8. System Management: Lesson Twenty-seven

Question 1

What are the primary system initialization stages in OS X?

What are the visual and audible cues of these items?

Answer 1

Each primary stage of system initialization can be indicated by the following:
• Firmware: startup chime or bright flash of the power-on light, followed by a light-gray screen on the primary display;
• Booter: a dark-gray Apple logo on the primary display;
• Kernel: a small dark-gray spinning gear or spinning Earth icon below the Apple logo; and
• System launchd: a white screen on all displays followed by the login screen

Question 2

What does the firmware do?

What’s the Power-On Self-Test (POST)?

Answer 2

The firmware initializes the Mac computer’s hardware and locates the booter file on a system volume.
The POST checks for basic hardware functionality when a Mac powers on.

Question 3

What role does the system launchd process serve during system startup?

Answer 3

The system launchd process is ultimately responsible for starting every system process.
It also manages system initialization and starts the loginwindow process.

Question 4

Which items are automatically started by the system launchd during the system initialization process?

Answer 4

During system initialization, the system launchd process automatically starts:
• /System/Library/LaunchDaemons
• /Library/LaunchDaemons
• /Library/StartupItems (via SystemStarter), and
•/etc/rc.local UNIX script (if it exists)

Question 5

What are the primary user session stages in OS X? What are the visual and audible cues of these items?

Answer 5

Each primary stage of the user session can be indicated by the following:
• The loginwindow process displays the login screen
• The user launchd process loads apps like the Finder after user authentication, and
• The user environment is active any time the user is logged in to the system

Question 6

What’s the difference between launch daemons, startup items, launch agents, and login items?

Answer 6

Launch daemons and startup items open during system initialization by the system launchd process on behalf of the root user.
Launch agents and login items open during the initialization of the user environment by the user’s specific launchd process.

Question 7

What are Safe Sleep and Power Nap?

Answer 7

Safe Sleep is a feature of all OS X–compatible portable Mac computers that saves the system’s state to permanent storage in cases where the computer’s battery drains completely.
Power Nap is a feature on Mac computers introduced after mid-2011 that use all-flash storage. Power Nap allows a Mac to automatically wake in a low-power mode so the system can perform a variety of app and system updates.

Question 8

What happens during user logout?

Answer 8

During user logout, the user’s loginwindow process does the following:
• Requests that user apps quit
• Automatically quits user background processes
• Runs logout scripts
• Records the logout to the main system.log file
• Resets device permissions and preferences to their defaults, and
• Quits a user’s loginwindow and launchd processes

Question 9

What happens during system shutdown?

Answer 9

At system shutdown, the loginwindow process logs users out and then tells the kernel to quit remaining system processes.
After the kernel quits system processes, the Mac shuts down.

Question 10

Which keyboard shortcut is used to start up in safe mode?

Answer 10

A startup in safe mode is initiated by holding down the Shift key during system startup.

Question 11

Which keyboard shortcut can be used to temporarily choose another startup disk?

Answer 11

Holding down the Option key at startup opens Startup Manager, which enables you to temporarily choose another startup disk.

Question 12

Which changes are made when OS X starts up in safe mode?

Answer 12

A startup in safe mode performs the following permanent actions:
• Attempting to repair the system volume structure
• Deleting system KEXT caches, and
• Deleting font caches

Question 13

Which items aren’t loaded when OS X starts up in safe mode?

Answer 13

When performing a startup in safe mode, OS X doesn’t load:
• Third-party kernel extensions (KEXTs)
• Third-party launch agents
• Third-party launch daemons
• Third-party startup items
• Third-party fonts
• Any user login items, or
• Any user-specific launch agents

Question 14

How do you further resolve an issue that disappears when a Mac successfully starts up in safe mode?

Answer 14

If an issue disappears when a startup in safe mode is successful, you must find and remove the third-party startup resource that caused the issue.
The best way to isolate the problem is to start up the Mac in Verbose mode and then observe where the startup process fails.
Verbose mode is initiated by holding down Command-V during system startup.