All Mac boot options explained
We all know that when you want to start up your Mac, you just press the power button and when you want to restart, you visit the Apple menu and choose Restart from there. But did you know there are several other Mac boot commands? These useful combinations help start up the Mac properly and fix system errors. We’ll explain more below.
Why are there different Mac boot options?
The simple answer is: to allow you to troubleshoot problems. If your Mac won’t start up in regular boot mode, or if it starts up but behaves erratically, you need to be able to diagnose the problem and fix it.
Different boot modes allow you to, for example, start your Mac with only the bare minimum of extensions loaded, so you can figure out if they are at the root of the problem. Or you can boot into Recovery Mode and run Disk Utilities to repair your disk, or, at worst, reinstall macOS.
What are the available Mac boot keys and options?
Here is a list of the different Mac startup keys and boot commands:
- macOS Recovery
- Startup Manager
- Reset NVRAM
- Safe Mode
- Apple Diagnostics
- Single-user Mode
- Target Disk Mode
How to access Mac boot modes and what they do:
macOS Recovery mode is used to install and reinstall macOS operating system.
- Hold down Command-R while starting your Mac to access the built-in recovery tools, including Disk Utility. This option allows you to reinstall the latest version of macOS that was installed on your Mac.
- To install the latest version of macOS that is compatible with your Mac, hold down Option-Command-R instead.
- If you want to reinstall the version of macOS that came with your Mac or the nearest one that’s still available, hold down Shift-Option-Command-R.
The Startup Manager allows you to choose which bootable volume to start up from if you have more than one connected to your Mac. You can also use this method to startup up from a Time Machine backup if it’s connected to your Mac.
- Hold down the Option (Alt) key while you start up your Mac.
- Choose the volume you want to boot from by clicking on it when the options appear on screen.
- Press Return.
If your Mac is having problems with sound volume, display resolution, or time zones, resetting the NVRAM can help.
- Shutdown your Mac then press the power button while holding Command-Option-P-R.
- Wait 20 seconds and release the keys or, if your Mac plays a startup chime, release the keys after the second chime. If your Mac has a T2 security chip, you can release the keys after the Apple logo appears and disappears on screen for the second time.
For more information, here is a video about SMC, PRAM & NVRAM reset.
Safe Mode is a diagnostics tool that allows you to determine whether problems you’re having on your Mac are being caused by software that loads when it starts up.
When you start up in Safe Mode, login items, system extensions not needed by the OS, and third-party fonts are not loaded. System caches are deleted, and the macOS runs a check of your startup disk.
- Start or restart your Mac while holding the Shift key.
- Release Shift when you see the login window.
- You may have to log in twice, and should see “Safe Boot” in the top right corner of the login window.
When you’ve ruled out all possible software errors and come to the conclusion that you have a hardware fault, Apple Diagnostics can help determine which piece of hardware is causing the problem.
- Disconnect all external devices except the mouse, keyboard, display, power cable, and Ethernet cable if you use one.
- Shut down your Mac.
- Turn on your Mac and then press and hold the D key. Keep holding it until you see a window on the screen, asking you to choose a language.
- Apple Diagnostics will now check your Mac for problems.
- When it’s finished, it will report what it has found and give you options for what to do next.
Single-user Mode allows you to troubleshoot the startup process on your Mac. However, it boots your Mac into a command-line interface, so you should only use it if you know how to work with the command line.
- Start up or restart your Mac.
- Press Command-S on Mac startup.
- The screen will turn black and display white text. You can now run UNIX commands.
Target Disk Mode
If you want to make your Mac appear as an external volume on another Mac, you can use Target Disk Mode. You can connect the Macs using one of the following cables:
- Thunderbolt 3
- Thunderbolt 2
- If your Mac has not been started up, press the power button and hold down the T key. When it’s finished booting, you’ll see a Thunderbolt, FireWire, or USB symbol on the screen.
- If it is already started up, go to System Preferences > Startup Disk and choose the boot disk, then click Target Disk Mode. When asked to confirm, press Restart.
Once the Mac has booted in Target Disk Mode, you can connect it to another Mac.
There are several different Mac boot options you can access by holding down different combinations of keys. Each has a different function, usually to help you fix problems with your Mac. Follow the instructions above to use the different modes. If you’re looking for a quick fix, download CleanMyMac X to help you resolve issues with your Mac.