28. Troubleshoot Startup and System Issues

Question 1

1. What are the primary system initialization stages in macOS High Sierra? What visual and audible cues do these stages provide?

Answer 1

1. Each primary stage of system startup can be indicated by the following cues:
   a. Firmware—Power on. Power On Self Test (POST). Startup Chime (depending on model).
   b. Booter—The booter process starts. The Apple logo is displayed in the center of the main display.
   c. Kernel—Kernel startup. The progress bar is displayed.
   d. System launchd—Starting other items. The Apple logo is replaced with login window.

Question 2

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

Answer 2

2. 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 3

3. What role does launchd serve during Mac startup?

Answer 3

3. launchd is responsible for starting macOS High Sierra processes. It also manages macOS High Sierra initialization and starts the loginwindow process.

Question 4

4. Which items are automatically started by launchd during Mac start up?

Answer 4

4. During macOS High Sierra startup, launchd starts these daemons and scripts:
   • /System/ Library/LaunchDaemons
   • /Library/LaunchDaemons

Question 5

5. What are the primary user session stages in macOS High Sierra? What visual and audible cues do these stages provide?

Answer 5

5. Each primary stage of a user session can be indicated by the following signs:
   a. The login screen displays.
   b. launchd loads apps, such as the Finder, after user authentication
   c. The user environment is active any time a user logs in to macOS High Sierra

Question 6

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

Answer 6

6. The administrator account launchd process launches Launch daemons and startup items during Mac start up. User account launchd processes launch agents and login items during user environment startups.

Question 7

7. What are Safe Sleep and Power Nap?

Answer 7

7. When a Mac battery drains, Safe Sleep saves the macOS High Sierra state to permanent storage. Power Nap enables a Mac to automatically wake in low-power mode. This enables the Mac to perform app and macOS High Sierra updates.

Question 8

8. What happens during user logout?

Answer 8

8. During user logout, the user’s loginwindow process performs these actions:
   a. Requests that user apps quit
   b. Automatically quits user background processes
   c. Runs logout scripts
   d. Records the logout to the main system.log file
   e. Resets device permissions and preferences to their defaults
   f. Quits the user’s loginwindow and launchd processes

Question 9

9. What happens during Mac shutdown?

Answer 9

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

Question 10

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

Answer 10

10. Hold down the Shift key during startup to initiate safe mode.

Question 11

11. Which keyboard shortcut can you temporarily use to choose another startup disk?

Answer 11

11. Hold down the Option key during startup to open Startup Manager. This enables you to temporarily choose another startup disk.

Question 12

12. Which changes are made when macOS High Sierra starts up in safe mode?

Answer 12

12. Startup in safe mode performs the following permanent actions:
    a. Attempts to repair the system volume structure
    b. Deletes system third-party kernel extension (KEXT) caches
    c. Deletes font caches

Question 13

13. Which items aren’t loaded when macOS High Sierra starts up in safe mode?

Answer 13

13. When macOS High Sierra performs a startup in safe mode, it doesn’t load 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.