Udi u Restore (CMD + R) i pokusaj Repair Disk s Disk Utility-jem ili vratiti backup iz Time Machine-a (ako postoji). Zadnja opcija ti je reinstalirati OS X.
Prohibitory symbol
When you see a circle with a slash symbol instead of the Apple logo, it means your Mac couldn't find a valid System Folder to start up from.
If you're using your Mac at a school or business, it might be trying to start from the wrong version of OS X. Contact your IT department for more help.
If this is your personal Mac, try reinstalling OS X by using
OS X Recovery.