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I've downloaded Mac OS X Mountain Lion today and wanted to backup the installation image to a USB drive for later.

I've created a new empty partition of at least 8 GB size on the external drive using Disk Utility, and tried to restore the InstallESD.dmg image to this new partition, via the Restore menu.

However, doing that, I get the following error message, right after it finishes copying:

Cannot Allocate Memory

What can I do now?

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1 Answer 1

up vote 3 down vote accepted

It could be that there is a checksum mismatch for the disk image, or you experienced a bug in Disk Utility.

You can try to use the asr command-line utility to copy the image yourself. To do that, you need:

  • The InstallESD.dmg image
  • A large enough HFS+ partition on an external drive created through Disk Utility, let's call it Install
  • A running terminal

In your terminal, enter the following line, but replace the path to your OS X installer image and the target partition:

asr restore --source Desktop/InstallESD.dmg --target /Volumes/Install

Now, you should get output similar to the following:

Validating target...done
Validating source...done
Retrieving scan information...done
Validating sizes...done
Copying    ....10....20....30....40....50....60....70....80....90....asr: did not copy blessed information to target, which may have missing or out-of-date blessed folder information.
Ejecting the source image...done

Now, you can boot into the installer from your USB drive too. To verify if it worked, go to System Preferences » Startup Disk, and check if your installer appears:

enter image description here

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