Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.


macrumors newbie
Original poster
Feb 21, 2017
I have a silver Macbook Pro. Not sure of the exact model, it has a 250GB HDD and a DVD drive. I am having issues reinstalling Mac OS. I have reset many Mac computers and never seen this issue.

I tried via USB. I plug in the USB (I have 2, 1 with El Capitan and 1 with Mavericks) When I hold down Option during boot, it won't go to the drive select. I goes straight to MacOS Recovery.

I tried holding down Option, Command, + R to go into internet recovery. It won't load that either.

I tried resetting the PRAM, by holding P, R, Command, and Option till it's supposed to do the Mac start up chime. It never does, just goes to MacOS Recovery.

Inside Mac OS recovery I try to format the top drive. It gives me an error, couldn't unmount the drive. I tried repairing, it found no issues. I tried a few different terminal commands from various guides I looked up, nothing is working.


macrumors 6502
Dec 12, 2015
Some of this sounds like you might have an issue with the keyboard. However, in recovery when it says you can’t unmount, it’s probably due to either heavy partition corruption or something hardware related. I’ll assume it isn’t hardware related, but if what I give you doesn’t work, I would lean towards hardware.

Let it go to recovery and open terminal. Type ‘diskutil unmountdisk force disk0’ and hit enter, don’t include the ‘ ‘. If you get an error try this. Type ‘ps -ax | grep fsck’ and hit enter. You will always get one result for the search for fsck it’s self. If you get another longer line that contains something like /dev/disk0s2 blah blah, note the PID associated with it, and then type ‘kill xxx’ where xxx is the PID. Now try forcing the unmount again. If it still fails, I’d lean very hard towards hardware issue.

If you manage to unmount the drive or kill fsck and unmount the drive, then do ‘diskutil zerodisk disk0’ and let the drive start to zero. Running this for just a few seconds is fine as it is more than enough to nuke the partiion map.

Now quit terminal and use disk utility to format the drive and proceed as you normally would.


macrumors Penryn
Feb 20, 2009
MacBook Pros 2009 and earlier can't do internet recovery at all.
SOME (but not all) 2010 MBP's can do internet recovery. Depends on firmware.
2011 and later MBP's CAN do internet recovery.

Having said that...
- Could it be a problem with the internal drive itself?
- Could it be a problem with the drive ribbon cable?

What you might try:
1. Take the internal drive OUT OF the MBP and connect it with an adapter/dongle
2. Try to boot from the USB installer now

Another thought?
What size is the display of the MBP?
Is it 15" or 17" by any chance?
This could be important information, due to the "RadeonGate" issue for 2011 MBP's 15" and 17" ...


macrumors newbie
Original poster
Feb 21, 2017
Tried using an external usb keyboard?
I got my hands on an Apple Magic Keyboard 2. Plugged it in via USB and did the PRAM reset with no issues and was able to hold down Option to boot from a USB to reinstall MacOS. The laptop's keyboard works otherwise.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.