The best thing to do is let the process run it’s course, as it may take a while and you don’t want to interrupt either the initial scanning for drive problems, or the repair attempts assuming any issues have been discovered on the drive. The repair process can take a while if there are a lot of errors on the drive, but oftentimes there are no problems found and so there will be nothing performed.

Repair Disk is now possible, click on “Repair Disk” to repair the boot volume.

Select the boot volume or partition from the left menu and click on the “Repair” tab.At the Mac OS X Utilities screen, select “Disk Utility”.Reboot the Mac and hold down Command+R to boot into Recovery, or hold down OPTION.How to Repair a Mac Boot Disk with Disk Utility in Mac OS X We’ll cover exactly how to do this, step by step. Once booted into Recovery mode you’ll find the limitations on Disk Utility’s repair function has been removed, and you can go about repairing the boot disk as intended. The trick is to boot the Mac into Recovery Mode first, and run the Repair function from there. While this is still the case while booted in most versions of Mac OS X, you can repair the Mac OS X boot disk thanks to Mac OS Recovery Partition, preventing the need from using an external boot drive to repair the disk.

How to boot to os x utilities