Shutdown is one word, no hyphen, as a noun, and two words as a verb, to shut down.

Is shutdown one word or two?

Two words as a verb, one word as a noun. Use shut down to describe exiting the operating system and turning off the device in a single action. Don't use shut down to describe turning off a device or as a synonym for close. To turn off your computer, select Settings, and then select Shut down.

How do you write a shutdown?

To create a shutdown command that shuts the computer down immediately, type shutdown.exe -s -t 00 .