A law is a law, irrespective of how many people ignore it. It may not be just, it may not be enforced, it may not be thought well of, but it is a law. That, however, is neither here nor there.
The "fair use" clause of copyright law states that you're allowed to make a backup for personal use - and while this is debated a lot, no one is gonna sue you for making a backup copy of a DVD you own if you don't share it.
That said, KnifeMissile was right on the money,
Doom9 is all you'll ever need to know.