Hey guys, I am currently on a MacBook Pro (2015, Retina). About six months old. I am unable to start my mac today and it repeatedly showed me the prohibited sign preventing me from doing a normal startup which I was able to do the night before. My concern is that I might lose my files on the HDD and will my HDD data be affected? Thanks in advance.
Dean
MacBook Pro (Retina, 13-inch,Early 2015), iOS 9.1
Hi Dean,
I know how nerve-racking it can be to have your Mac boot up to a big "NO" sign. Fortunately this doesn't necessarily mean that you've lost any data, but that your Mac can't locate a valid System folder to start up from. Typically this arises as a result of damage to the operating system as opposed to data, and can usually be resolved by reinstalling Mac OS X via OS X Recovery (or Internet Recovery as necessary).
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.
About the screens you see when your Mac starts up
https://support.apple.com/en-us/HT204156
All my best.
Prohibited sign on boot preventing startup
