I'm trying to fix someone's Macbook, and I am a Windows user so I'm having trouble confirming that his hard drive is ruined or unfixable which is what I think is the problem.

When you boot it up it takes you to OS X Utilities, and when I try to press "Reinstall OS X", when prompted to select a disk to install OS X, the hard drive displays "This disk is locked." When I go into disk utilities and try to repair disk, I eventually get "live file system repair is not supported"

I assume this is a sign that the hard drive is failed and in need of replacement, but I'm looking to make sure there's nothing I can do to fix it.

Also, I know on Windows I could boot from a USB device or CD, (say I have Windows installed on a flash drive or a Ubuntu disk), and I'm wondering what my options are there if I don't want to just buy a new hard drive. I'd really like to be able to boot OS X from a flash drive and simply use that as the internal hard drive, is that at all possible?

  • Yours would be the conclusion I would reach as well, but you're in no way wrong to search for a simpler solution.
    – krs013
    Commented Sep 20, 2014 at 8:55

4 Answers 4


Start up the computer holding the option key, which takes you to the Startup manager; that will show you your boot options. It should show at least the recovery hd, possibly even the main drive. If the main drive is an option, select it, then before hitting enter, hold down both the Cmd key and the "S" key. That will boot you into single user mode, which should allow you to access the drive unhindered, outside of OS X.

A black screen will appear, followed by a bunch of text. At the end of the scrolling, follow the instructions listed.

At the prompt type the following then hit enter:

/sbin/fsck -fy

If there are errors, it will say the file system appears ok, but then there will be "the file system has been modified". If so, repeat the command until it just says the file system is ok.

Then at the command prompt, run

/sbin/mount -uw /

This mounts the root drive as writeable, and will remove damaged or unnecessary files. It may or may not tell you that some files have been removed. Regardless, at the next prompt, run reboot. Allow the system to restart unhindered. It may boot up into the main drive on its own then. If not, it will boot back into recovery, but you may have better luck in recovery now after repairing first in single user.


I recently had a similar issue. OS X has a "safety" feature where, if the system detects a problem with a volume, it can then set a flag in that drive's partition table that forces OS X to run "fsck" (a unix disk utility) on the volume before it can be mounted.

What I have observed is that if you are booted into the Recovery partition of that machine (or also I would guess, an OS X install drive), the corrupted volume will appear as "locked", as you are seeing. I have even had OS X Disk Utility tell me that the volume had a "hardware error" when, in fact, it did not.

Note that if you boot in target disk mode and attempt to mount the corrupt volume on another Mac, then what will happen (on 10.8.x or newer) is that instead of mounting the volume, OS X will run fsck in the background, although the user has no indication that is happening unless you look in Activity Monitor, and view All Processes (sort by CPU % for best results). Fsck can take its sweet time, 30-45 minutes on my 750 GB MacBook Pro! If you run Disk Utility or similar utilities like Disk Warrior during this time, since fsck is already running on that drive, then the other disk utility will report a hardware error, even though the hardware is fine.

However if you wait until fsck stops running silently in the background, OS X will eventually mount the drive in read-only mode, which is what you have observed as the volume being "locked".

What I did to fix it was boot the MacBook in target disk mode and connect it to my desktop Mac, then wait until fsck failed and the disk mounted as read-only. Then run TechTool Pro utility and scan for bad blocks, none found, hardware is perfect. Next run DiskWarrior and rebuild and replace the corrupt directory. Fixed.

You could also boot from a DiskWarrior recovery disk if you don't have another Mac. The TechTool Pro surface scan may be considered optional, unless you really want to rule out hardware failure.

I have had two drives recently where the Console logs showed i/o errors and other issues that you would think meant hardware failure, but at the end of the day it was caused by old, incompatible 3rd-party software. In one case, it was Google Drive that caused it, in another, an outdated copy Symantec PGP WDE. I would check all your Library/LaunchDaemons and LaunchAgents and any StartupItems and Extensions and Spotlight Plugins on all systems and make sure there are no outdated things lurking around. Apple's last three major OS X releases have ever-tightening security and sandboxing that has wreaked absolute havok on low-level hardware-related third-party stuff.


Certainly you can use a USB with OS X on it to boot from it.

You will have to create it first.

If you have a DVD drive with OS X you can use it as well to boot from.

Boot from (USB or DVD) can be activated with, pressing Option (alt) key during start up to select where to boot from.

If you are trying to repair the existing OS X on the HDD, then use the Internet Recovery option in the OSX Utilities. (cmd-r).

To check the hardware press "D" during start up, that should start the Apple Hardware test.


make partition of your hard disk using disk utility and then try

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