Help! I Can't boot my mac pro from USB Thumb Drive With High Sierra

Calebe Souza

macrumors newbie
Original poster
Feb 10, 2020
Hello, I need help.

I accidentaly recovered Machintosh HD with the content of my thumb drive with installation of Mac OS High Sierra.

Now, when I try to boot from the USB (Turn the mac on with OPTION key), the thumb usb drive does not appear there, only the installation that is on old Machintosh HD.

So, when I try to erase, it doest let me do it because it can't be unmounted. I'm lost on what I can do now.

My mac is the last one with DVD Drive.

What can I do?


macrumors P6
Feb 20, 2009
Try this:
a. Reboot
b. IMMEDIATELY hold down "command-OPTION-R".
c. You will need your wifi password
d. This should boot to internet recovery (spinning globe icon). It will take some time.

Can you get this far?