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Cannot erase start up disk even when restarting using command R... Please help

I would like to erase my start up disk but when i restart and use command + R all options to erase are greyed out?? There is no option in the menu i can see to unlock the drive not sure whats going wrong here??

MacBook Air

Posted on Jul 4, 2015 2:23 PM

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6 replies

Jul 4, 2015 2:26 PM in response to sonia.

What do you mean by "when i restart and use command + R all options to erase are greyed out??" Are you booting from the Recovery HD? Did you open Disk Utility from the Utility Menu? Did you do this:


Install or Reinstall OS X from Scratch


Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.


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.


Erase the hard drive:


1. Select Disk Utility from the main menu and click on the Continue button.


2. After DU loads select your startup volume (usually Macintosh HD) from the

left side list. Click on the Erase tab in the DU main window.


3. Set the format type to Mac OS Extended (Journaled.) Optionally, click on

the Security button and set the Zero Data option to one-pass. Click on

the Erase button and wait until the process has completed.


4. Quit DU and return to the main menu.


Reinstall OS X: Select Reinstall OS X and click on the Install button.


Note: You will need an active Internet connection. I suggest using Ethernet if possible

because it is three times faster than wireless.


This should install the version of OS X that you had installed.

Jul 4, 2015 3:47 PM in response to sonia.

To completely erase the HDD:


Install OS X Using Internet Recovery


Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.


Boot to the Internet Recovery HD:


Restart the computer and after the chime press and hold down the COMMAND-OPTION- R keys until a globe appears on the screen. Wait patiently - 15-20 minutes - until the Recovery main menu appears.


Partition and Format the hard drive:


  1. Select Disk Utility from the main menu and click on the Continue button.
  2. After DU loads select your newly installed hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Click on the Partition tab in the DU main window.
  3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Click on the Options button, set the partition scheme to GUID then click on the OK button. Set the format type to Mac OS Extended (Journaled.) Click on the Partition button and wait until the process has completed. Quit DU and return to the main menu.


Reinstall OS X: Select Reinstall OS X and click on the Install button. Be sure to select the correct drive to use if you have more than one.


Note: You will need an active Internet connection. I suggest using Ethernet if possible because it is three times faster than wireless.


This should restore the version of OS X originally pre-installed on the computer. However, since the release of Yosemite it's likely you cannot install Mavericks.

Cannot erase start up disk even when restarting using command R... Please help

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