Creating a bootable official macOS Big Sur USB install drive is a reliable way to install or repair macOS Big Sur (version 11.x) on a compatible Mac using built-in macOS tools.
This process uses the Install macOS Big Sur.app and the createinstallmedia command to transform a USB drive into a bootable installer.
Below are the detailed, step-by-step instructions to create a bootable macOS Big Sur usb installer
A video describes the process to create a bootable macOS Big Sur USB installer
Prerequisites
macOS Big Sur Installer: The full Install macOS Big Sur.app (approximately 12-13GB), located in /Applications. See the note at the end if you need to download it.
USB Drive: Minimum 16GB capacity (32GB recommended for reliability). A USB 3.0 drive is faster but not required.
Mac with Admin Access: You’ll need a Mac to run the commands and an admin password.
Time: About 20-30 minutes, depending on USB speed.
Step-by-Step Instructions to create a bootable macOS Big Sur USB installer
1. Obtain the macOS Big Sur Installer
Check /Applications:
Open Finder and look for Install macOS Big Sur.app in /Applications.
Verify its size (should be ~12GB): du -sh /Applications/Install\ macOS\ Big\ Sur.app
If Missing:
On a compatible Mac (e.g., 2013 MacBook Pro or later), download it from the Mac App Store:
Open the App Store, search “Big Sur,” click “Get,” and let it download to /Applications.
On an unsupported Mac or if unavailable, use gibMacOS: git clone https://github.com/corpnewt/gibMacOS.git cd gibMacOS python3 gibMacOS.command
Select “macOS Big Sur” (11.x), download the .pkg, and extract Install macOS Big Sur.app to /Applications.
2. Prepare the USB Drive
Insert the USB Drive:
Plug the USB into your Mac. It will 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 from the left sidebar (top-level device, e.g., “16.0 GB SanDisk,” not a partition).
Click Erase and set:
Name:BigSurUSB (or any name you prefer).
Format:Mac OS Extended (Journaled) (required for Big Sur’s bootable installer).
Scheme:GUID Partition Map.
Click Erase. This wipes the drive—back up any data first.
Verify Mount Point:
After erasing, it mounts as /Volumes/BigSurUSB. Confirm: ls /Volumes/
3. Create the Bootable Installer
Run the createinstallmedia Command:
Open Terminal (Applications > Utilities > Terminal).
Enter this command, replacing BigSurUSB with your USB’s volume name if different: sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/BigSurUSB --nointeraction
Breakdown:
sudo: Runs with admin privileges.
--volume: Targets the USB drive.
--nointeraction: Automates without prompts.
Enter Admin Password:
Type your password (it won’t display) and press Enter.
Wait for Completion:
The process erases the USB, copies the installer files, and makes it bootable. It takes 10-20 minutes.
Terminal will show progress (e.g., “Copying to disk…”), ending with: Install media now available at "/Volumes/Install macOS Big Sur"
4. Verify the Bootable USB
Check the Result:
The USB will be renamed to Install macOS Big Sur and mounted at /Volumes/Install macOS Big Sur.
In Finder, it should appear with a Big Sur installer icon.
Inspect Contents:
Run: ls /Volumes/Install\ macOS\ Big\ Sur/
You’ll see files like InstallESD.dmg and boot components.
5. Eject the USB
Safely Remove:
In Finder, click the eject icon next to Install macOS Big Sur.
Or in Terminal: diskutil eject /Volumes/Install\ macOS\ Big\ Sur
Unplug the USB once ejected.
Using the Bootable USB
Install Big Sur:
Insert the USB into the target Mac.
Restart while holding Option (⌥) until the boot menu appears.
Select Install macOS Big Sur and follow the prompts to install on the internal drive.
Unsupported Macs: For pre-2013 Macs, use OpenCore Legacy Patcher (OCLP) to patch the installer post-creation for compatibility.
Troubleshooting
“Command not found” or “Permission denied”:
Verify the installer path (/Applications/Install\ macOS\ Big\ Sur.app). If renamed (e.g., with “Beta”), adjust the command.
Ensure sudo is used correctly.
“Volume not found”:
Check the USB’s mount point: ls /Volumes/
Update the command with the exact name (e.g., /Volumes/MyUSB).
Process Hangs:
Use a USB 3.0 port/drive if available. Cancel with Control + C and retry if needed.
Notes
Space: The USB must be empty and properly formatted—16GB is the minimum, but 32GB avoids potential issues.
Speed: USB 3.0 cuts creation time significantly (e.g., 5-10 minutes vs. 20+ on USB 2.0).
Reusability: This USB can install Big Sur on multiple Macs or be reformatted later.
You now have a bootable macOS Big Sur USB installer.
