Mac OS Sequoia installer drive setup issues.

Make sure you have not happened to download a tiny "stub" installer but a proper about 12 GB or so installer.

You might have to grant the Terminal enough access rights via Settings > Security & Privacy > Files and Folders > All On (seems to be enough), or > Full Disk Access then click on the + and locate Terminal.

Format the USB drive as Mac OS Extended (GUID) on the same computer you prepare the installer (drive formatted on an Intel Mac might not boot Silicon Mac). APFS does not work.

USB drive might be needed to be plugged into the computer directly, not an USB hub (otherwise there might be a final generating "boot files" error).

Steps to Create a Bootable macOS Sequoia USB

1. 1. Download the macOS Sequoia Installer:
2. Open the Mac App Store and download the "Install macOS Sequoia" application. Make sure to download it directly from the app store and not through System Settings to get the full installer. 
3. 2. Quit the Installer:
4. Once the installer application launches, quit it by going to Install macOS Sequoia > Quit Install macOS Sequoia. 
5. 3. Connect and Prepare the USB Drive:

• • Plug in a USB flash drive with at least 32 GB of storage. 
  • Back up any important data from the USB, as it will be completely erased. 

1. 4. Open Terminal:
2. Navigate to Applications > Utilities and open the Terminal application. 
3. 5. Execute the Creation Command:
4. In the Terminal window, enter the following command, replacing MyVolume with the actual name of your USB drive (if it doesn't have a space in the name): 

Code

    sudo /Applications/Install\\ macOS\\ Sequoia.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

• Note: If your USB drive's name has spaces, you'll need to drag the createinstallmediaexecutable from its location into the Terminal window to automatically insert the correct path and volume. 

1. 1. Enter Your Password and Confirm:
2. Press Enter, then type your administrator account password and press Enter again. When prompted, type Y and press Enter to confirm that you want to erase the USB volume. 
3. 2. Wait for Completion:
4. The creation process can take some time. Terminal will show the progress of erasing and copying the files. 
5. 3. Boot from the USB Drive:

• • Apple Silicon Macs: Shut down your Mac, then press and hold the power button to turn it on. Keep holding the power button until you see a list of startup options and select the USB drive. 
  • Intel-based Macs: Shut down your Mac, then press the power button and immediately hold down the Option (Alt) key until you see a list of bootable drives. Select the USB drive to begin the installation. 

CRESKI wrote:

Since the most current release of the Mac OS package, anytime I'm trying to create an installer drive I'm encountering an error I can't seem to resolve.

Installer media is Sequoia 15.6.1

sudo /Applications/Install\ macOS\ Sequoia.app/Contents/Resources/createinstallmedia --volume /Volumes/Sequoia

2025-09-01 09:04:38.802 createinstallmedia[2818:169127] The application with bundle ID com.apple.InstallAssistant.createinstallmedia is running setugid(), which is not allowed. Exiting.

Would appreciate any thoughts or insight on how to resolve this.

to be clear the flash drive will be erased and formatted

if you copy and paste:

sudo /Applications/Install\ macOS\ Sequoia.app/Contents/Resources/createinstallmedia --volume

note the trailing blank space; now drag and drop the USB directly onto the Terminal window to complete the path.

this command implies the download full installer (~15.3 GB) is sitting in the Applications folder.

The installer will automatically rename the USBinstaller

Maybe the Sequoia 15.6.1 installer is broken? Does it work if you via Terminal download some earlier version like 15.6? Does resetting PRAM help any (if you have Intel Mac)?

softwareupdate --list-full-installers

softwareupdate --fetch-full-installer --full-installer-version 15.6

CRESKI wrote:

Thanks for the steps here. I’ve actually tried exactly these steps. I actually think the package installer from Apple is bugged at the moment.

My Sonoma installer drive perfectly fine using the exact same steps. Sequoia is not

Perhaps I am parsing words

Package Installer, from where exactly

The Full Version of Sequoia 15.6.1 comes as a Self Contained Application installer

There are ways to download a Package Installer of Sequoia

Though, the Terminal commands to make a Bootable Installer are predicated on having the self contained " Install Sequoia App "

Did you include the Terminal.app in the Privacy & Security>Full Disk Access...(?)

Have you tried SW Updating Sonoma. To Sequoia?