Macintosh Diagnostics Home

This is the default landing page used in our diagnostics NetBoot image. It will cover basic diagnostics tips as well as the use of all the tools provided within the image.

Diagnostics Image Overview

The diagnostics image is an image provided on both vlan 51 and 420 that can be accessed via NetBoot. It can be used to:

  • Test a hard drive for SMART, filesystem errors, file permissions and bad sectors
  • Diagnose hardware (RAM, sensors/fans, GPU/VRAM)
  • Recover deleted/corrupted files
  • Clone hard drives (for upgrading or backups)
  • Reset firmware passwords
  • Change the default startup disk (i.e to select other NetBoot sets)

The image is currently built upon Mac OS 10.10.2, to see if your Mac can run the latest version, see MacOSVersions. The provided applications are:

  • Techtool Pro 8
  • DiskWarrior
  • Carbon Copy Cloner
  • Disk Utility
  • Firmware Password Utility
  • Network Utility
  • Startup Disk

Diagnosing Startup Issues

Flashing question mark / Hanging during startup (spinning circle)

A flashing question mark indicates that for some reason, the machine is unable to find a suitable volume to boot from. This could indicate:

  • A missing (or failed/failing) hard drive
  • A missing (or corrupted) operating system

Use Disk Utility to see if the hard drive's S.M.A.R.T status to determine if the drive is failing. Otherwise check and repair the disk and file permissions. If problem persists, run a surface scan in TechTool to check for possible bad sectors on the hard drive.

If bad sectors exist, the hard drive of the machine needs replacing, otherwise attempt to re-install the operating system.

Can't NetBoot using 'N' key

If the Mac is firmware locked, booting using the 'N' key will be disabled (as well as booting from a CD using the 'C' key).

NetBoot sets not appearing under ALT boot menu

If the Mac is older, NetBoot may not appear as an option under the ALT boot menu. The only workaround to this is to either boot off of the local hard drive or install disc and open System Preferences to change the Startup Disk to your preferred NetBoot set.

Machine is firmware locked

If the Mac is firmware locked, the most basic way to remove the firmware password is to boot into the diagnostic image and run Firmware Password Utility under the Utilities menu.

If the password is forgotten or you are unable to boot into any volume to remove the password, you can forcefully remove the firmware password by following these steps:

  1. Turn off the Mac, remove battery (if laptop and possible) or unplug power
  2. Change the installed RAM amount (by either removing or adding a RAM module)
  3. Plug the Mac back in, turn it on
  4. Reset the PRAM by immediately holding COMMAND->OPTION->P->R until you hear the Mac's startup chime 3 times
  5. The firmware password has now been removed, you can now turn the machine off and revert your RAM to its previous state

Machine emits a series of beeps during startup (and doesn't start)

If the machine emits a series of beeps, match it to the following list to see what issue your machine is having:

  • 1 tone (repeats every 5 seconds) -> No RAM is installed
  • 3 tones (repeating every 5 seconds) -> RAM did not pass a data integrity check (could represent incompatible or bad RAM)
  • 1 long tone (booting while holding down the power button) -> Machine was manufactured before 2012 and has just started an EFI ROM update
  • 3 long, 3 short, 3 long tones -> EFI ROM is corrupted and machine is now in recovery mode
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Topic revision: r8 - 2016-05-11 - DevonMerner
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