Lesson 28: Troubleshoot Startup and System Issues

Question 1

What is the role of the Apple T2 Security Chip in a macOS Catalina startup?

Answer 1

The T2 Security Chip verifies every step of the boot process to ensure that the hardware and software haven’t been tampered with.

Question 2

What happens if your macOS with a T2 Security Chip identifies errors and experiences failures during the secure startup process?

Answer 2

If your macOS with a T2 chip identifies errors and experiences failures during the secure startup, then your Mac will enter macOS Recovery, Apple T2 Security Chip recovery mode, or Apple T2 Security Chip Device Firmware Upgrade mode (T2 DFU mode).

Question 3

What are the primary system initialization stages in macOS Catalina?

What visual and audible cues do these stages provide?

Answer 3

Each primary stage of system startup can be indicated by the following cues:

• Firmware: Power on. POST. Startup chime (depending on model).
• 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 4

What does the firmware do?

What’s the Power-On Self-Test (POST)?

Answer 4

The Mac firmware tests and initializes the Mac computer’s hardware and it locates and starts the Booter.

The POST checks for basic hardware functionality when a Mac powers on.

Question 5

What role does launchd serve during Mac startup?

Answer 5

launchd starts macOS Catalina processes.

It also manages macOS Catalina initialization and starts the loginwindow process.

Question 6

Name two locations launchd searches for preference files that control how LaunchDaemons are configured.

Answer 6

During macOS Catalina startup, launchd uses preference files for LaunchDaemons in the following locations:

1. /System/Library/LaunchDaemons
2. /Library/LaunchDaemons

Question 7

What are the primary user session stages in macOS Catalina?

What visual and audible cues do these stages provide?

Answer 7

Each primary stage of a user session can be indicated by the following signs:

• 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 Catalina.

Question 8

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

Answer 8

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 9

What are Safe Sleep, Standby, and Power Nap?

Answer 9

Safe Sleep and Standby are modes used by Mac that use very little or no power 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 just like it was shut down. All Mac notebook models that are compatible with macOS Catalina support this mode.
• Standby: Your Mac enters this mode as a power-saving standby when it’s asleep and completely idle for more than 1 hour or after 3 hours, depending on the manufacture date. To wake your Mac, interact with the keyboard, trackpad, or mouse. You don’t need to restart your computer. Newer Mac computers with flash or solid-state drive (SSD) storage use this mode.
• Power Nap: Power Nap is a state that periodically runs updates while your Mac is sleeping. The type of updated information varies depending on whether your Mac is running on battery power or plugged into a power adapter. Power Nap enablement varies by type of computer.

Question 10

What happens during user logout?

Answer 10

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 11

What happens during Mac shutdown?

Answer 11

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

Then the Mac shuts down.

Question 12

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

Answer 12

Hold down the <kbd>Shift</kbd> key during startup to initiate safe mode.

Question 13

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

Answer 13

Hold down the <kbd>Option</kbd> key during startup to open Startup Manager.

Then you can temporarily choose another startup disk.

Question 14

What changes are made when macOS Catalina starts up in safe mode?

Answer 14

Startup in safe mode performs the following permanent actions:

• 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 15

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

Answer 15

When macOS Catalina performs a startup 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
• Any user-specific launch agents