Hard Reset Mac Os X

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Nov 18, 2019 Turn your Mac on. Immediately press and hold the command + option + P + R keys. Continue to hold the command + option + P + R keys for a minimum of 20 seconds; longer is fine but not necessary. After 20 seconds, you can release the keys. Aug 28, 2014 Mount the internal hard drive with write permission Remove the Mac setup file. This is the file that OS X checks to determine if the system is already set up.

Last week I needed to restore six MacBooks to their factory defaultsettings, deleting all data, accounts, network settings, and so on.Here’s the procedure I used. It results in a pristine Mac hard drive,right down to the multilingual welcome message and setup assistant toget started. If you’re getting ready to sell an old Mac, I recommendfollowing these steps to give the buyer as much of a new Mac experienceas possible, while also protecting your personal data from strangers.

None of this is new information necessarily, but unfortunately many ofthe support discussion boards that will be among the first results in asearch provide a great deal of misinformation, and some steps will varydepending on whether you’re restoring to Mac OS X 10.5 or 10.6. This isan attempt to bring everything to one page (and document for my ownfuture reference).

What you’ll need:

  • A Mac in need of hard drive resetting.
  • A little bit of Mac know-how—we’ll be digging into DiskUtility to erase the hard drive, single user mode, and root access.If any of this scares you, stop now and ask somebody for help.
  • Installer discs for the software you wish to restore. I had Mac OS X10.5 (Leopard) and the included Applications installer for theseMacBooks. These laptops actually shipped right as 10.6 (SnowLeopard) hit the shelves, so an extra installer disc for that wasincluded. I wound up installing it, too.
  • A second Mac, an external hard drive, a Firewire cable, and diskcloning software, if you wish to image the pristine hard drive foruse with other restorations (optional)
  • A wired Internet connection, to speed up large downloads a bit(optional)
  • Time. Depending on how securely you’re reformatting the hard drive,and how many updates you need to download, resetting a singlecomputer can take several hours.

The steps:

Boot the Mac from the installer disc. To do this, start your Macwhile holding down the C key on your keyboard. Insert the disc to boot.In a few minutes you should see the language selection screen for theMac OS X installer. Select your preferred language to continue.

Erase your hard drive. Select Disk Utility from the Utilities menuand select your hard drive. Note that secure reformatting techniques canbe very time-intensive. I went with the Zero Out Data option, which tookabout 40 minutes to complete on a 160 GB hard drive.

Install your operating system. If you’ve ever installed a fresh copyof your operating system, this step should feel pretty straightforward.Complete the steps to install Mac OS on the computer, using defaultsettings. I skipped the disc installer validation step because I knew mydisc did not have any problems, but if you want the extra sense ofsecurity plan on letting this step run for awhile.

Enable the root user. When the operating system installer is done,restart your computer, but boot it again from the installer disc byholding down the C key on your keyboard during startup. If youaccidentally boot from the hard drive, wait for the welcome video toplay through, then press command-Q to quit the installer and shut downyour computer. Start up again while holding down the C key to retrybooting from the installer.

Select your language again, then under Utilities choose the ResetPassword tool. Select the System Administrator (root) account and assignit a temporary password. You’ll just be using this during setup, andthis password will be removed before you’re done. Write the passworddown, if necessary; you’ll need to enter it several times as you installupdates to the operating system and any other software you install.Click Save, then quit the Reset Password tool.

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Reboot in single user mode. At this point you should still be bootedfrom the installer disc. Restart your computer, and this time hold downcommand-S to boot into single user mode. If you’re not used to seeingyour Mac’s Unix guts, this step can feel daunting. You’re going to entera few commands here to trick the Mac into thinking it’s all set up, andthus not try to walk you through the setup assistant each time.

When you see the % prompt followed by a cursor, begintyping the following. Do not type the % that startseach line—I’ve included it for context. Press return aftercarefully typing each line to process that command.

After typing the last command, your computer should begin booting in amore familiar fashion. In a moment you’ll see a login screen. Use theSystem Administrator account. The username will be root,and the password will be what you set in the Reset Password utility afew moments ago.

Make any network connections you’ll need to download software updates atthis time. Again, these are just temporary and will be removed by theend of the procedure. (If I had this to do over, I would have moved myoperation next to my router and plug in directly to an Ethernet port fora bit of a speed boost over my 802.11n wireless connection.)

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Install software from the Applications Installer disc. If youhaven’t done so already, you can eject your operating system installerdisc (don’t put it away yet; you’ll use it again in a bit). Insert theApplications Installer disc that was included with your Mac. This discprobably includes at least the iLife software bundle, which is includedon new Macs but does not get installed with the regular operatingsystem. Run the installer as normal. You probably will not need toreboot afterward, but if you do let the computer boot to the loginscreen and log in again as root to continue. You can ejectthe Applications Installer disc when done with this step.

Run software updates. Strictly speaking, this is an optional step.You can skip it if you want to leave the hard drive as it was when youfirst opened your Mac. I opted to bring everything up-to-speed,including the operating system itself and the bundled iLife software.(Specifically, I updated the version of iLife that came with thecomputer; I didn’t install the paid upgrade to iLife ’11.)

Run Software Update (under the Apple menu) to download and installavailable updates for the computer. You’ll probably need to do thisseveral times, as some updates are dependent on others. You’ll also needto restart your computer at least a couple of times, logging in eachtime using the root user. This will probably be the mosttime-intensive step of the process. On my high-speed cable Internetconnection, I spent at least an hour downloading and installing updatepackages.

Once Software Update tells you your computer has no updates at thistime, you’re in the home stretch.

Re-enable the setup assistant and welcome video. You’ll need to getback into your Mac’s command line one more time, but this time you canjust use Terminal. It’s located in Applications > Utilities.Open Terminal and carefully type everything following the #:

Press return to process. What you’ve done is remove a file that your Maclooks for to see whether you’ve completed the Setup Assistant or not.You can quit out of Terminal now.

Re-disable the root user. Launch Directory Utility. This utility hasbeen moved from its old home in Applications > Utilities; nowyou’ll need to open the top level of your hard drive and navigate toSystem > Library > Core Services > Directory Utility (thisdirectory is not searchable in Spotlight). If necessary, click thepadlock and enter your temporary root password to make changes. Underthe Edit menu, select Disable Root User. Quit out ofDirectory Utility.

Reset the root user. Insert the Mac OS X installer disc, ifnecessary, and boot from it once more. Under the Utilities menu, selectReset Password. Select the root user and press the Resetbutton to remove network settings, among other things that are no longerneeded.

Check your work. Restart the computer from the hard drive you’vejust reset. Hold down the mouse button to eject the installer media andboot from the hard drive. If all went according to plan, you should seethe Mac OS X welcome video, followed by the first step of the setupassistant. Press command-Q to quit the assistant and shut down your Mac.Congratulations, your Mac’s hard drive looks brand new!


Cloning (optional)

If you need to restore several computers, as I did, I strongly recommendcloning the hard drive in the computer you just restored to the othercomputers. I did this using a second Mac (not one I was restoring), anexternal hard drive, and SuperDuper! backup software, connecting therestored MacBook to my second Mac via a Firewire cable and starting therestored Mac in target disk mode. I’m sure there are countless otherways I could have done this. Cloning and other backup techniques arebeyond the scope of this article, though I’ve included a few links inthe references section below.


  • Securely wipe your harddrive(Macworld)
. Questions or comments? Let me know what you think.

Start up from macOS Recovery

Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:

Apple silicon

Turn on your Mac and continue to press and hold the power button until you see the startup options window. Click the gear icon labeled Options, then click Continue.

Intel processor

Make sure that your Mac has a connection to the internet. Then turn on your Mac and immediately press and hold Command (⌘)-R until you see an Apple logo or other image.

If you're asked to select a user you know the password for, select the user, click Next, then enter their administrator password.

Reinstall macOS

Select Reinstall macOS from the utilities window in macOS Recovery, then click Continue and follow the onscreen instructions.

Follow these guidelines during installation:

  • If the installer asks to unlock your disk, enter the password you use to log in to your Mac.
  • If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
  • If the installer offers you the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.
  • Allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.

After installation is complete, your Mac might restart to a setup assistant. If you're selling, trading in, or giving away your Mac, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.

Other macOS installation options

When you install macOS from Recovery, you get the current version of the most recently installed macOS, with some exceptions:

  • On an Intel-based Mac: If you use Shift-Option-Command-R during startup, you're offered the macOS that came with your Mac, or the closest version still available. If you use Option-Command-R during startup, in most cases you're offered the latest macOS that is compatible with your Mac. Otherwise you're offered the macOS that came with your Mac, or the closest version still available.
  • If the Mac logic board was just replaced, you may be offered only the latest macOS that is compatible with your Mac. If you just erased your entire startup disk, you may be offered only the macOS that came with your Mac, or the closest version still available.

You can also use these methods to install macOS, if the macOS is compatible with your Mac:

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  • Use the App Store to download and install the latest macOS.
  • Use the App Store or a web browser to download and install an earlier macOS.
  • Use a USB flash drive or other secondary volume to create a bootable installer.