Tuesday, December 4, 2007

Create an ISO from a DVD

If you need to create backups of DVDs there are a multitude of ways people recommend doing them on the web. The easiest I found can be accomplished in a single command and creates an ISO file that can be mounted later if necessary. Even tried it with an old, uncopyrighted DVD movie and it worked well.

user@machine ~> dd if=/dev/dvd0 of=~/dvdcopy.iso bs=2048

Some might ask: Why the bs=2048 parameter?

The reason is that often burnt cds/dvds have a number of null sectors
appended to the actual iso on the disc. If you simply use dd without a block
count the resulting iso will not be identical to the iso from which the dvd
was produced. The same remarks apply to the use of cat /dev/dvd > your.iso.
Not to say that the result won't work, it might. But if you do `md5sum
your.iso` the sum will not match that of the original iso if the there are
any blocks of padding copied up.

To remount:
user@machine ~> mkdir /media/dvdcopy
user@machine ~> mount -t iso9660 -o loop ~/dvdcopy.iso /media/dvdcopy

There are some posts on the web stating that if mounting a DVD that the type needs to be set to udp instead of iso9660 however the iso9660 value worked fine.

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