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To completely securely erase an iMac with Yosemite

I want to completely Erase a 2008 refurbished 1TB iMac, but something has gone wrong.

In Disk Utility It shows 1TB capacity with 500GB available.

I when to Erase and after hours of processing it Still shows the same capacity and available. I used the most secure Erase, but the loaded apps and programs are still present.


Under Erase the only active option is Erase Free Space & I set a Most Secure (with 7 overwrites). It again shows "Erase Free Space" even when slider is at Most Secure -- which looks exactly the same as the option I used yesterday that did nothing to remove used items.


What am I doing wrong?

Posted on Mar 11, 2015 7:11 PM

Reply
6 replies

Mar 11, 2015 7:19 PM in response to pwwwayne

Clean Install of Snow Leopard


1. Boot the computer using the Snow Leopard Installer Disc or the Disc 1 that came

with your computer. Insert the disc into the optical drive and restart the computer.

After the chime press and hold down the "C" key. Release the key when you see

a small spinning gear appear below the dark gray Apple logo.


2. After the installer loads select your language and click on the Continue

button. When the menu bar appears select Disk Utility from the Utilities menu.

After DU loads select the hard drive entry from the left side list (mfgr.'s ID and drive

size.) Click on the Partition tab in the DU main window. Set the number of

partitions to one (1) from the Partitions drop down menu, click on Options button

and select GUID, click on OK, then set the format type to MacOS Extended

(Journaled, if supported). Optionally, click on the Security button and set the

Zero Data option to one-pass. Click on the Apply button.


3. When the formatting has completed quit DU and return to the installer. Proceed

with the OS X installation and follow the directions included with the installer.


4. When the installation has completed your computer will Restart into the Setup

Assistant. After you finish Setup Assistant will complete the installation after which

you will be running a fresh install of OS X. You can now begin the update process

by opening Software Update and installing all recommended updates to bring your

installation current.


5. If you are planning to sell or give your computer away, then do the following:


After you reformat your hard drive and reinstall OS X, the computer restarts to a

Welcome screen and asks you to choose a country or region. If you want to leave

the Mac in an out-of-box state, don't continue with the setup of your system. Instead,

press Command-Q to shut down the Mac. When the new owner turns on the Mac,

the Setup Assistant will guide them through the setup process.


Mar 12, 2015 11:34 AM in response to Kappy

Thank you for reply!


I didn't make myself clear. This iMac already has Yosemite OS X 10.10.2 installed and I don't have an installation disk of any version. (I do have TechTool & Disk Warrior but I don't know if they have an Erase option.)


I now see that to Erase I have to start-up from a different HD (which I do have but forget password)!

Mar 12, 2015 11:41 AM in response to pwwwayne

If it's the admin password you cannot remember then see the following. However, this won't help you if you need to start the computer using an installer disc to fix the problem:


Forgot Your Account Password


For Lion, Mountain Lion, or Mavericks


Boot to the Recovery HD:


Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.


When the menubar appears select Terminal from the Utilities menu.

Enter resetpassword at the prompt and press RETURN. Follow

instructions in the dialog window that will appear.


Or see:


Reset a Mac OS X 10.7 Lion Password

OS X Mountain Lion- Reset a login password,

OS X Mavericks- Solve password problems,

OS X Lion- Apple ID can be used to reset your user account password.


For Snow Leopard and earlier with installer DVD


Mac OS X 10.6- If you forget your administrator password,

OS X- Changing or resetting an account password (Snow Leopard and earlier).


For Snow Leopard and earlier without installer DVD


How to reset your Mac OS X password without an installer disc | MacYourself

Reset OS X Password Without an OS X CD — Tech News and Analysis

How To Create A New Administrator Account - Hack Mac

To completely securely erase an iMac with Yosemite

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