To help troubleshoot problems in OS X, Apple supports several alternative boot modes, the most common of which is safe mode. There's also a verbose mode that displays what background processes are being loaded, and a single-user mode to avoid user accounts and the OS X graphical interface. While these various modes can be useful, there are times that a system gets stuck loading them and won't boot normally.
These modes are triggered by a boot argument that is passed to the OS X kernel, which can be done in one of two ways. The first is to … Read more