NVRAM (nonvolatile random-access memory) is a small amount of memory that your Mac uses to store certain settings and access them quickly. PRAM (Parameter RAM) stores similar information, and the steps for resetting NVRAM and PRAM are the same.
Jul 09, 2020 Otherwise, you can select the Apple icon in the top-left corner of the screen and choose Restart. You can also use the keyboard shortcut Control + Command + Eject (or power button) if your computer. Step 3: Click the Apple logo in the top-left corner and select Restart on the drop-down menu. Step 4: Once your Mac restarts, press the Command + R keys together. Keep holding them until your Mac. When your Mac powers up, it normally uses the system on its internal hard drive unless you change this behavior by choosing System Preferences@@→Startup Disk. You can also change what your Mac does by holding down the following keys or key combinations during startup. Print these boot option keys, because they’re particularly helpful to have.
Settings that can be stored in NVRAM include sound volume, display resolution, startup-disk selection, time zone, and recent kernel panic information. The settings stored in NVRAM depend on your Mac and the devices that you're using with your Mac.
If you experience issues related to these settings or others, resetting NVRAM might help. For example, if your Mac starts up from a disk other than the one selected in Startup Disk preferences, or a question mark icon briefly appears before your Mac starts up, you might need to reset NVRAM.
How to reset NVRAM
Shut down your Mac, then turn it on and immediately press and hold these four keys together: Option, Command, P, and R. Apple ssd enclosure. You can release the keys after about 20 seconds, during which your Mac might appear to restart.
- On Mac computers that play a startup sound, you can release the keys after the second startup sound.
- On Mac computers that have the Apple T2 Security Chip, you can release the keys after the Apple logo appears and disappears for the second time.
If your Mac is using a firmware password, this key combination does nothing or causes your Mac to start up from macOS Recovery. To reset NVRAM, first turn off the firmware password.
Software to download music from website. When your Mac finishes starting up, you might want to open System Preferences and adjust any settings that were reset, such as sound volume, display resolution, startup disk selection, or time zone.
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- If you're using a desktop Mac instead of a notebook, and settings such as sound volume or time zone are reset every time you shut down and unplug your Mac, you might need to replace the battery inside your Mac. This small battery is on your computer's logic board, and it helps NVRAM retain settings when your Mac is unplugged. You can take your Mac to an Apple service provider to replace the battery.
- If you experience issues with sleep, wake, power, charging your Mac notebook battery, or other power-related symptoms, you might need to reset the SMC (System Management Controller).
To use any of these key combinations, press and hold the keys immediately after pressing the power button to turn on your Mac, or after your Mac begins to restart. Keep holding until the described behaviour occurs.
- Command (⌘)-R: Start up from the built-in macOS Recovery system. Or use Option-Command-R or Shift-Option-Command-R to start up from macOS Recovery over the Internet. macOS Recovery installs different versions of macOS, depending on the key combination you use while starting up. If your Mac is using a firmware password, you're prompted to enter the password.
- Option (⌥) or Alt: Start up to Startup Manager, which allows you to choose other available startup disks or volumes. If your Mac is using a firmware password, you're prompted to enter the password.
- Option-Command-P-R:Reset NVRAM or PRAM. If your Mac is using a firmware password, it ignores this key combination or starts up from macOS Recovery.
- Shift (⇧): Start up in safe mode. Disabled when using a firmware password.
- D: Start up with the Apple Diagnostics utility. Or use Option-Dto start up this utility over the Internet. Disabled when using a firmware password.
- N: Start up from a NetBoot server, if your Mac supports network startup volumes. To use the default boot image on the server, hold down Option-N instead. Disabled when using a firmware password.
- Command-S: Start up in single-user mode. Disabled in macOS Mojave or later, or when using a firmware password.
- T: Start up in target disk mode. Disabled when using a firmware password.
- Command-V: Start up in verbose mode. Disabled when using a firmware password.
- Eject (⏏) or F12 or mouse button or trackpad button: Eject removable media, such as an optical disc. Disabled when using a firmware password.
If a key combination doesn't work
If a key combination doesn't work at startup, one of these solutions might help: Apple store is still down.
- Be sure to press and hold all keys in the combination together, not one at a time.
- Shut down your Mac. Then press the power button to turn on your Mac. Then press and hold the keys as your Mac starts up.
- Wait a few seconds before pressing the keys, to give your Mac more time to recognise the keyboard as it starts up. Some keyboards have a light that flashes briefly at startup, indicating that the keyboard is recognised and ready for use.
- If you're using a wireless keyboard, plug it into your Mac, if possible. Or use your built-in keyboard or a wired keyboard. If you're using a keyboard made for a PC, such as a keyboard with a Windows logo, try a keyboard made for Mac.
- If you're using Boot Camp to start up from Microsoft Windows, set Startup Disk preferences to start up from macOS instead. Then shut down or restart and try again.
Remember that some key combinations are disabled when your Mac is using a firmware password.
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- Find out what to do if your Mac doesn't turn on.
- Find out about Mac keyboard shortcuts that you can use after your Mac has started up.