If you've encountered a problem with macOS, the solution might be to reinstall the system on your Mac. This can be done by any Mac owner, but it can be a little bit complicated. You'll need to put your Mac into macOS Recovery, which gives you tools to diagnose problems on your Mac, as well as reinstall the operating system.
- Reinstall Mac Os X Recovery Partition
- Boot Into Os X Recovery Partition
- Install Os X From Recovery Partition
Here's how to reinstall macOS using Recovery mode.
Entering macOS Recovery
macOS Recovery has tools at its disposal that allow you to diagnose problems with your Mac's hard drive, reinstall macOS, and restore from a Time Machine backup. You can enter Recovery by pressing certain key combinations. The combination you choose will determine which version of macOS will be installed on your system when you select Reinstall macOS.
- Press Command - R to install the latest version of macOS that was installed on your Mac without installing a later version.
- Press Options - Command - R to upgrade to the latest version of macOS that's compatible with your Mac.
- Press Shift - Option - Command - R to install the version of macOS that came with your Mac, or the version closest to it that's still available.
How to check your startup disk with Disk Utility in macOS Recovery mode
The first thing you'll want to do is make sure your Mac's startup disk is healthy. You'll need to use Disk Utility to do that.
- Click Disk Utility when in macOS Recovery.
- Click Continue.
- Click on your Mac's startup drive in the Disk Utility sidebar. It should be the drive at the top of the sidebar if there are multiple drives.
- Click First Aid.
- Click Run. First Aid will run, checking the health of your Mac's drive. This process could take a little while.
- Click Done.
- Click Disk Utility in the Menu bar.
- Click Quit Disk Utility.
How to erase your startup disk in macOS Recovery mode
If you need to start completely fresh, then you'll want to erase your startup disk using Disk Utility. If you want the content on your Mac to stay intact, skip to the next section.
- Click on your startup disk in the Disk Utility sidebar.
- Click Erase.
- Click the Format drop-down menu.
- Click on the format you want to use for your drive. If you're running macOS High Sierra on a Mac with an SSD, your choices will be some form of APFS.
- Click Erase. Your drive will proceed to be erased.
How to reinstall macOS while in Recovery mode
The next step is to reinstall macOS.
- Click Reinstall macOS.
- Click Continue.
- Click Continue.
- Click Agree.
- Click Agree.
- Click on the drive on which you wish to install macOS.
- Enter your Apple ID and password if you're asked to, though you might not be.
- Click Install.
Your Mac will now go through the normal macOS installation process, eventually restarting. If you're starting from scratch, you'll need to set up your Mac from scratch.
Questions?
If you have any more questions about reinstalling macOS on your Mac, let us know in the comments.
macOS
Main
Rachel is trying to sell her Mac, but…
My friend was wiping my Mac so I could sell it and I’m pretty sure they’ve deleted the start up disk? It’s not letting me reinstall the OS on a recovery startup.
She wonders about a fix. There are a couple of options with an erased partition.
![Install recovery partition windows 10 Install recovery partition windows 10](https://www.johannesluderschmidt.de/wp-content/uploads/2015/02/parallelsInstallYosemite10_10FromRecoveryPartition.jpg)
Because Recovery didn’t work, the fastest way to install fresh is to make or borrow a macOS installer on a USB flash drive or a disk drive. We have instructions for making a bootable installer with macOS Sierra (as well as archived versions for several previous releases). You need at least an 8GB flash drive. The article includes instructions on obtaining the installer, which might involve you having to use someone’s else Mac to download it, if you don’t have a replacement Mac on hand yet.
But if you can’t get access to another Mac or the necessary drive, it’s still possible to use a different Recovery mode on all recent Macs, dating back to 2010. Normally, you can start up a Mac while holding down Command-R to boot into what Apple now calls macOS Recovery. That allows you to run Disk Utility, reinstall or wipe and install the system, access Terminal for command-line functions, and so on. In that mode, when you choose to reinstall without erasing the drive, my recollection is that Recovery looks for the current OS system installer on your startup disk in the Applications folder, and uses that. (Apple doesn’t document that, and I haven’t had to test that for years.)
Failing finding it, Recovery downloads the currently installed version of macOS (or OS X), which is about 5GB. When complete, it installs it and reboots, and places the installer in the Applications folder.
However, there’s yet another option: macOS Recovery over the Internet, which requires either a Mac model released in 2012 or later, or most 2010 and 2011 models with a firmware upgrade applied. There, the Mac reaches out over a Wi-Fi or ethernet connection to download the relatively modest Recovery software, which then bootstraps the download of the full macOS installer.
Apple says Internet-based Recovery should happen automatically on supported models, and you should see a spinning globe when that mode is invoked while the download occurs. However, if you have normal Recovery installed and it refuses to install macOS for some reason, you can manually invoke Internet Recovery.
While Command-R at startup always installs whatever the most recent version you installed on your Mac, holding down Command-Option-R brings down the very latest compatible version that can be installed. Apple also offers Shift-Command-Option-R, which installs the version of OS X or macOS with which your computer shipped, or the next oldest compatible system still available for download.
(Apple just changed this behavior with 10.12.4, but if you’re using Internet Recovery for a clean install on an erased drive, the new behavior should be active as it will be pulled from the version of Recovery that’s bootstrapped from Apple’s servers. The pre-10.12.4 option is simply Command-Option-R, but it acts like the new Shift-Command-Option-R, installing the shipped OS or the oldest compatible version.)
Apple recommends the Command-Option-R option as the only safe way to reinstall a Mac with El Capitan or earlier versions of macOS if you want to be sure your Apple ID doesn’t persist even after erasure.
Ask Mac 911
We’ve compiled a list of the questions we get asked most frequently along with answers and links to columns: read our super FAQ to see if your question is covered. If not, we’re always looking for new problems to solve! Email yours to [email protected] including screen captures as appropriate. Mac 911 can’t reply to—nor publish an answer to—every question, and we don’t provide direct troubleshooting advice.
Apple has made the installation process for OS X Lion (10.7) slightly different than it was for previous versions of the operating system. Even with the differences, you can still create a clean installation of Lion on an internal drive, a partition, an external drive, or a USB flash drive.
This step-by-step article looks at installing Lion on a drive or partition, either internally on your Mac or on an external drive. For those of you who want to create a bootable USB flash drive with Lion installed, check out the guide: Create an Emergency Mac OS Boot Device Using a USB Flash Drive.
What You Need to Install Lion
Purchase Lion from the Apple Store online. You receive a content code to the Mac App Store, usually within one day. After you download the installer, copy it to any Mac that meets the minimum hardware requirements and install Lion. The Lion installer is downloaded to your Applications folder, and it is just under 4 GB in size. The system requirements are:
- Intel Core 2 Duo, i3, i5, Core i7 or Xeon processor
- Mac OS X Snow Leopard v10.6.6 or later (v10.6.8 is recommended)
- 7 GB of free hard drive space
- 2 GB of RAM
You can install Lion on any internal drive, including SSDs (solid state drives). Also, you can install Lion on any external drive that is connected to your Mac by USB 2.x, USB 3, FireWire 400/800, or Thunderbolt. An eSATA-based external drive probably won't work as a bootable installation destination because most add-on eSATA controllers don't support booting OS X.
The Lion Recovery partition takes 650 MB of the free space. The Lion installer creates two partitions, one for Lion and one for recovery tools. You can use the Recovery Partition to repair drives, fix permissions, and format drives, as well as reinstall Lion if needed. The Recovery Partition includes a bootable system with Disk Utility.
Clean Install Preparation
To perform a clean install of Lion, you must have a disk or partition available that uses the GUID Partition Table and is formatted with the Mac OS X Extended (Journaled) file system. The target volume should be erased at best; at a minimum, it should not contain any OS X system.
With previous versions of OS X installers, you could erase the target drive as part of the installation process. With the Lion installer, there are two methods of performing a clean install. One method requires you to create a bootable Lion install DVD, and the second lets you perform a clean install using the Lion installer you downloaded from the Mac App Store.
The difference between the two methods is that to use the Lion installer directly, you must have a drive or partition that you can erase before running the installer. Using a bootable Lion install DVD allows you to erase a drive or partition as part of the installation process.
If you want to use your current startup drive as the target for a clean install, you need to the use the bootable Lion install DVD method as outlined in Lion Install - Use a Bootable Lion DVD to Perform a Clean Install.
If you're going to perform a clean install of Lion on a drive other than your current startup drive, then you're ready to proceed.
Perform a Backup
Before you begin the Lion installation process, back up your existing OS X system and user data. Performing a clean install on a separate drive or partition shouldn't cause any data loss with your current system, but stranger things have happened, and it is best to be prepared.
At a minimum, make sure you have a current backup. For more protection, make a bootable clone of your current startup drive. You can find the method here: Back Up Your Mac: Time Machine and SuperDuper Make for Easy Backups.
If you would rather use Carbon Copy Cloner, you will find the developer makes older versions of the app available that work with OS X Snow Leopard and Lion.
Format the Destination Drive
You must erase the target drive before you can start the Lion installation process. Remember that to use the Lion installer as downloaded from the Mac App Store, you must have a working copy of OS X to start the installer from. You may need to create a new partition to install to or resize existing partitions to create the necessary space.
If you need instructions for adding, formatting, or resizing a drive's partitions, you can find them here: Disk Utility - Add, Delete, and Resize Existing Volumes With Disk Utility
Use the OS X Lion Installer
Before you start the Lion installer, close all other applications that are currently running on your Mac.
![Install Os X Recovery Partition Install Os X Recovery Partition](https://www.macobserver.com/wp-content/uploads/2017/04/Running_Recovery_Partition_Creator_9.jpeg?x98952)
The Lion installer is located in the Applications folder, and the file is named Install Mac OS X Lion. The download process from the Mac App Store also created an Install Mac OS X Lion icon in your Dock.
- Start the Lion installation process by clicking the Lion installer Dock icon, or double-clicking the Install Mac OS X Lion application in the Applications folder.
- Click Continue in the window that opens.
- Scroll through the terms of use and click Agree.
- The Lion installer assumes you want to install Lion on the current startup drive. To select a different target drive, click Show All Disks and select the target disk from the list (the disk you erased earlier).
- With the target disk highlighted, click Install.
- Enter your admin username and password to begin the installation process and click OK.
- Wait while the Lion installer copies the necessary files to the target disk. When the copying is finished, you are prompted to restart your Mac. Click Restart.
After your Mac restarts, the installation process continues. A progress bar displays along with an estimate of the time it will take to complete the installation. Installation speed ranges from 10 to 30 minutes.
Note: If you have multiple displays connected to your Mac, turn all of them on before you begin the Lion installation process. The installer may display the progress bar on a display other than your usual main screen; if that display isn't on, you'll wonder what's happening.
OS X Lion Setup Assistant
When the installation of OS X Lion is complete, your Mac displays a Welcome window, which marks the start of the registration and setup process for Lion.
- In the Welcome window, select the country or region where you use your Mac and click Continue.
- A list of keyboard styles displays. Select the type that matches yours and click Continue.
Migration Assistant
Reinstall Mac Os X Recovery Partition
Because this is a clean install of OS X Lion, you can use the Migration Assistant to transfer data from another Mac, PC, Time Machine, or another disk or partition on your Mac.
However, it is better not to use the Migration Assistant at this point, opting instead for a clean installation of Lion. After you know Lion is installed and working correctly, run the Migration Assistant from the Lion installation to move any user data you need to the Lion disk. You can find the Migration Assistant in the Utilities folder inside the Applications folder.
Registration
Registration is optional. You can click through the next two screens if you want. If you do fill in the registration information, some of the applications you use in Lion are pre-populated with appropriate data. Specifically, Mail and Address Book will already have your primary email account information partially set up, and Address Book will have your personal entry already created.
Enter your Apple account information, and click Continue to open a window that requests information. You aren't required to enter it. When you're finished, or if you prefer not to register, click Continue.
Administrator Account
Lion requires at least one administrator account to be set up. You can use the administrator account to perform most Lion housekeeping tasks, to create additional users, and to install any applications that require administrator privileges.
- When prompted for the administrator account name, enter your name.
- Enter your shortname, which is a shortcut name used for the administrator account and the name of the account's home directory. Shortnames cannot be changed, so be sure you're happy with the name you enter. You'll be living with it for a long time.
- Enter the password you want to use, along with any additional information requested and then click Continue.
- You can associate an image or picture with the account you're creating. If you have a webcam connected to your Mac, you can snap a picture of yourself to use. You can also choose one of many pictures already installed in Lion. Make your selection, and click Continue.
Learning to Scroll
The Lion Setup Assistant is just about done. The final step shows you how to use the new touch-based gesture system in Lion. Depending on the type of touch-based input device you have (Magic Mouse, Magic Trackpad, or integrated trackpad), you see a description of how to scroll. Follow the instructions to scroll down through the text area, and click the Start Using Mac OS X Lion button.
Boot Into Os X Recovery Partition
Just One More Thing
Install Os X From Recovery Partition
That's it. You can start exploring Lion, but before you head off, use the Software Update service to ensure that you have all the latest patches, device drivers, and other undercover goodies your Mac may need to perform at its best. From the Apple menu, select Software Update, and then follow the onscreen instructions.