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OS X Lion: Startup ProcessIntroduction
This course covers the startup process for OS X Lion. Each stage in the process will be reviewed in detail,
which will help you troubleshoot and resolve startup issues.
Courses Overview
Course Objectives
Explain the Mac OS X startup process and its different stages
Recognize when the startup process if abnormal
Identify startup issues and possible fixes
Demonstrate when and how a Safe Boot is used
Determine and resolve common startup issues
The Startup Process
The OS X Lion startup process begins when the power button is pressed and ends when the desktop appears.
The entire process is comprised of these three stages:
1. Hardware
First, the system powers up, tests and prepares the hardware, and finds the startup disk with the boot
loader (program that places the operating system into memory).
2. Startup
The operating system loads and starts everything else required by the login stage. Most startup issues
occur at this stage.
3. Login
The selected user logs in (either automatically or using the login window) and the operating system sets
up the user's environment.
Audience
Technicians who wish totroubleshoot and service
Mac computers
Prerequisites
OS X Lion: Basics, Installation
Time Required
60 minutes
You will need...
OS X Lion (10.7),Mac computer, Printer
and Internet connection
OS X Lion: Startup
Introduction
Course Overview
The Startup Process
Stage 1: Hardware
Stage 2: Startup
Stage 3: Login
What is a Safe Boot?
Symptoms & Fixes
Troubleshooting Practice
Learning Resources
Contact Us
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Troubleshooting Tip
When troubleshooting a startup issue, first, identify how far the startup process has
advanced. After you know where the system is in the startup process, you can most
effectively troubleshoot the issue.
Learning Resources
"About firmware updates for Intel-based Macs" (HT1557)
"Intel-based Mac: Startup sequence and error codes, symbols" (HT2674)
"Mac OS X: 'Broken folder' icon, prohibitory sign, or kernel panic when computer starts" (TS1892)
"Mac OS X: Gray screen appears during startup" (TS2570)
"Mac OS X: Starting up in Safe Mode" (HT1455)
"Mac OS X: What is Safe Boot, Safe Mode?" (HT1564)
"Power or Start Up Quick Assist" (HT1149)
"Startup key combinations for Intel-based Macs" (HT1533)
Stage 1: Hardware
During this stage, your Mac receives initial power and checks hardware. Permanent software embedded in a
piece of hardware (firmware) loads and instructs the Mac to then load the boot loader (program that places the
operating system into memory).
What happens during this stage?
1. Power On and POST
When you press the power button, your Mac provides power to the logic board and performs a quick
check of the hardware. This hardware check is called the power-on self test, or POST. This test resides in
read-only memory (ROM) of the computer. If the POST is successful, you hear the startup chime and the
memory test completes. If a fault is detected during the test, you will not hear a normal startup chime.
Instead, you may hear error beeps. When this occurs, the screen remains black.
2. Firmware Loads the Boot Loader
The computer's firmware takes over. After the firmware loads, the Mac displays a blank gray screen. First,
the firmware decides from which disk to start the Mac (hard disk, installation disc, or NetBoot server).
Note: If FileVault is enabled, the correct password must be entered in order to continue.
Next, the firmware looks for a specific file called "boot.efi". That file is found in the
/System/Library/CoreServices/ folder. After the boot loader loads, you see the gray Apple logo on the
screen:
The Apple logo indicates that the Hardware stage has ended, and the Startup stage has begun.
Error Beeps: What do they mean?
1 beep = No RAM installed
2 beeps = Incompatible RAM types
3 beeps = No good banks
4 beeps = No good boot images in the boot ROM (and/or bad sys config block)
5 beeps = Processor is not usable
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5 beeps = Processor is not usable
Stage 2: Startup
During this stage, the Mac finds and loads files on the startup disk, and starts everything the Login stage
needs.
What happens during this stage?
1. Boot Loader
The gray Apple logo signifies that the boot loader has finished loading from the startup disk.
begin to load the kernel and related files.
2. Kernel Loads Files
While the kernel loads the driver for the root device, checks the directory and starts services
memory and other launch agents) it displays a spinning gear under the Apple logo:
3. Graphical User Interface Starts
When you see a dark linen background, the OS X Lion graphical user interface (GUI) has started.
GUI process that runs is called loginwindow, followed by windowserver which is responsible for
everything on the screen.
4. Login Window Appears
Finally, you can log in. Based on your preferences, OS X Lion logs in automatically or you will need to
enter your name and password at the Login window:
Stage 3: Login
During the final stage, OS X Lion starts looking for user accounts and user-owned files, and starts running
programs for the user. These include the Finder, Dock, and any login items the user has chosen.
What happens during this stage?
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1. User Environment
The Finder opens, along with other necessary background processes like the Dock:
2. Login Items
OS X Lion then opens login items (as set in the Users & Groups System Preference):
What is a Safe Boot?
Safe Boot is a special way to start up when troubleshooting. After a Safe Boot, the Mac will enter into Safe
Mode which will assist in isolating and identifying problems.
To perform a Safe Boot, hold the Shift key as the Mac starts up. The Safe Boot startup screen appears:
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What does Safe Boot do?
It forces a directory check of the startup volume
It loads only required kernel extensions (some of the items in /System/Library/Extensions)
It disables all fonts other than those in /System/Library/Fonts
It disables all startup items and login items
Deletes the dynamic loader shared cache at (/var/db/dyld/). A cache with issues may cause a blue screen
on startup, particularly after a Software Update. Restarting normally recreates this cache.
These changes can help resolve software or directory issues that may exist on the startup volume.
Warnings
1. Safe Boot may take longer than normal. When you see the progress indicator (spinning
gear), the disk's directory is being checked and or repaired. This process may take
several minutes.
2. You cannot perform a Safe Boot if the computer owner or administrator has enabled
firmware password protection.
3. If FileVault is enabled, the correct password must be entered.
Learning Activity
Perform a Safe Boot and explore Safe Mode. Your goal is to learn how the Mac behaves
while in Safe Mode.
1. Power on or restart your Mac.
2. Hold down the Shift key as the Mac starts up.
3. Once the desktop appears, try using DVD player, iMovie, Safari and other applications.
The behavior of some devices (such as an AirPort card or USB peripherals) may also vary in
Safe Mode. For more information on Safe Mode, refer to the OS X Lion: Troubleshooting
Tools and Techniques course.
Symptoms and Fixes
Here are frequent problems reported by users during startup. Follow steps in the order indicated below to
resolve the issue.
Symptom #1: Hardware Stage - Power-on self test (POST) Fails
Symptom #2: Hardware Stage - Mac displays blank gray screen or question mark
Symptom #3: Startup Stage - Mac doesn't progress past spinning gear
Symptom #4: Startup Stage - Startup process stops at dark linen background
Symptom #5: Startup Stage - Login window doesn't appear
Symptom #6: Login Stage - User environment doesn't appear
Symptom #7: Login Stage - Before completely starting up, Mac stop responding
Troubleshooting Tip
If the Mac can startup from the recovery partition, this tells you that the computer does not
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If the Mac can startup from the recovery partition, this tells you that the computer does not
have a system-wide startup failure. The problem can then be isolated to either the actual
hard drive hardware or the software on it.
Symptom #1: Hardware Stage - Power-on self test (POST) Fails
Summary
If you hear no chime, hear a series of error beeps, or see a flashing LED on the computer after you press the
power button.
Resolution
Before proceeding, consult hardware-specific resources to match specific LED codes or error beeps to specific
symptoms.
1. Remove any third-party or other added hardware (including RAM), internal or external devices, and try
again.
2. Reset the computer's PMU, SMU, or SMC to resolve power issues.
3. Reset PRAM and NVRAM:
a. Shut down the computer.
b. Locate the following keys on the keyboard: Command, Option, P, and R.
c. Turn on the computer.
d. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray
screen appears.
e. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
f. Release the keys.
4. Run Apple Hardware Test, if possible, to identify common hardware failures.
5. Perform any other appropriate hardware troubleshooting or repairs.
Back to top
Symptom #2: Hardware Stage - Mac displays blank gray screen or question mark
Summary
Upon startup, Mac fails to progress past blank gray screen or displays a folder with a question mark.
Resolution
This condition tell us that the firmware has not found the boot loader on a startup disk. If this screen displays
for more than a minute:
1. Reset PRAM and NVRAM:
a. Shut down the computer.
b. Locate the following keys on the keyboard: Command, Option, P, and R.
c. Turn on the computer.
d. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray
screen appears.
e. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
f. Release the keys.
If the issue persists:
2. Try starting from the recovery partition.
If you can start from the recovery partition, but resetting PRAM/NVRAM fails to resolve the blank gray
screen:
3. Reinstall OS X Lion.
Note: When a Mac displays a folder with a question mark (as seen below), it has searched all available
and is unable to find a startup disk that contains boot files.
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Back to top
Symptom #3: Startup Stage - Mac doesn't progress past spinning gear
Summary
Mac displays the gray screen with the Apple logo, shows a spinning gear, never progresses past it or shuts
down.
Resolution
This symptom signals that the kernel cannot completely load the operating system.
1. Continue to wait.
The system can perform a disk directory check automatically if it was shut down improperly. This process
may take longer on larger hard disks.
If you have decided that the startup has truly failed:
2. Start up the computer from the recovery partition.
Hold down "Command" and "R" keys at start up.
3. Run Disk Utility to repair the startup disk.
This can fix directory issues that can undermine the System Folder.
If the issue persists:
4. Reset NVRAM/PRAM to clear any boot settings that may cause this issue.
a. Shut down the computer.
b. Locate the following keys on the keyboard: Command, Option, P, and R.
c. Turn on the computer.
d. Press and hold the Command-Option-P-R keys. You must press this key combination before the gray
screen appears.
e. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
f. Release the keys.
Note: If the kernel could not progress and displays the prohibitory sign below, this indicates that the root
device or startup disk driver could not be found, disk verification failed, or the computer is not
with this version of the Mac OS.
Back to top
Symptom #4: Startup Stage - Startup process stops at dark linen background
Summary
The startup process stops at the dark linen background.
Resolution
When this occurs, OS X Lion failed to load its graphical environment and system services.
1. Start up into Safe Mode to see whether corrupt fonts or extensions are causing the issue.
Hold down the shift key during start up.
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2. Check the logs in Console (system.log or Console messages) for failure errors around the time of the last
boot attempt.
Console is a utility built in to OS X Lion that displays log files. You can check the Console if you can start
from the hard drive in Safe Mode, or check other log files using Terminal while started from the
installation disc.
If you cannot isolate the cause:
3. Boot from the recovery partition.
Hold down "Command" and "R" keys at start up.
4. Use Disk Utility to repair the startup volume's directory and/or permissions.
If Disk Utility reports no errors and you have repaired the volume's directory and/or permissions:
5. Reinstall OS X Lion.
Back to top
Symptom #5: Startup Stage - Login window doesn't appear
Summary
Mac is set to log in automatically, but does not.
Resolution
1. Go to System Preferences > Users & Groups.
2. Select Login Options.
3. Verify that Automatic login is turned on.
If you restart and the login window still doesn't appear:
4. Start up from recovery partition.
Hold down "Command" and "R" keys at start up.
5. Use Disk Utility to repair the startup volume's directory.
If this doesn't remedy the problem:
6. Reinstall OS X Lion.
Back to top
Symptom #6: Login Stage - User environment doesn't appear
Summary
After manual or automatic login, the Finder doesn't appear.
Resolution
The contents of the user's home directory may be the cause.
1. Log in as another user, if possible.
2. If the Dock or status menus aren't visible, try starting some applications.
If the issue is not isolated:
3. Start up from recovery partition.
Hold down "Command" and "R" keys at start up.
4. Run Disk Utility, and repair the startup disk.
If the problem is still not resolved:
5. Start from another volume.
6. Examine console logs on the problematic volume
(system.log and any crash logs)
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(system.log and any crash logs)
If the problem still exists:
7. Reinstall OS X Lion.
Back to top
Symptom #7: Login Stage - Before completely starting up, Mac stop responding
Summary
User can log in, but OS X Lion stops responding before the Mac has completely started up.
Resolution
Try suppressing login items.
1. Start up into Safe Mode to see whether login items are causing the issue.
Hold down the shift key during start up.
If you are able to login:
2. Go to System Preferences > User & Groups.
3. Click Login Items for the affected user.
4. Try deleting login items.
Restart and verify the fix. If this doesn't isolate the problem:
5. Reinstall OS X Lion.
Back to top
Troubleshooting Practice
Taken from the experiences of Apple service personnel, here is a troubleshooting scenario involving the
concepts presented in this course.
Scenario: Mac Doesn't Boot Up
A customer complains that his Mac doesn't boot up. It doesn't progress any further than a blank gray screen.
What procedures should you follow?
Click here to view answer
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