Unlocking a Mac Without the Install Disc

by Tony Gamble

So you’ve scored yourself a new-to-you Mac from your favourite thrift shop, Kijiji, Craigslist or Used”insert-region-here”.com. You’re excited to get it home and test it out. You power it up, hear the glass-shattering BONG! noise associated with an Apple computer’s power-on routine, and yes, you make it to the login screen. Old iMac at Login Screen

Wait. Login screen? Asking for a password you can’t possibly know. Of course, if you have a disc containing the Mac OS X operating system, it’s a simple matter of popping it in and restarting to that (hold the Option key immediately after powering up to see a choice of startup drives). Then you can erase the hard drive and start fresh, as well you should. Without this option, however, you’re not out of luck.

There are three simple commands you can use to trick the Mac into thinking it hasn’t completed setting up OS X yet. To enter these, you need to start-up in what’s called Single User Mode. After powering on the computer, hold down the Command key and the ’S’ key at the same time. Keep holding this key combo until you see a black screen filling with lines of text that looks a lot like the old MS-DOS days. You can let go of the keys now, but wait until these startup dialogues end with a prompt that shows root#, following by the blinking cursor. Now enter the following three commands, pressing Return at the end of each:

mount -uw /
rm /var/db/.AppleSetupDone
shutdown -h now

When the computer reboots it will no longer bring you to the login screen because you’ve just removed the variable that tells OS X that setup is done. Instead, you should be presented with the last leg of the operating system’s install wizard where you are required to choose a language, username, password, etcetera. This means you can now login as a new admin user.

Mac OS X Right-Click Menu

Right-click on the user’s top-level folder to change permissions.

Of course, this doesn’t immediately give you access to the previous user’s files, which are locked behind that user’s password. There’s a workaround for that, too, which is why I heartily recommend wiping or removing a computer’s hard drive before reselling. Navigate to the previous user’s folder and right-click on it. From the menu, choose Get Info. At the bottom right corner, click the golden lock icon to unlock it. It’ll ask for your own password. Now you have access to the Sharing & Permissions section (click to twirl the arrow down if you can’t see the details). Click the ‘+’ icon in the bottom right corner to add a new user and when the choices pop up, select Administrators. When that has been added to the Sharing & Permissions list, click next to it to change the privileges to Read & Write. Drop the menu next to the cog icon, select Apply to enclosed items and voilà! You can now access and modify the files on the previous user’s account. With the exception of files secured behind FileVault, of course.

I hope you’ve found this tip helpful. Watch for more tips, trick and how-to’s every Friday, and if you have a tip that you’d like to share or a request, feel free to let us know in the comments section below.

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