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There is a small panic that goes through your mind when your Mac refuses to boot. It either means one of two things: you are spending the day getting your machine working or you are taking an expensive trip to the Apple Store.
Your Mac has a surprising number of startup options to help you get it working again. These can save you a lost afternoon of computer problems, and might even save you a trip to the Genius Bar.
How Startup Keys Work
The Mac’s startup sequence is so famous it is a trademark. The grey screen with the Apple logo is your sign that your Mac is starting up. Sadly, the latest Macs no longer make a sound without a few tweaks.
However, if you press a startup key combination before you see the Apple logo, you can change how your Mac starts. For most of these, you want to press your key combination before the grey screen appears when your Mac boots.
1. Booting in Recovery Mode: Command + R
Pressing Command + R starts your Mac in recovery mode. Recovery Mode is the catch-all of utilities you can use to get your Mac working. Disk Utility is here to help you verify and repair your system drive.
You can use Time Machine to roll your Mac back to an earlier point. There is also a utility to change the password on user accounts. Safari can help you search for solutions to any problems you have. If all else fails, you can download and reinstall macOS.
Nine times out of ten, you are going to be able to fix any problem with your Mac by using Recovery Mode. It takes up some space on your drive, but that is a small price for such a useful set of tools. However, there are other options to help you with more advanced issues.
2. Booting From an External Drive: Option
Pressing the Option key on boot displays a list of your Mac’s bootable drives. On a barebones Mac, you’ll see your system disk and the recovery partition (or if you are rolling old school, your optical drive). If you have set up a Boot Camp partition, you see this there as well.
If you forgot to change your startup disk to Windows, this would save you time, but that is not the main event. Instead, if you want to boot your Mac from a USB stick (or on older models, a DVD), this is the option you need. If you want to wipe a system for a clean install, you can boot from a USB macOS installer.
3. Apple Diagnostics/Apple Hardware Test: D
Holding the D key when booting up your Mac brings up the Apple Hardware Test or Apple Diagnostics. It depends on your Mac’s model year which you have. You need to disconnect everything connected to your Mac but a mouse and keyboard.
You can use this test to run either a quick or thorough check of your Mac’s hardware. The quick test takes around five minutes. The more extended test varies based on the amount of memory installed on your system.
If you are having weird issues with your Mac, this is the best place to start. This diagnostic issues can potentially help you skip a few steps when calling support as well.
4. Resetting the NVRAM: Option + Command + P + R
Hold Option + Command + P + R as your Mac reboots, and hold them until your Mac reboots a second time. NVRAM, or Nonvolatile RAM, is how your Mac saves specific preferences when it is powered off. NVRAM handles volume, resolution, time zone settings, and startup disk.
If you have problems with these preferences, use this option. Though to be honest, most troubleshooting guides start with clearing the NVRAM. Older Macs used PRAM for the same purpose, which is the source of the shortcut letters.
5. Resetting the SMC: Shift + Control + Option
If resetting the NVRAM does not fix it, your next step is resetting the SMC. The System Management Controller is reset by holding Shift + Control + Option. Resetting the SMC can help with many hardware issues. If your fans are running even when your Mac is idle is a good example.
It also addresses issues with sleep, the ambient light sensor, and keyboard backlight. It may fix some issues with your Mac’s battery charging.
6. Verbose Mode: Command + V
When something breaks during your Mac’s startup, hold down Command + V to switch to Verbose Mode. It allows you see the processes and steps hidden behind the gray Apple screen and progress bar. When troubleshooting your Mac’s slow or failing startup, use Verbose Mode.
If you have FileVault encryption enabled, you have to hold the keys until the login screen comes up. If you have a firmware password, you need to disable it.
7. Safe Mode: Shift
If you find that something is crashing your Mac during startup, you need to disable it. That is where Safe Mode comes in, accessed by holding Shift at boot. You can also use Terminal to restart in Safe Mode using the command:
sudo nvram boot-args="-x"
You cannot just restart your Mac to exit Safe Mode when you do it this way. You need to use the command:
sudo nvram boot-args=""
When you use this mode, your Mac disables almost everything but the basic system needs. It also forces a disk check, which may help fix some issues as well. Safe Mode does not fix most issues, but it does help you isolate a problem.
8. Single User Mode: Command + S
Single User Mode is going to be for people comfortable with the command line. Holding Command + S on boot drops you to a command line with root privileges. This prompt lets you run fsck and other Terminal commands. If you have a problem narrowed down and are comfortable with the command line, use Single User Mode.
FSCK can be a more verbose when working with your disks which might help you have a better idea of what’s wrong. It has the same restrictions as Verbose Mode for encryption and firmware passwords.
9. Target Disk Mode: T
If you want to copy data off of a Mac, Target Disk Mode is useful. Hold T when booting your Mac and then connect your Mac to another Mac using a Thunderbolt, Firewire, or USB-C. You can then use Migration Assistant or even Finder to copy the files that you need. This mode has a somewhat limited application, but it is one that can be helpful.
Mac Startup Keys for Every Situation
Many of these startup key combinations are for troubleshooting your Mac. It might not be a bad idea to play around with a few of these so that you are not taken by surprise when you have a problem. Recovery Mode has most of the tools that you need, but digging deeper never hurt anyone.
It never hurts to be familiar with the many steps Apple Support are going to ask you about. It cannot hurt when trying to get one of the limited Genius appointments at your local Apple Store.
Ever had a time that one of these startup options saved your Mac? Is there a Mac troubleshooting secret you think everyone should know? Let us know in the comments.
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