However, if we have to give away the Mac or want to restore it after many updates, we can follow the procedure for manually create an installation flash drive. In the guide that follows we will therefore see how to download the latest version of the macOS operating system, how to create the USB key and how to install it from scratch sul nostro Mac, Mac Pro, iMac, MacBook o Mac Mini.
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To perform a new installation of macOS we need one USB stick at least 16 GB. It is also possible to use a USB external hard drive connected to your Mac, but it is advisable to always use a USB stick as it is faster and more practical to use than any mechanical hard drive.
The key will be inserted into the Mac at the appropriate time, so as to transform it into a key to start and install macOS.
How to download the operating system
Currently the latest version of macOS is Monterey and we can download it directly from our Mac or MacBook by opening the App Store, looking in the search bar “Monterey”by pressing on View on the operating system entry and then pressing on Get.
The installation file is around 12GB, so it may take some time to finish loading.
How to prepare the USB stick
After downloading the system let’s format the USB stick opening the application Utility Disco on the Mac, by selecting the drive in the sidebar, pressing on the tab Cancelformatting the drive as “Mac OS Extended (Journaled)” and leaving the disk name “untitled”.
Let’s now press on Cancel and, after formatting the USB stick, close Disk Utility and create the installation USB stick with Install Disk Creator.
This is by far the easiest way to create a bootable drive to install macOS from scratch, the only caveat is that the installation file is inside the folder Applications.
To use this program let’s start it, make sure that the installer of the macOS version we are formatting is present (at this moment Monterey), then press down on Create Installer.
At the end of the creation we restart the Mac with the USB drive connected and hold down the key Option (the one that on Windows is the Alt key) to access the screen that allows you to select the starting disk, from where we can choose the USB drive just created.
On Macs with Apple M1 processors, the recovery screen can be called up by holding down the power button for a few seconds.
Create USB stick with DiskMaker X
Another very useful program to install macOS from a USB stick from scratch is DiskMaker X.
The steps to follow are practically the same as for the procedure seen above; download the installer of the macOS system in use, connect the USB key, format it and, as soon as it is ready, install DiskMaker X starting the DMG file and dragging the program icon into the folder Applications (how almost all apps install on Mac).
Once installed we will have to assign it the right permissions on Mac, so that the procedure does not fail during creation. Immediately after installation we press on the top left on the Apple symbol, then on System Preferences, let’s take it in Security and Privacy -> Privacy and press on the item Accessibility.
Press the padlock at the bottom left and unlock the permissions by entering the access password. Now let’s add the program DiskMaker X to the list, by pressing the + symbol and looking for it in the Applications folder of the Finder.
As soon as the app is added to the exceptions, let’s start it from the Launchpad, choose the latest version of macOS and press on the item Erase then create the disk.
As soon as the USB key is ready, restart the Mac and access the key by holding down the key Options (Alt) or by holding down the power key (on Apple chip computers).
Create a USB key from the terminal
For experts, it is also possible to launch commands from the Mac terminal to create USB sticks on the fly to restore various versions of the Mac, without having to download third-party programs. To proceed we open the Launchpadlet’s open the app Terminal and launch the right command based on the macOS version downloaded from the App Store.
/Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia
/Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia
/Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia
After launching the command, we follow the procedure indicated to create the USB key with the version of macOS we need.
Restore macOS from USB
Whatever method you choose to create the USB stick, we can install macOS from scratch by booting Utility Discoselecting the Mac disk from the left sidebar and clicking on the item Initialize.
Now we indicate the name to be assigned to the drive after formatting, we verify that in Format and Scheme items are selected OS X extended (journaled) e Partition Map (GUID) and start formatting by pressing on Initialize.
At the end of the formatting the Mac will restart and we can start over as if it had just left the factory.
Even if the Mac hardly needs a complete formatting, it is better to keep this in mind for when we want to format the Mac to give it to another person and we do not want them to be able to see our personal files or access our browsers.
To create the macOS key from Windows, we invite you to read our guide on how create the USB key to install MacOS from Windows.
If, on the other hand, we want to restore Mac without a USB stick, we can read our in-depth analysis on how to reset / reset your Mac and reinstall MacOS.