Troubleshooting a Mac
Quick, harmless, sometimes can help solve a problem.
- Reset PRAM: on boot, hold down Apple + Option + P.
- Reset NVRAM: on boot, hold down Apple + Option + N + V.
- Boot in Verbose mode: on boot, hold down Apple + V. Watch for errors as Mac boots, and google any errors found.
- Drain power cache: with computer off, take out battery, unplug from charger, and hold down power button for 15 seconds. Can sometimes fix a Mac that won't boot.
- Delete a program's .plist settings file: Found either in ~/Library/Preferences or in /Library/Preferences. This clears all settings for a program.
- Run Console.app to check for recent errors in Mac's log files.
BACK UP FILES before going on to any advanced diagnostics or tricks.
Install Combo Pack updates
This can solve a variety of confusing problems.
Hardware troubleshooting with Apple Diagnostics
- On newer models, you can start diags by pressing F2 on booting. (Diags are preloaded onto computer.)
- On older models, insert the install disk and hold down the D key while booting. Diags are model-specific so you can't use the wrong CD.
- AppleCare-covered users can download and install TechTool Deluxe for free. A good diagnostic but to convince Apple of system failure, you'll need to use the more official Apple diagnostics.
For hard drive failure
- Boot into Single User Mode by holding down Apple + S on boot.
- When system has loaded, enter
fsck -fyto check disk.
Target Disk Mode
See Target Disk Mode for how to use. Boot a Mac using another Mac's hard drive so you can:
- Access the internal hard drive without depending on it to boot the system
- Run Disk Utility to repair disk permissions
- Run Disk Warrior for advanced repair techniques
Archive & Install
Reinstalls system without touching user files (in theory). A messed-up install might be fixed this way.