To get around that problem, hold down the Command + R keys when you turn on your Mac and let go when the logo appears. If you want to format your Mac's system drive, you can't do that when the Mac is running normally because the drive is in use by the operating system. Usually, you'll want ExFAT, which is the default for the MacOS. Select the drive you want to format and then choose “Erase.” Dave Johnson/Business InsiderĤ. At the top of the window, click 'Erase.'ĥ. In the pop-up window, choose the file system you want to use.
