How to Install MacOS into USB Drive ?

Installing any old or new macOS onto a USB drive connected to a MacBook allows you to create a portable macOS installation that can boot and run directly from the USB.

This is different from creating a bootable installer USB (which only installs macOS onto another drive); here, the USB itself becomes a fully functional macOS system.

Below are the detailed steps to achieve this using built-in macOS tools and an official installer.

---

Prerequisites

• MacBook: Any Mac capable of running the desired macOS version.
• USB Drive: At least 32GB (64GB+ recommended for better performance and storage). A fast USB 3.0/3.1 drive improves speed.
• macOS Installer: The full installer app for your chosen macOS version (e.g., Install macOS Monterey.app, Install macOS High Sierra.app) in /Applications.
• Internet Connection: Required during installation for some macOS versions.
• Time: 30-60 minutes, depending on USB speed and macOS version.

---

Step-by-Step Instructions to create macOS USB installer

1. Obtain the macOS Installer

• New macOS (e.g., Ventura, Monterey):
  • On a compatible Mac, download from the Mac App Store: Search for the OS (e.g., “Monterey”), click “Get,” and find it in /Applications.
  • On an unsupported Mac, use gibMacOS:
    git clone https://github.com/corpnewt/gibMacOS.git cd gibMacOS python3 gibMacOS.command
  • Select your macOS version, download the .pkg, and extract Install macOS [Version].app to /Applications.
• Old macOS (e.g., High Sierra, El Capitan):
  • Use Apple’s support pages (e.g., “How to download macOS”) or gibMacOS to get older installers.
• Verify the app is in /Applications:
  ls /Applications/ | grep "Install macOS"

2. Prepare the USB Drive

• Connect the USB Drive:
  • Plug it into your MacBook.
• Open Disk Utility:
  • Go to Applications > Utilities > Disk Utility.
• Erase the USB Drive:
  • Select the USB drive in the left sidebar (top-level device, e.g., “32.0 GB SanDisk”).
  • Click Erase and configure:
  • Name: MacOSUSB (or any name).
  • Format: APFS (for macOS High Sierra and later) or Mac OS Extended (Journaled) (for Sierra and earlier).
  • Scheme: GUID Partition Map.
  • Click Erase. This formats the drive for macOS.
• Check Mount Point:
  • After erasing, it mounts as /Volumes/MacOSUSB (or your chosen name). Confirm:
    ls /Volumes/

3. Install macOS onto the USB Drive

• Start the Installer:
  • Open the installer app from /Applications (e.g., double-click Install macOS Monterey.app in Finder).
  • Click Continue on the welcome screen.
• Select the USB Drive as the Destination:
  • When prompted to “Select a disk to install macOS,” click Show All Disks.
  • Choose your USB drive (e.g., MacOSUSB) from the list.
  • Click Install or Continue.
• Enter Admin Password:
  • Provide your admin credentials if prompted.
• Wait for Installation:
  • The MacBook will copy the macOS system files to the USB and restart (this may happen multiple times).
  • Installation takes 20-40 minutes, depending on the USB speed and macOS version. The USB will become a bootable macOS volume.

4. Configure the USB macOS (First Boot)

• Boot from the USB:
  • After installation, restart your MacBook while holding the Option (⌥) key.
  • In the boot menu, select the USB drive (e.g., “MacOSUSB” or “macOS Monterey”).
• Complete Setup:
  • Follow the on-screen prompts (language, Apple ID, etc.) to set up the macOS instance on the USB.
  • Once finished, you’ll have a fully functional macOS running from the USB.

5. Verify and Test

• Check the System:
  • Go to Apple menu > About This Mac to confirm the correct macOS version is running.
• Eject Properly:
  • When done, shut down the MacBook (Apple menu > Shut Down), then remove the USB.
  • To use it again, reboot with Option and select the USB.

---

Alternative: Use createinstallmedia + Manual Install

If the direct installer method fails (e.g., for older macOS versions), create a bootable installer first, then install to the USB:

1- Make a Bootable Installer:

   sudo /Applications/Install\ macOS\ [Version].app/Contents/Resources/createinstallmedia --volume /Volumes/TempUSB --nointeraction

• Use a temporary USB (TempUSB) for this step.

2- Boot from Installer:

• Restart, hold Option, select the installer USB.

3- Install to Target USB:

• In the installer, open Disk Utility, erase your target USB as APFS or Mac OS Extended.
• Select the target USB as the install destination and proceed.

---

Troubleshooting

• “Installer not found”:
• Ensure the .app is in /Applications and named correctly (e.g., no trailing spaces).
• USB Not Bootable:
• Verify the format (APFS or Mac OS Extended) and scheme (GUID) in Disk Utility.
• Slow Performance:
• Use a USB 3.0/3.1 drive and port. SSD-based USBs are ideal for better speed.
• Unsupported Mac:
• For old Macs running new macOS (e.g., Monterey on a 2011 MacBook), use OpenCore Legacy Patcher (OCLP) post-install to patch the USB system.

---

Notes

• Performance: Running macOS from a USB is slower than an internal drive—expect some lag, especially with older USB 2.0 drives.
• Portability: This USB can boot any compatible Mac (or patched unsupported Mac) by holding Option at startup.
• Space: Install only the base system initially; add apps/data later to avoid filling the drive.