Checksum a DVD

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How to checksum a DVD, for example an installer DVD of an operating system.

Sometimes you get a DVD that you would like to checksum. For example one to install a new operating system.

A constant question is whether the content on this DVD is legitimate or not. Luckily, checksumming a DVD or CDROM is not so hard.

Get size of DVD image:

> ftp ftp.freebsd.org
> cd pub/FreeBSD/ISO-IMAGES-amd64/10.0
> ls

We observe that the size of the DVD image is:

2484742144

Copy entire DVD content to harddisk:

> dd if=/dev/cd0 bs=2k count=`dc -e "2484742144 2048 / p"` of=/tmp/dvdcopy

Checksum the create file and compare with pubilshed hashes:

> sha256 /tmp/dvdcopy

Byte-by-byte comparison:

> cmp /dev/cd0 FreeBSD-9.1-RELEASE-amd64-dvd1.iso 
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