I erased my Macintosh HD from Disk Utility with a journaled encrypted format and I wanted to install OS X 10.7 Lion. I left it to download and install overnight because it took about 16 hours.

When I checked it again it gave me a weird screen that has a circle with a slash inside it, like a stop sign. What can I do?

2 Answers 2


Is it this prohibitory sign?


Circle with Slash - could not load boot.efi, or some other issue

Does the Mac shut down after it shows the sign? http://support.apple.com/kb/TS3742:

If there are five new kernel panics within three minutes, the Mac will display a prohibitory sign for 30 seconds, and then shut down.

You could try repairing the disk or the OS X partition:

  • Hold command-R on startup
  • Open Disk Utility
  • Select the disk (like APPLE HDD HTS541010A9E662 Media) and press the Repair Disk button
  • Select the OS X partition (like Macintosh HD) and press the Repair Disk button

You could also try erasing and reinstalling again, but choose Mac OS Extended (Journaled) instead of Mac OS Extended (Journaled, Encrypted). You can enable FileVault later from System Preferences.

If the drive is grayed out in Disk Utility or not shown when you try to reinstall OS X, you might need to replace it with another drive.

  • when i startup , the only drive available is the mac base system , i opened osx internet recovery and checked my apple HDD and macintosh HD and reformatted macintosh HD to extended journaled , and still they're not appearing at startup when i press the option button , do i have to install lion now?
    – user53781
    Commented Jul 25, 2013 at 6:35
  • both disks appear to be fine without any problems, and my mac didn't shut down after the sign , it was just opened
    – user53781
    Commented Jul 25, 2013 at 6:35

Hold cmd + R together whilst booting and it will bring you into internet recovery. Type in your Username and the password. After that a gray screen will come up. Go to Disk Utility and erase Macintosh HD, then go back and click on reinstall Mac OS X which will get a new copy of the OS.

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