How To Mac

How to Clean Install macOS with InstallAssistant

Written by John

The 18th major release of macOS, macOS Monterey is the successor to macOS Big Sur. Apple announced the new operating system at WWDC 2021. The public release of macOS 12 Monterey was on October 25, 2021.

The latest macOS Monterey is better than Big Sur and has lots of interesting features. However, some of the advanced features in macOS Monterey have hardware requirements that only newer Macs are able to use them.

If as a Mac user, you run into system issues, you need to be able to safely clean install the latest operating system and continue your work. When you clean install macOS Monterey, you get a fresh start that can solve a lot of the issues related to user experience, connectivity, and security.

The reason why you want to clean install macOS Monterey can differ. You may want to sell it, clean up partitions, or troubleshoot issues. Reinstalling a Mac isn’t easy. Especially with the new the installation process with a bootable USB, you may encounter the “Installation cannot proceed because the installer is damaged” error. There are many reasons why you may encounter such an error. In this guide, we will guide you through the installation process so that you can avoid all the installation errors.

An install assistant is a software that manages the installation of macOS in Recovery Mode. It will allow you to clean install macOS Monterey without any errors. The installation process becomes so much easier when you do it with an install assistant.

How to Clean Install macOS with Install Assistant

To clean install the latest macOS Monterey, you can use installassistant. The process is smoother and all you have to do is follow a few steps to complete the process.

1. Download macOS Installer

You have to download the macOS Monterey installer for the installation process. If you’re running macOS Monterey, follow the steps below to download the installation package:

Step 1: Click on the Apple icon on the home screen and select System Preferences
Step 2: Select Software Update
Step 3: Download macOS Monterey installation files

In case you’re running a macOS older than macOS Monterey, you need to download
macOS Monterey installer from the Mac App Store. You can also search for ‘macOS Monterey’ on the Mac App Store to download the installer.

The macOS Monterey installer is 12.6 GB in size and hence can take time for the download to complete. When the download is complete, the macOS installer will launch automatically. However, we don’t need the installation process to start just yet and hence choose to not continue further.

2. Move macOS Installer to the Temporary Disk or Flash Drive

We will move the macOS Monterey file to a temporary disk or USB drive that we will be using for the clean installation. If you don't have a USB Drive, you can create a Temporary Disk.

Follow the steps below to create a Temporary Disk:
Step 1: Go to Applications > Utilities, Open Disk Utility, Click on "View > Show All Devices"

Add new Temporary Disk

Step 2: Click on your Disk and select Partition, Click on "+" button to add new partition.
Name: Temporary Disk
Format: APFS
Size: 30 GB

Create a New Partition

Disk Utility will create the partition. This process can take some time. When it is completed, click on Done.

All you need is a copy of the macOS Monterey installer to Temporary Disk.

Copy Install macOS Monterey App to Temporary Disk

3. Go to Recovery Mode

Intel Mac users need to press and hold the Command + R key combination during system startup to enter Recovery Mode. Alternatively, M1 Mac users need to hold down their Power button when they boot their computer to get into Recovery Mode.

Open Disk Utility in Recovery Mode

In the Recovery Mode screen, click on Disk Utility and erase the container disks by choosing them and clicking on the Erase option. Format the hard disk to APFS partition.

Clean your Container Disk

4. Use Terminal to Open InstallAssistant

To clean install macOS Monterey after you’ve erased the internal storage, you need to use Terminal. In Recovery mode, select "Utilities > Terminal"

Open Terminal in Recovery Mode

Paste the following codes into Terminal to install macOS Monterey:
/Volumes/Temporary\ Disk/Install\ macOS\ Monterey.app/Contents/MacOS/InstallAssistant
Clean Install macOS Monterey with InstallAssistant

Follow the on-screen instructions to complete the clean install of macOS Monterey.

Install macOS Monterey

5. Delete Temporary Disk in macOS Monterey

Open Disk Utility in Applications > Utilities. Click on Temporary Disk  partition and select "-" to delete it.

Delete Temporary Disk in macOS Monterey

That’s it. You now have a clean installation of macOS Monterey on your Mac.

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