Sometimes you need to debug OS X. See exactly what’s going on in the boot process. Or you may just be tired of the GUI (even I, a devout Cocoa addict, can get tired of it) and want to have a good old Command-Line/Shell OS. This is surprisingly easy to do. (This guide only applies to Intel Architecture Systems, which do not have a FileVault Encryption or a Firmware Password enabled.)
At Boot Up (before the chime) Hold:
Shift + CMD + S
(release a few seconds after chime)
The Bootloader will run, and then the system will begin to start in Verbose mode.
at the prompt: check and mount the system and run the launch daemon:
# /sbin/fsck -y
(This checks the system, is not necessary at all, it’s only done for safety reasons. Though it can take a while. Skip it if you’re feeling lucky.)
# /sbin/mount -wu
Now the System is mostly loaded… much of the OS is now available to you. Though you should run the launch daemon for full system capabilities.
Congratulations… now you have the full Operating System loaded in Single-User Mode, running BASH. This, ladies and gentlemen, is actually Darwin, not OSX (since OSX = Darwin + Cocoa GUI), Apple’s OpenSource BSD Operating System based on the XNU kernel. If the program runs in the Command-Line… it will run here.
remember these important commands:
# shutdown now
shutsdown the computer
# reboot now
reboots the computer
(read the man pages for these for a good chuckle)
Enjoy this Hack!
(Note: The SystemStarter daemon does not seem to work well on some machines, though most programs will run with out this daemon)