If your original system volume does not appear, the issue lies with that storage device.As always, back up any important data from that volume before you make significant changes. If the original system volume appears, but your Mac still cannot find a valid system or booter, you may need to reinstall OS X on that volume.You can also attempt to define the startup disk when booted from another system volume like an external OS X Recovery disk, as covered in Lesson 4, “OS X Recovery.” If your Mac starts up from the system on the volume, open Startup Disk preferences to reset the volume as the startup disk. If the original system volume appears, select it to start up from it.Hold down the Option key during startup and use the Startup Manager to locate system volumes. The Mac computer’s main processor and components are probably working correctly, and you may only have a software issue. If your Mac passes the POST, but you are left with a flashing dark gray question mark folder icon, it means the firmware cannot locate a valid system volume or booter file. If this is the case, you’ll be best served by taking your Mac to an Apple Store or Apple Authorized Service Provider. Is the Mac plugged into an electrical outlet? Are the keyboard and mouse working properly? Ultimately, a failure to pass the POST is usually indicative of a serious hardware issue. You can always check for simple things first. If this is the case, your Mac has a fundamental hardware issue. You may also hear a series of diagnostic tones or see a series of power-on flashes. If you don’t hear the startup chime or see the power-on light flash, the Mac hardware did not pass the POST. The key to troubleshooting at this point is to determine whether this issue is related to the Mac computer’s hardware or system volume. Issues at the firmware stage are indicated by the inability of your Mac to reach the light gray screen with the dark gray Apple icon. The ramifications of each diagnostic startup mode are covered with each stage throughout this section.
These three modes are initiated at the firmware stage but affect the remaining system initialization process at each stage. Case in point, the troubleshooting sections outlined here are organized by each stage of the system initialization process.Īlso, throughout the remainder of this section, you will learn how each of the three primary OS X diagnostic startup modes-verbose mode, safe mode, and single-user mode-help resolve or identify issues. Once you can identify the various stages-and know which processes and files are responsible for each, you are well on your way to diagnosing any startup issue.
Apple Pro Training Series: OS X Support Essentials 10.9: Supporting and Troubleshooting OS X Mavericks
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