How to create a bootable macOS Sequoia USB installer?

Creating a bootable macOS Sequoia USB installer is a straightforward process that allows you to install or repair macOS Sequoia (version 15.x) on a compatible Mac, or use it for troubleshooting or clean installations.

This guide uses built-in macOS tools, specifically the createinstallmedia command, to transform a USB drive into a bootable installer.

Below are detailed step-by-step instructions tailored for macOS: –

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Prerequisites

• macOS Sequoia Installer: The full Install macOS Sequoia.app (~12-14GB) located in /Applications. See Step 1 for how to obtain it if missing.
• USB Drive: Minimum 16GB capacity (32GB recommended for reliability). A USB 3.0/3.1 drive speeds up the process.
• Mac with Admin Access: A Mac running macOS 10.13+ (High Sierra or later) with an admin account.
• Free Space: ~20GB on the Mac for temporary files.
• Time: ~20-30 minutes, depending on USB speed.

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Step-by-Step Instructions

Step 1: Obtain the macOS Sequoia Installer

• Check for Installer:
• Open Finder, navigate to /Applications, and look for Install macOS Sequoia.app.
• Verify its size (should be ~12-14GB):
  du -sh /Applications/Install\ macOS\ Sequoia.app
• Download if Missing:
• Mac App Store (Supported Macs):
  • On a compatible Mac (e.g., 2018 MacBook Air or later), open the App Store.
  • Search for “Sequoia” (availability depends on your host macOS—may redirect to Software Update).
  • Click “Get” to download to /Applications.
• Software Update Command (Alternative):
  • In Terminal:
    softwareupdate --fetch-full-installer --full-installer-version 15.0
  • Downloads Install macOS Sequoia.app to /Applications.
• gibMacOS (Unsupported Macs or Older Hosts):
  • Open Terminal:
    /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)" brew install python git clone https://github.com/corpnewt/gibMacOS.git cd gibMacOS python3 gibMacOS.command
  • Select “macOS Sequoia” (15.x), download the .pkg, and extract:
    pkgutil --expand-full "macOS Downloads/publicrelease/InstallAssistant.pkg" ~/Desktop/SequoiaInstaller mv ~/Desktop/SequoiaInstaller/Applications/Install\ macOS\ Sequoia.app /Applications/
• Move if Needed:
• If downloaded elsewhere:
  mv ~/Downloads/Install\ macOS\ Sequoia.app /Applications/

Step 2: Prepare the USB Drive

• Insert USB Drive:
• Plug it into your Mac. It should appear in Finder or on the Desktop.
• Open Disk Utility:
• Go to Applications > Utilities > Disk Utility, or use Spotlight (Command + Space, type “Disk Utility”).
• Erase the USB Drive:
• In Disk Utility, select the USB drive in the left sidebar (top-level device, e.g., “16.0 GB SanDisk”, not a partition).
• Click Erase and configure:
  • Name: SequoiaUSB (or any name).
  • Format: Mac OS Extended (Journaled) (required for the bootable installer).
  • Scheme: GUID Partition Map.
• Click Erase. Warning: This wipes all data—back up anything important.
• Verify Mount Point:
• After erasing, it mounts as /Volumes/SequoiaUSB. Confirm:
  ls /Volumes/

Step 3: Create the Bootable Installer

• Run createinstallmedia:
• Open Terminal (Applications > Utilities > Terminal).
• Enter this command, replacing SequoiaUSB with your USB’s volume name if different:
  sudo /Applications/Install\ macOS\ Sequoia.app/Contents/Resources/createinstallmedia --volume /Volumes/SequoiaUSB --nointeraction
• Breakdown:
  • sudo: Admin privileges.
  • --volume: Specifies the USB.
  • --nointeraction: Runs without prompts.
• Enter your admin password (it won’t display) and press Enter.
• Process:
• Takes 10-20 minutes. Terminal shows progress (e.g., “Erasing disk…”, “Copying installer files…”).
• Ends with:
  Install media now available at "/Volumes/Install macOS Sequoia"

Step 4: Verify the Bootable USB

• Check Result:
• The USB is renamed to Install macOS Sequoia and mounted at /Volumes/Install macOS Sequoia.
• In Finder, it appears with a Sequoia installer icon.
• Inspect Contents:
• Run:
  ls /Volumes/Install\ macOS\ Sequoia/
• Should list files like InstallESD.dmg and boot components.

Step 5: Eject the USB

• Safely Remove:
• In Finder, click the eject icon (⏏) next to Install macOS Sequoia.
• Or in Terminal:
  diskutil eject /Volumes/Install\ macOS\ Sequoia
• Unplug the USB once ejected.

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Using the Bootable USB

• Install Sequoia:
• Insert USB into the target Mac.
• Restart, hold Option (⌥) until the boot menu appears.
• Select Install macOS Sequoia > Follow prompts to install.
• Troubleshooting/Recovery:
• Boot to the USB to access Disk Utility, Terminal, or reinstall options.
• Unsupported Macs: For pre-2018 Macs, use OpenCore Legacy Patcher (OCLP) post-install to enable Sequoia.

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