Apple has a reputation for making products that “just work,” but many Mac users may still need to occasionally troubleshoot their desktop or laptop. Thankfully, there are a number startup options that are available on recent Macs to aid in both troubleshooting and system management. Here’s a look at seven essential Mac startup options that every OS X user should know.

Recovery Mode

Starting with the release of OS X Lion in 2011, Macs have offered a Recovery Mode that users can access to diagnose hardware issues, restore Time Machine backups, manage hard drives, and even reinstall OS X itself. To use Recovery Mode, reboot or start your Mac and hold the Command and R keys simultaneously on your keyboard as soon as you hear the familiar startup chime. Keep holding as your Mac boots, which may take a few moments depending on its specific configuration. You can let go of the keys when you see a screen similar to the screenshot below.

Recovery Mode is possible thanks to the installation of a hidden recovery partition on your Mac’s hard drive, and allows the user to perform the aforementioned tasks without needing an OS X DVD or USB installer. To perform recovery tasks on older versions of OS X, such as OS X 10.6 Snow Leopard, users needed to boot from the install DVD.

A recovery partition will be created by default on new OS X installations and upgrades, but not every Mac configuration is supported, including RAID system drives. Further, if your Mac’s drive lacks a recovery partition for any reason, you may still be able to access OS X recovery tools via OS X Internet Recovery, which loads the recovery information directly from Apple’s servers. To use this feature, you’ll need an active Internet connection and a Mac introduced after the public availability of OS X Lion, which includes the Mid-2011 MacBook Air and up.

Startup Manager

Most Mac users will probably only ever use the single drive that came with their system. But for those who want to use multiple internal drives or partitions, Windows via Boot Camp, or boot to external drives, you’ll need to use the Mac’s built-in Startup Manager. Simply reboot your Mac and hold the Alt/Option key on your keyboard as soon as you hear the Mac’s startup chime. After a few moments, you’ll see all of the bootable devices appear on your screen accompanied by their corresponding icons and volume names.

The Mac Startup Manager will update as needed, so if you add or remove bootable drives or devices on your Mac, the list will automatically display the current options. You can use your mouse, trackpad, or keyboard to select the desired drive, and either click on its upward arrow button or press Return once you’ve made your selection. As long as the Mac is compatible with operating system contained on the selected drive, your Mac will continue booting the designated operating system.

Examples of when you may need to use the Mac Startup Manager include booting to your Windows Boot Camp partition, booting to a complete cloned backup of your system drive, or reinstalling OS X from a DVD or USB drive.

The Mac Startup Manager works great if you have a number of boot options from which to choose, but your Mac also recognizes a few additional startup keys that direct it to boot immediately from a specific source. These keys include holding the C key during boot to boot directly from an inserted CD, DVD, or bootable USB drive, and holding the N key to perform a NetBoot to a compatible network server.

Safe Boot

If you’ve ever worked in the Windows world, you may be familiar with Windows Safe Mode, which starts the operating system with the bare minimum level of drivers and software to help you isolate the cause of a software issue or conflict. OS X offers a similar mode called Safe Boot. Just as with its Windows counterpart, OS X Safe Boot should be used to help troubleshoot issues that may be caused by corrupt or incompatible software, or to help isolate software issues from hardware failures. To use it, press and hold the Shift key on your keyboard as soon as you hear your Mac’s startup chime. Keep holding Shift until you see a gray progress bar appear beneath the Apple boot logo.

When triggered, Safe Boot will force a check of your startup volume’s integrity, load only the minimum required OS X kernel extensions, disable all user fonts, clear font caches, and disable all startup and login items. All of these tasks equate to a significantly longer boot time compared to the default “normal” OS X boot process, so don’t panic if your Mac takes longer than usual to boot.

Once you reach the usual OS X login screen or desktop, you’ll notice the words “Safe Boot” in red letters in the menu bar. You’ll also likely notice slower overall system and graphics performance, as OS X is using default drivers to help you track down your software or driver issue. You won’t want to use Safe Boot day-to-day, of course, as many common and useful functions are not available in this mode, but it is an essential step in troubleshooting your Mac. When you’re ready to return to “normal” mode, just reboot your Mac without holding down the Shift key.

Reset PRAM

Your Mac’s parameter random-access memory (PRAM) stores important information such as the type and identity of your OS X system drive, the presence of any other internal drives, the number and type of connected devices, screen resolution, and speaker volume. If your Mac isn’t acting as expected, a PRAM reset is usually the first and easiest troubleshooting step to try. You’ll also want to make sure you preform a PRAM reset after you replace your Mac’s hard drive, unless you like waiting five minutes for the system to boot while it searches in vain for the old missing disk.

To reset PRAM, shut down your Mac and find the Command, Option, P, and R keys on your keyboard. You’re going to need to power your Mac up, and then press and hold all four keys simultaneously as soon as you hear the startup chime. It’s a little tricky at first, and you may miss it on the first attempt, but just keep rebooting your Mac until you’re comfortable contorting your fingers to reach all four keys at the same time.

Keep holding the keys until your Mac reboots itself and you hear the startup chime a second time. At this point you can release the keys and your Mac should boot as normal. Note that settings such as resolution and system speaker volume will be set to defaults, so don’t be startled if your Mac’s startup chime is a bit louder on the second boot.

Verbose Mode

There’s a whole lot going on when your Mac boots, but Apple, always concerned about design and user experience, hides the details behind the familiar light gray boot screen. This makes booting your Mac a simple and pleasant experience, but can also hamper troubleshooting efforts.

To see what’s really happening during your Mac’s boot process, you’ll want to enable Verbose Mode, which lets you see the messy details during boot in order to identify any drivers, kernel extensions, or other issues that are causing your Mac grief. To use Verbose Mode, reboot your Mac and press and hold the Command and V keys simultaneously as soon as you hear the Mac startup chime. You’ll soon see quickly moving rows of text instead of the gray boot screen, and you or a tech support rep will be able to see exactly what is causing the issue you’re attempting to troubleshoot.

Single User Mode

Related to Verbose Mode, Single User Mode also shows you the full details of your Mac’s boot process. But instead of finishing the boot and bringing you to the default OS X login GUI, it gives you a text terminal which can be used for everything from advanced troubleshooting to hard drive repair.

To boot into Single User Mode, reboot your Mac and hold down the Command and S keys simultaneously until you see white text appear on the screen. You can begin using the terminal once the boot process finishes and you see root# on the screen.

Your Mac’s Single User Mode is similar to that found in Linux, and many of the commands are the same between the platforms. Once you’re ready to exit Single User Mode, just use the command “exit” to restart the system and boot normally.

Enable Target Disk Mode

Target Disk Mode is a very useful feature exclusive to Macs that, in effect, lets you turn your Mac into an unnecessarily complex external drive. While in Target Disk Mode, you can connect your Mac to another Mac via FireWire or Thunderbolt and see the contents of the Mac’s drive mounted on the second Mac as if the drive were an external FireWire or Thunderbolt device. This not only lets you easily access data on a Mac’s hard drive, it also lets you use one Mac’s hardware to boot another Mac’s operating system and data.

To use Target Disk Mode, reboot your Mac and hold down the T key as soon as you hear the startup chime. Keep holding until you see a white FireWire or Thunderbolt logo appear on the screen (depending on your Mac’s hardware capabilities). You can now directly connect your Mac to another Mac with a FireWire or Thunderbolt cable and access the first Mac’s drive. When you’re done, unmount the first Mac’s drive from the second Mac in OS X and press and hold the first Mac’s power button until the system powers off.

Summary

It’s important to read over the description of each Mac startup option to ensure that you understand its use and purpose. Once you’re familiar with these options, however, just use the table below as a handy guide in case you forget the specific keys necessary for each option.

Startup Keys	Description
Command-R	Boot to OS X Recovery Mode
Alt/Option	Access Mac Startup Manager
C	Boot to CD, DVD, or USB
N	NetBoot
Shift	Safe Boot
Command-V	Verbose Mode
Command-S	Single User Mode
Command-Option-P-R	Reset PRAM
T	Enable Target Disk Mode

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