/ How to

How To Clean Install macOS from a USB Installer Drive

Introduction

A clean install of macOS involves erasing your Mac’s disk and installing a fresh copy of the operating system. This can help resolve system issues, free up disk space, and improve performance. It’s also recommended before selling or gifting your Mac.

There are a few ways to clean install macOS, but using a bootable USB installer drive is often the easiest method. Here is a step-by-step guide on how to clean install macOS from a USB drive.

Prerequisites

Before starting, make sure you have the following:

  • A USB flash drive with at least 16GB of storage
  • A Mac running macOS 10.13 High Sierra or later
  • The macOS installer for the version you want to install downloaded from the App Store
  • Backups of your important files (using Time Machine or another backup service)

Step 1: Create the Bootable USB Installer

The first step is to create a bootable USB installer drive from the macOS installer you downloaded.

To do this:

  • Connect your USB drive to your Mac
  • Launch Terminal (in Applications > Utilities)
  • Type in the command to create the bootable installer, replacing “MyVolumeName” with your actual USB drive name:
sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolumeName
  • Enter your admin password when prompted
  • Wait for the process to finish. This can take a while depending on your USB speed.

Once done, the USB drive will contain the files necessary to install macOS.

Step 2: Startup from the USB Installer

Next, you’ll need to boot your Mac from the installer USB drive instead of your normal startup disk.

To do this:

  • Connect the bootable installer USB drive
  • Turn on your Mac and immediately press and hold the Option (⌥) key after you hear the startup chime
  • Select the orange USB icon labeled “Install macOS Monterey”
  • Click the arrow button below it to boot from the installer

Step 3: Erase Your Current Disk

With your Mac started from the installer, you now need to erase your current startup disk to prepare it for a clean install.

  • Open Disk Utility from the Utilities menu
  • Click “View” > “Show All Devices”
  • Select your Mac’s disk (not a volume or partition)
  • Click Erase near the top
  • Choose a name for your disk
  • Select APFS or Mac OS Extended (Journaled) format
  • Click Erase

This will delete all data on the disk and reformat it ready for the clean install.

Step 4: Install macOS

With your drive erased, close Disk Utility then proceed to install macOS:

  • Click Continue in the macOS installer window
  • Click Agree to the software license terms
  • Select your newly erased disk as the destination
  • Click Install and wait for the process to complete

Your Mac will restart a few times. The whole process can take over an hour depending on your Mac model.

Step 5: Complete Setup

Once installation finishes, you’ll be greeted with the macOS setup assistant. Follow the onscreen prompts to complete setup, including:

  • Selecting your country/region
  • Configuring privacy settings
  • Creating a user account
  • Setting up iCloud, Touch ID, Apple Pay etc. if desired

And that’s it! Your Mac now has a fresh copy of macOS installed. From here, you can manually move your files from your backups or migrate data using Migration Assistant.

Summary

Clean installing the latest macOS version from a USB drive is straightforward with these steps:

  1. Create a bootable USB installer
  2. Boot from the installer drive
  3. Erase your startup disk
  4. Install the macOS files
  5. Complete first-time setup

Doing this provides a blank slate to resolve issues or prepare your Mac for sale or gift. Just be sure to fully back up your data first!

Related Posts