It will repairs errors that might prevent your Mac from booting. Among them, Disk Utility is the most useful tool. When the recovery system has booted, choose the option you need. Next, click the USB icon in the window to select it. Before the Apple logo appears, hold down Option and Command keys. To use the new recovery stick, you need to insert the USB hard drive again and reboot. Be patient and keep your USB hard drive connected firmly until it prompts to.

You need to ensure the action and click Continue, typing in the right password you have set for the Mac. When it finished for step 3, go to to download the Recovery Disk Assistant. The downloaded Recovery Disk Assistant will detect the USB drive. Click the Partition button in the dialogue. Click the drop-down list for the Format and select Mac OS Extended. Click Options, then click GUID Partition Table heading, then OK. In the Partitions Layout heading, select 1 Partition from the drop-down list. Select it, then select the Partition heading. When connected successfully, it should appear in the window or the Disk Utility window. Next, plug in your USB hard drive to the USB slot on your Mac, making sure it is connected with your Mac. It is in the Utilities folder under Applications. If you have some important files there, please move them to somewhere to store first.

Note: while using a USB memory stick to restore Mac, all data on the device will be erase completely.

Here are the 7 steps you need to know for how to restore Mac from External hard drive, including USB flash drive. And it is also an exclusive feature that Mac turns any removable storage device into a recovery tool. Restoring Mac from external hard drive on Mac is one of the choices that people apply if they can’t connect to a stable Wi-Fi while restoring a Mac. I want to restore Mac from an external hard drive. ' Is it possible to restore Mac from USB drive on Mac? I heard somebody said that but I don’t know the details. Updated to Troubleshooting Tips by William on | Approved by Anthony Spadafora

How to rebuild a mac pro