macbook pro encounters prohibited sign while booting with USB My macbookpro is completely empty and the only option that I have is just internet recovery. I downloaded el capitan and with help of the terminal in the internet recovery build a bootable OSX el capitan. So when I hit c in startup, apple logo appears. Meanwhile progress bar goes half way and suddenly apple logo changes to prohibited sign. I also made a mavericks bootable usb. same results.
In verbose mode, you will find that OSX gets stuck at:


  Still waiting for root device


This error usually happens when your media used to boot OSX is not detected properly and can't be mounted. You can therefore try these methods to get it to work:


Changing the port you insert your USB into
Remaking the bootable media
Getting a new USB


If all fails your device may need special drivers of some sort. You can also check it out with an Apple Genius.