After running this command, when connecting an external monitor, the internal display will be disabled, which can be beneficial in some situations such as those where you are mirroring your desktop but wish to run the external display at a higher resolution than your laptop can run. This reverses the 'Clamshell' mode for Apple's laptop systems, where when you close the display but connect the system to an external monitor and keyboard the system will stay awake. These three options are the most common ones that people would use when troubleshooting their systems however, there are a number of others you can use as well: This command will boot the system into Single User mode without needing to hold Command-S at startup. This command will have the system always boot into Safe Mode. This command will set the system to always boot to Verbose mode, so you do not have to hold Command-V at startup. Apple's machines have a number of hidden boot options that you can use, though do keep in mind that most of these are for troubleshooting purposes and will only be useful to programmers.

In addition to keyboard commands at startup, you can use the 'nvram' terminal command to set a number of different boot options, which might be useful when troubleshooting your Mac. For instance, a common option is to hold the Shift key to boot to Safe Mode, but you can also hold Command-V for verbose mode (a text output of items as they load), or Command-S for Single User mode, which drops you to the command line as the 'root' user so you can perform troubleshooting tasks. When you boot a Mac system you have the option to supply keyboard commands at startup to boot the system to alternate environments.

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