On an iPhone 8, or later:

Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then, press and hold the Side button until you see the recovery-mode screen.

On an iPhone 7 or iPhone 7 Plus:

Press and hold the Sleep/Wake and Volume Down buttons at the same time. Don’t release the buttons when you see the Apple logo. Keep holding both buttons until you see the recovery mode screen.

On an iPhone 6s and earlier or iPod touch:

Press and hold the Sleep/Wake and Home buttons at the same time. Don’t release the buttons when you see the Apple logo. Keep holding both buttons until you see the recovery mode screen.

进一步了解恢复模式的使用