Wiping iMac clean

[Jeffpatey]

I just traded my MacBook pro for a 2009 iMac. Its currently running Mavericks but they previous owner's stuff is still on it. I want to wipe the iMac clean and reinstall a new copy of OS X. I dont have the disk for the operating system. When i tried to erase the disk through the disk utility, it came up that it was unable to unmount the disk.

Also, i purchased mountain lion on my apple ID so i was wondering if when i reinstalled OS X if it would be possible without the disk. Thanks.
iMac, iOS 7.0.3

 

[Weaselboy]

What OS version is on the iMac now? If you are on Snow Leopard 10.6.6 or later you can login to the App Store app and get Mavs free under your own AppleID then make yourself a USB key installer for Mavs and do a fresh install that way.

 

[Jeffpatey]

Mavericks is currently on there. The main problem I have is that I want to wipe the Mac clean before I install a fresh copy but when I try to erase it says the disk cannot be unmounted

 

[blueroom]

Boot from the recovery partition <option+r>, delete the OSX partition & reinstall Mavericks.

 

[Jeffpatey]

And also I tried just reinstalling a fresh copy of mavericks but It says the disk is locked when I try

----------

I tried to delete the OS X partition but it keeps coming up that the disk cannot be unmounted and it won't work

 

[Weaselboy]

Mavericks is currently on there. The main problem I have is that I want to wipe the Mac clean before I install a fresh copy but when I try to erase it says the disk cannot be unmounted

And also I tried just reinstalling a fresh copy of mavericks but It says the disk is locked when I try

----------

I tried to delete the OS X partition but it keeps coming up that the disk cannot be unmounted and it won't work

Sorry I missed your last post. I hope you can still boot up and get to the App Store to obtain Mavs under your AppleID, or you will be a bit screwed here.

Tell me if you can still login under Mavs or not as that will dictate what we need to do next.

 

[Jeffpatey]

Yes I can still login to the Mac App Store on the iMac

 

[Weaselboy]

Yes I can still login to the Mac App Store on the iMac

Okay good. Go here in the app store and purchase Mavericks under your own AppleID. It is a free "purchase". This way when you go to install later you can use your own Apple ID. After you make the purchase go to the Purchases tab in the App Store app and stop the download.

When you go that disk locked message what exactly were you doing in Disk Utility? You should be able to command-r boot to the recovery screen then in Disk Util select the Macintosh HD partition only then click erase on the right side. Can you do that, or is that when you get the locked message?

Open Terminal and enter "diskutil list" without the quotes then post up the output here. That will show us if you have an encrypted partition or something causing this.

Look in the Security pane of System Prefs and make sure Filevault is not turned on.

 

[Jeffpatey]

when i get to the recovery screen, which disk do i select? "mac" or "recovery-10.9"?

 

[Weaselboy]

when i get to the recovery screen, which disk do i select? "mac" or "recovery-10.9"?

By default the one you want to erase is called "Macintosh HD". Perhaps the previous user renamed it Mac. You don't want to erase the recovery one (it actually won't let you). You can tell you have selected the correct one by the size. Click the Mac one and look at the lower right of Disk Utility and you should see a capacity listed of something close to the size of the drive. Click the recovery one and you should see that it is only 650MB.

This is odd though, because normally that recovery partition is hidden in Disk Utility. I bet the previous user was on some of the beta versions of Mavericks and was messing around with partitions.

Do you happen to have a USB key around? If you have one that is at least 1GB, it would be a good idea to make a backup of the recovery startup on the USB key using this tool from Apple. This way if your whole drive gets borked by this we can at least use that USB key to get you back in business.

 

[Jeffpatey]

ok ill do that! here is what i get when i try to erase the disk:

 

[Weaselboy]

ok ill do that! here is what i get when i try to erase the disk:

Confirm you are doing this while booted to the recovery partition after a command-r boot? It looks like from your photo you are selecting the disk itself. You want to select (click) where it says "mac" just below that and then try the erase.

 

[Jeffpatey]

i have another issue. Im trying to make a recovery disk on the USB and i need the administrators name and password to allow it and i dont know what that is.

 

[Weaselboy]

i have another issue. Im trying to make a recovery disk on the USB and i need the administrators name and password to allow it and i dont know what that is.

It is the same username and password you used to login to the computer when you start it.

 

[Jeffpatey]

it doesnt work. i had the username and password that they had to login but when i try it in the administrator is doesnt work

 

[Weaselboy]

it doesnt work. i had the username and password that they had to login but when i try it in the administrator is doesnt work

Okay. Reboot to the recovery screen by doing a command-r boot. Then in the Utilities menu start Terminal and the in "resetpassword" (without the quotes and make it all one word). A box will come up where you can select the admin account then reset the password to whatever you want. Then reboot and you can use the new password with the admin account you selected.

 

[Jeffpatey]

I have successfully made the recovery disk, so im going to try now and erase the disk again

----------

ok the erase worked! what do i do next?

 

[Bruno09]

Quit Disk Utility and in the OS X Utilities window, choose "Reinstall OS X".

(I assume you do not have a bootable installer, right ?).

 

[Weaselboy]

I have successfully made the recovery disk, so im going to try now and erase the disk again

----------

ok the erase worked! what do i do next?

Yep... just click Reinstall OS X like Bruno said. Be prepared to wait while it downloads the 5GB OS over the Internet. I find it helps to drink a beer while this is happening.

 

[Jeffpatey]

It all worked perfect! thanks for everything guys!