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.
Content from Blinking Question Mark should eventually go here.
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.