Tech Tip: ‘An Error Occurred While Preparing the Installation’ Fix

Having worked in Technical Support here at MacSales.com for some time now, I have helped customers handle many different types of errors and problems that they have come across. Some such as, “The disk you inserted is not readable by this computer,” might have simple solutions like formatting the disk, and some are more difficult such as “My Mac keeps freezing. Help!”

Related: My Upgrades tool helps you get the most from your Mac

One error that customers often come across while upgrading their machines occurs during the re-installation of OS X, and it has a relatively simple fix.

Once booted into the recovery partition and selecting “Reinstall OS X”, the “Eligibility Verification” window shows up. The error occurs as soon as you click “continue”. An unspecified error shows up which states “An Error occurred while preparing the installation. Try running this application again.” Upon doing so, the same exact error pops up. Nothing has been done to have this occur, so what exactly is going on?

Unspecified Error

While this can be frustrating, something quite simple is going on in the background that needs to be addressed. One of the checks that occur during “Eligibility Verification” is to see what time the machine thinks it is. If the computer is reporting the wrong time, an error will occur.

While there is a simple fix, it does require using the Terminal to accomplish. Many users might be wary of the Terminal, feeling like something could break and that it’s something only hackers and System Administrators use. While this can be true, the Terminal can be your friend and help you to resolve quite a long list of issues that commonly occur. But with great power comes great responsibility. Terminal can be destructive if its abilities are improperly used. My recommendation for those that are wary of this wonderful tool is to copy/paste commands or to type them very carefully and to double check what was typed before execution.

To fix the aforementioned “unspecified error”, follow the steps below:

  • First click “OK” on the error window.
  • Then click on “Utilities”, then “Terminal”.
  • Once opened type in “date” without the quotes and hit enter. This will give you the computer’s current time and date.
  • To fix the date, type in the current date/time in the following format: “date mmddHHMMyyyy”. (mm = two digit month, dd = two digit day, HH = 24 hour, MM = minute, yyyy = 4 digit year) So if it is currently 10:46am, June 19, 2015 the command would look like: “date 061910462015”.
  • Once you have the current date/time inserted, you will then hit enter. You can double check to see if it was set properly by using the “date” command once more, it should show the date/time you have just typed in (see image below).
  • Once the proper date and time is set on the computer. Exit the Terminal and run the OS X installer once more. This time it should go through without any errors! If it doesn’t, feel free to contact an OWC technician for further assistance.

Terminal Commands

More tech tips from OWC
If you’re looking to downgrade your OS from Yosemite to Snow Leopard, check out OWC Dan’s guide with step-by-step instructions.

And look for many more tech tips for your Mac or iDevice at the Rocket Yard!


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