av Morse » tir 21.10.2014 16:34
Mac models introduced since OS X Lion debuted in 2011 have the ability to restore themselves as long as they're connected to the Internet. Some Mac models that shipped before Lion will work with OS X Internet Recovery too (with a firmware patch) — Apple has a list on their support site.
To access OS X Internet Recovery, hold down the command, option, and R keys simultaneously on boot.