings <billings at negate.org>