Mac Startup and Software problems - Troubleshoot
Mac Startup and Software problems
Mac OS X is resilient. It has a UNIX core which is mature, tested, and — more importantly — stable. It's a modern OS that's as flexible as it is powerful, limited only by the end users operating the system.
Clues to the causes of Mac startup problems can be found by analysing when in the boot process the system fails. Problems may be related to the power supply, battery, hard drive, logic board, OS corruption or an issue with a user account.
Isolating where the problem is occurring is the focus to finding the solution. Unplugging any external peripherals (disk drives, printer, etc.) is the first step to help narrow down the problem.
Step through the following points:
Does the system turn on?
If your Mac won’t power on at all (no Apple chime), likely suspects are a failed power supply, a bad logic board, a faulty battery or a bad AC adapter (on portables).
Macs also have another battery, called the PRAM (or NV-RAM) battery, that saves things like network settings, choice of startup drive, etc. If the date and time reset each time you unplug the Mac you need a new PRAM battery. A dead or dying PRAM battery can prevent a Mac from booting or cause erratic behavior. Sometimes plugging in the computer and letting it sit for 30-60 minutes recharges the battery enough to permit booting.
Clearing the PRAM
Power off your computer. Then power the device on while simultaneously holding down the [command]+[option]+[P]+[R] keys. You should hear the Apple chime before the computer reboots. Continue holding the keys down until you hear the second Apple chime to clear the PRAM.
Disable extensions on boot
Power on or restart the computer while holding down the [shift] key. Continue to hold down the key to disable extensions and login items from loading during the boot process. From a desktop with extensions disabled, "safe mode" will allow the end user to remove the offending app and boot normally.
Use the Boot menu
Power on or reboot the computer while holding down the [option] key. The boot process will halt and bring up the menu selection that lists all the bootable devices connected to that computer. Highlighting the desired device and pressing the [enter] key will redirect the boot process to that device.
Try using the Recovery partition
Power on the computer while holding down the [command]+[R] keys. This command directs the boot process to target the recovery partition available on computers running OS X 10.7 and newer.
In the event that the Recovery partition was not created or is not available, newer Apple computers may be able to use OS X Internet Recovery to boot their Macs from Apple's servers over the internet to perform the same tasks available as if booting from a local partition.
Use Verbose mode
Power on or reboot the computer while holding down the letter [V]. Verbose mode will load a terminal-like screen that logs the boot process in real-time to identify the source of any particular errors that may be preventing the computer from booting properly.
Use Single user mode
Power on or reboot the computer while holding down the [command]+[S] keys to enter Single-User mode. This mode will boot the Apple computer into a terminal-only mode where bash commands may be entered to perform further troubleshooting from the command line.
Does the Mac make any noise?
Listening to your computer can provide helpful clues to startup problems. If your Mac doesn’t make any noise at all when switching it on, or if you hear the fans running but nothing else, you may have a faulty power supply or logic board.
Sometimes a Mac will power on but the hard drive will make ticking sounds. This often indicates a failed or failing hard drive.
Mac startup tones and blinking lights
The Mac’s distinctive startup chime is more than an sound, it indicates a successful hardware (POST) test. If you don’t hear the chime but instead hear a single tone, a series of tones, or see blinking lights, your Mac is indicating a hardware problem. This may be the logic board, bad RAM, the power manager, a video card, etc..
Once the screen turns grey the hardware tests are complete, and the Mac looks for a boot volume. The startup process now targets the GUI software (Desktop).
Flashing question mark with folder, or circle/slashThe flashing question mark or a circle/slash means your Mac can’t find a valid startup disk. This can indicate a corrupt installation of Mac OS X or a failed (or failing) hard drive.
You can try the Apple Disk Utility to repair the disk. If the drive is OK after repairs but the Mac still won’t boot, do an Archive & Install of Mac OS X to replace the corrupted operating system.
When the Apple Logo appears your Mac has found a valid system disk, and Mac OS X begins loading.
Apple logo with spinning gear
Once the spinning gear appears the BSD kernel (Darwin) has become operative and begins loading device drivers. Shortly thereafter it transfers command to the launched process.
When a Mac stalls at the Apple logo or the logo with a spinning gear, it is probably caused by a corrupt Mac OS X installation. There may also be trouble accessing an internal or external hardware component, but this is less than likely.
Rebooting your Mac in Safe Mode can sometimes get things working well-enough that a second, normal reboot then works normally Hold down the Shift key at startup to boot in Safe Mode. DiskWarrior is also a commercial program that me help. If that doesn’t work, an Archive & Install may be needed.
Mac blue screen or blank desktop
After the Operating System has finished loading the login window process manager takes over and places you at your User desktop. A hang at a blue screen, at the login window, or at the image of your blank desktop often indicates a Problem with a User Account. Corrupt Fonts or bad Preference Files (.plist) are other common culprits.
Setting up a second admin account on your Mac is helpful for troubleshooting account problems. Safe Boot may help too, as that bypasses non-essential fonts and user startup items which you can then remove from your User Library folder.
Kernel PanicA kernel panic is an Operating System crash. Mac crashes have various appearances – the Spinning Beach Ball being perhaps the most familiar – or a screen slowly darkening from top to bottom before a multilingual warning appears (image below):
A kernel panic can happen at virtually any point in the boot process and may indicate a corrupt OS, an incompatible kernel extension, or a hardware problem. Try a Safe Boot to disable non-Apple extensions. If that doesn’t work try disconnecting peripherals, removing RAM, PCI cards, etc..
Boot Mac from another drive to troubleshoot
If your Mac has an optical drive you can boot from an Apple software install CD or DVD – insert your disc, restart and hold down the C key. Once the installer begins you can run Disk Utility (from the Utilities menu) or perform an Archive & Install. Recent Intel Macs can also boot from a USB flash drive which contains a bootable disk image.You can also use a clone of your Mac hard drive to boot a faulty system. This not only allows you to check, fix or copy data off the primary boot drive but continue working immediately when you have disk problems.