Once you’re in macOS Recovery, launch Disk Utility and proceed to run First Aid as discussed above. Press and hold the power button until you see a prompt that says “Loading startup options.” A set of one or more drives should appear along with a gear icon labeled Options. If First Aid finds any errors, it’ll attempt to automatically fix them. Macintosh HD (assuming you haven’t renamed the startup volume) Launch Disk Utility and click First Aid followed by Run, selecting volumes in the following order: When your Mac starts up, it performs a quick consistency check to scan the startup disk and to verify the partition scheme (the space where volumes exist) and volume directory structure (which catalogs the stored files and folders). But first, doesn't it make sense to ask what First Aid actually does? If you suspect problems with your startup drive due to performance issues or erratic behavior, running First Aid certainly won’t hurt. If your machine is running fine, this troubleshooting guide is not for you. You might see a black screen, you could get an error message, or your computer may hang on the white Apple logo. These tips are for instances where your Mac refuses to boot. We’ll show you how to use features like Disk Utility's First Aid, fsck, and tools built into macOS recovery to revive a Mac that refuses to start. Save yourself time and money by trying to fix it yourself. You don’t need to take your machine to a service center for repair yet. macOS includes some simple fixes that can help get everything right straight away. There’s no need to panic if your Mac won’t start.

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