Single-user (-s/cmd-S)

• The firmware (either BIOS or EFI) initializes the hardware
• On BIOS machines, the screen is black and shows white text during this process
• On EFI machines, the screen is gray and shows nothing during this process (this applies to Intel Macs, other EFI machines might have other implementations)
• The boot loader is loaded by the firmware
• On BIOS machines, boot is loaded and a boot-132 message is shown
• On EFI machines, efiboot is loaded and an Apple logo but no spinner is shown (this applies to Intel Macs, other EFI machines might have other implementations)
• The boot loader reads /Library/Preferences/SystemConfiguration/com.apple.Boot.plist
• If the file is not present, the boot loader prints an error message
• The boot loader loads XNU and the kernel extensions (kexts)
• On BIOS machines, a spinning star or a list of kexts being loaded is shown
• On EFI machines, an Apple logo but no spinner is shown (this applies to Intel Macs, other EFI machines might have other implementations)
• XNU is loaded
• If the essential KEXTs (especially the Platform Expert, which is in AppleACPIPlatform.kext) were loaded successfully as well, the kernel starts and prints a copyright message mentioning University of California at Berkeley
• XNU loads KEXTs (for the first time; those with OSBundleRequired set to "Root") and waits for the root device
• If the root device can be accessed using the available kexts, the kernel prints the message "Got root device"; at some point thereafter the rest of the KEXTs are loaded (those without OSBundleRequired set to "Root")
• If the root device cannot be accessed using the available kexts, the message reads "Still waiting for root device..." instead
• The kernel starts /sbin/launchd on the root device
• launchd starts /bin/launchctl
• launchctl starts /bin/bash

• ...