Valcon Systems. > Customer Support > Knowledgebase

Steps to take when your Mac won't start up


Step 1: Run Disk Utility

Recovery mode offers a number of useful troubleshooting options.

If your Mac won’t boot, there could be many issues at play. But the one I like to rule out right away—or repair, if possible—is any problem afflicting the hard drive. The easiest first step on that front is to run Disk Utility. On a Mac running Mountain Lion, you can run Disk Utility by booting into OS X Recovery Mode.

Make sure the Mac is off. (If it’s not responsive because it’s stuck on a gray, blue, or white screen, just hold down the Mac’s power button for several long seconds until it gives up and shuts off.) Hold down the Command and R keys, and power the Mac back up again.

Eventually, you’ll end up on a screen headlined OS X Utilities. (Once you see that screen, you can release the keys you were holding down.) Click on Disk Utility. Then, click on your Mac’s built-in hard drive in the left column of Disk Utility. (Usually, you’ll see two listings for your built-in drive: The first includes the drive’s size, like 500GB, in its name; and nested underneath it is your drive’s friendlier name. You want that second one.) On the lower right of the Disk Utility window, click Verify Disk, and then wait while Disk Utility does its thing.

Step 2: Safe Boot

Safe Boot limits what checks and functionality your Mac focuses on during startup, and performs certain diagnostics. It’s rare, but sometimes you can get your unhappy Mac to start up successfully with a Safe Boot, and then restart it normally, and everything returns to hunky-doryness.

Shut the Mac down, and start it up while holding down Shift. Safe Boot can take a while if it does indeed work. To get some feedback about what's happening, you might choose to start up while holding down Shift, Command, and V: That enters both Safe Boot and something called Verbose Mode, which spits out some messages about what Safe Boot is actually trying to do as it goes.

Be patient during your Safe Boot. If the Mac does start up, restart it from the Apple menu once the desktop finishes loading completely. If the Mac starts up normally, go on with your day. Otherwise, keep working through this list. In JV’s case, his Mac wouldn’t restart normally following a successful Safe Boot. So, we moved on to the harder-core options.

Step 3: Fsck for fsck’s sake

This step is actually kind of fun—at least when it’s not your Mac that’s under the weather. It’s fun because it feels so geeky.

Shut the Mac off, and start it up again while holding Command and S. You’re launching Single User Mode. You can release the keys when the intimidating black screen with messages in white text appears.

Wait until the command-line prompt appears, when all the text is done scrolling past. Then, you’ll type fsck -fy and hit Return. And wait. Possibly for several long minutes.

Eventually, after five different checks that take varying amounts of time, you should get to one of two messages: “The volume [your Mac’s name] appears to be OK” or “FILE SYSTEM WAS MODIFIED.” If you encounter the first message, type reboot and press Return. If you see the latter message, though, you’ll want to run fsck -fy all over again. You can retype the command and hit Return, or press the Up arrow once and then press Return.


Step 4: Reinstall OS

Remember OS X Recovery from Step 1? You can use it to reinstall Mountain Lion, too. Boot into Recovery mode, and then click to install Mountain Lion and follow the on-screen prompts.


Step 5: Reset the NVRAM, because, why not?

In the PowerPC days, we talked about resetting the PRAM. On modern Macs, the real term is resetting the NVRAM. The name refers to special memory sections on your Mac that store data that persists even when the Mac is shut off, like volume settings, screen resolution, and similar options.

Resetting that data isn’t harmful, and quite frankly it’s also rarely genuinely useful. But man, at this point, it can’t hurt.

You might need to grow an extra finger or two for this one, or have a friend help you out. Hold down all of these keys: Command, Option, P, and R, and turn on the Mac. Keeping holding the keys down until you hear the Mac restart again. Apple says to let it restart just the one time; I usually listen for a second reboot, and then release the keys.

In some cases, after performing this step, your Mac will restart normally. In other cases, if your luck is as bad as Julian’s was, you might instead see a progress bar on startup. If the progress bar fills up and then the Mac starts up, you’re likely good to go. In JV’s case, however, his Mac actually shut down at around the halfway point in the progress bar.

Was this article helpful? yes / no
Related articles How to Use OS X Boot Options to Troubleshoot Your Mac
The Apple Mac Boot Shortcuts
Reset Windows XP Activation
Undervolting in Linux via modified video BIOS
Create a Bootable Windows PE RAM Disk on a USB Flash Disk
Article details
Article ID: 15
Category: Apple IOS / MAC
Date added: 2013-10-11 16:13:12
Views: 193
Rating (Votes): Article rated 2.7/5.0 (7)

« Go back