Right off the bat I'll admit it was stupid to jump into trying to install a new version of OS X to the only partition without having taken adequate precautions (no backups or recovery disks), but unfortunately it's done. (the failed installation attempt, not the installation itself!)

I'm on a mid-2011 MBP that was running Lion. I download the installer for the latest OS X beta version to my HD and started installation process from there. The system rebooted and the installation started, but after 1 minute into the estimated 43 minutes for the installation to complete, I get an "Install Failed" message: "OS X could not be installed on your computer. The OS X upgrade couldn't be started because the disk Lion DP GM is damaged and can't be repaired. After your computer restarts, back up your data, erase your disk, and try installing again. Click Restart to restart your computer and try installing again."

Restarting just repeats the process and the same problem recurs. I went into "Disk Utility" from the Installer's menu, and trying to verify the offending volume returns "This disk needs to be repaired. Click Repair Disk". Unfortunately the "Repair Disk" option stays greys out.

Is there any way I can "revoke" the installation process (via the Terminal perhaps?) and get back to my previous set up with Lion (without losing data, obviously), so I can start over the right way this time?

Any advice is appreciated.


I'm not able to back up my main volume ("Lion DP GM") with Disk Utility. It barely starts before I get the following error:

Unable to create "Lion DP GM.dmg" (Input/output error)

I tried booting in recovery mode and reinstalling Lion, but it didn't work. Under the disk "Lion DP GM" where I would install it, it says

This disk is locked

When the OS installer is running, I can see - via Terminal - the contents of my main volume under /Volumes/Image Volume, whereas in Recovery Mode it's under /Volumes/Lion DP GM

Unless someone has some bright ideas how to restore things back to how they were, I would at least like to attempt backing up the entire "Lion DP GM" disk to an external disk via Terminal (since Disk Utility failed). What command would be the best way to attempt this?

Update #2:

In the end I copied just the bare essentials to an external drive via Terminal, which didn't cause any problems. Then I erased the whole partition, and did a USB installation, which completed successfully. Disk Utility on the new version of Mac OS X is no longer complaining of HD errors (although I'm not sure whether that means I'm in the clear or not).


2 Answers 2


If you haven't already made backups, you can start up from the recovery partition and save a disk image of the main OS X volume (or other volumes you use) to a different drive in Disk Utility.

The first thing I'd try would be to do an upgrade install of 10.7 by choosing Reinstall OS X without erasing anything first. If that wouldn't work, I'd do a clean reinstall and restore files manually.

See these Apple KB articles:

  • Thanks. I was thinking I ought to start by making a disk image of the main volume, and I'm glad you confirmed it. I'll probably do it later tonight... let's see how it goes.
    – Aky
    Jun 12, 2013 at 13:25

Since your install didn't complete, it's entirely likely you still have a Mountain Lion recovery HD and can simply wipe the entire drive and start over with Mountain Lion to ensure it's really a hardware issue (or rule out a hardware issue).

Just power it off, press the power button and hold the option key to boot into Recovery HD. From there you use Disk Utility to erase the entire drive (repartition it if needed). You could also connect the Mac to another computer in target disk mode and repair / erase the volume and then go back to recovery HD (or run Mountain Lion installer from a second Mac with yours still in target mode).

  • Unless I've misunderstood you, your primary suggestion will cause everything to be wiped everything clean - which is what I'd like to avoid, if possible. Also,I've been repeatedly unable to repair my volume (although I haven't tried the target disk mode suggestion - which would be a bit difficult to accomplish in my present circumstance.)
    – Aky
    Jun 12, 2013 at 22:18
  • Sadly, the fastest way to determine if you have a drive with a corrupt partition or other corrupt data is to erase/re-partition it. When you need to pause to get a backup or consider a tool that will repair things in place, that adds cost/delay/skills to the mix. Target mode is the simplest manner to just get the drive mounted and let another CPU/OS do the saving of files.
    – bmike
    Jun 13, 2013 at 12:58
  • I've erased the partition now (as I mention in my updated question), and managed to install Mavericks without further incident. Upon verification of the volume, Disk Utility in Mavericks now reports it to be OK. Does this mean I'm in the clear?
    – Aky
    Jun 13, 2013 at 19:22
  • Yes - you should be set. My expectation is the tool that had problems with the layout was free to fix them (or the clearing fixed the problems itself) once there wasn't data to protect.
    – bmike
    Jun 15, 2013 at 14:56

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .