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What does it mean when I get the following prompt in recovery mode:

(4, 9204)

The drive is corrupted and needs repair. Use Disk Utility to repair the drive.

I have tried. No disks even show up on disk utility. It just keeps spinning and thinking when I try that. Can't even click on anything.

Then you will need to reformat and reinstall OS X. Backup your files if you can.

Install Sierra or El Capitan from Scratch

Backup if possible before continuing.

Restart the computer. Immediately after the chime hold down the Command and R keys until the Apple logo appears. When the Utility Menu appears:
Select Disk Utility from the Utility Menu and click on Continue button.
When Disk Utility loads select the volume (indented entry, usually Macintosh HD) from the Device list.
Click on the Erase icon in Disk Utility's main window. A panel will drop down.
Set the Format type to Mac OS Extended (Journaled.)
Click on the Apply button, then wait for the Done button to activate and click on it.
Quit Disk Utility and return to the Utility Menu.
Select Install OS X and click on the Continue button.

最后更新：2017-10-03 09:11:30