Lesson 28—Troubleshoot Startup and System Issues

Question 1

How does a Mac with Apple silicon or an Intel-based Mac with the T2 chip ensure security during macOS Big Sur startup?

Answer 1

A Mac with Apple silicon or an Intel-based Mac with the T2 chip verifies every step of the startup process to ensure that the hardware and software haven’t been tampered with

Question 2

What are the 4 primary system initialization stages in macOS Big Sur? What visual and audible cues do these stages provide?

Answer 2

• Firmware—Power on. POST. Startup chime.
• Booter—The booter process starts. The Apple logo appears in the center of the main display.
• Kernel—Kernel startup. The progress bar appears.
• System launchd—Starting other items. The Apple logo is replaced with the login window.

Question 3

What does the firmware do? What’s the Power-On Self-Test (POST)?

Answer 3

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

Question 4

What role does launchd serve during Mac startup?

Answer 4

launchd starts macOS Big Sur processes, manages macOS Big Sur initialization, and starts the loginwindow process.

Question 5

What are two locations for launchd to find preference files that control how various processes are configured?

Answer 5

During macOS Big Sur startup, launchd uses preference files for LaunchDaemons in the following locations:
• /System/Library/LaunchDaemons
• /Library/LaunchDaemons

Question 6

What are the 3 primary user session stages in macOS Big Sur? What visual and audible cues do these stages provide?

Answer 6

• The login screen appears.
• launchd loads apps such as the Finder after user authentication.
• The user environment is active any time a user logs in to macOS Big Sur.

Question 7

What are the differences between launch daemons, startup items, launch agents, and login items?

Answer 7

The launchd process (with the process identification number of 1) launches all other system processes, including launch daemons and startup items, during Mac startup. When a user logs in, the launchd process running on behalf of the user account processes launch agents and login items.

Question 8

What are Safe Sleep, Standby, and Power Nap?

Answer 8

Safe Sleep and Standby are modes the Mac uses to reduce power usage and to safeguard data. When a Mac goes to sleep, it copies the entire contents of system memory to an image file on the system volume. This way, if your Mac stays in sleep mode long enough to completely drain the battery, no data is lost when your Mac has to turn off.
• Safe Sleep—Your Mac enters this mode if the battery becomes completely drained or if you leave your Mac idle for a long time. To wake your computer, restart your Mac as if it was shut down. All MacBook computers that are compatible with macOS Big Sur support this mode.
• Standby—Your Intel-based Mac enters this mode as a power-saving standby when it’s in sleep mode and completely idle for more than three hours. To wake your Mac, interact with the keyboard, trackpad, or mouse. You don’t need to restart your computer.
• Power Nap—Power Nap is a state that periodically runs updates while your Intel-based Mac is in sleep mode. The type of updated information varies depending on whether your Intel-based Mac is running on battery power or plugged into a power adapter.

Question 9

What happens during user logout?

Answer 9

During user logout, the user’s loginwindow process performs these actions:
• Requests that user apps quit
• Automatically quits user background processes
• Runs logout scripts
• Records the logout to the main system.log file
• Quits the user’s loginwindow and launchd processes

Question 10

What happens during Mac shutdown?

Answer 10

When a Mac shuts down, loginwindow logs users out and then tells the kernel to quit the remaining macOS Big Sur processes. Then the Mac shuts down.

Question 11

How do you start up a Mac with Apple silicon in safe mode?

Answer 11

For a Mac with Apple silicon, turn the Mac off. Then press and hold the power button until startup disks and Options appear. Press and hold the Shift key, then click Continue in Safe Mode.

Question 12

How do you start up an Intel-based Mac in safe mode?

Answer 12

For an Intel-based Mac, press and hold the Shift key during startup to initiate safe mode. Release the Shift key when you see the login window.

Question 13

For a Mac with Apple silicon, which keyboard shortcut can you use to temporarily choose another startup disk?

Answer 13

For a Mac with Apple silicon, turn the Mac off. Then press and hold the power button until startup disks and Options appear. Select your startup disk (with your pointer or with the Left arrow and Right arrow keys), then click Continue or press Return.

Question 14

For an Intel-based Mac, which keyboard shortcut can you use to temporarily choose another startup disk?

Answer 14

For an Intel-based Mac, press and hold the Option key during startup to open Startup Manager. Then you can temporarily choose another startup disk.

Question 15

What 3 changes are made when macOS Big Sur starts up in safe mode?

Answer 15

• Verifies your startup disk and, if there are issues, attempts to repair the system volume structure
• Deletes kernel cache and other system cache files
• Deletes font caches

Question 16

Which items aren’t loaded when macOS Big Sur starts up in safe mode?

Answer 16

When macOS Big Sur starts up in safe mode, it doesn’t load kernel extensions, 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.