MacOS Big Sur 11.6 will not create a bootable installer

Phillybass wrote:

I am attempting to create a bootable installer on a USB flash disk for MacOS Big Sur 11.6. This is something I have been able to accomplish with all previous versions of MacOS, and even with Big Sur when it was first released.

The error that I receive from the createinstallmedia app within the Big Sur installer is:

/Applications/Install macOS Big Sur.app does not appear to be a valid OS installer application.

Here are the details:

I downloaded the latest Big Sur 11.6 installer from the Apple App Store.

The USB flash disk is 32 GBytes, using GPT (GUID partition table), MacOS Extended (Journaled) formatting, and is named "MyVolumes"

I follow the instructions from Apple on how to create a bootable installer https://support.apple.com/en-us/HT201372

The command I use is:

$ sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

The error is always:

/Applications/Install macOS Big Sur.app does not appear to be a valid OS installer application.

Any ideas as to what may be the issue?

And how should I go about downloading the full size image, not this smaller installer program?

Can you verify this is the the correct: "/Volumes/MyVolume"

You can always drag & drop the USB to the Terminal window to complete the path if in doubt, copy and paste:

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

(note the trailing blank space when you copy & paste)

this command line above expects the Installer to be in the default location, ie Applications.

You can also try downloading directly from Terminal, copy and paste:

softwareupdate --fetch-full-installer --full-installer-version 11.6

delete and empty the trash any old installler

Phillybass wrote:

I am attempting to create a bootable installer on a USB flash disk for MacOS Big Sur 11.6. This is something I have been able to accomplish with all previous versions of MacOS, and even with Big Sur when it was first released.

The error that I receive from the createinstallmedia app within the Big Sur installer is:

/Applications/Install macOS Big Sur.app does not appear to be a valid OS installer application.

Here are the details:

I downloaded the latest Big Sur 11.6 installer from the Apple App Store.

The USB flash disk is 32 GBytes, using GPT (GUID partition table), MacOS Extended (Journaled) formatting, and is named "MyVolumes"

I follow the instructions from Apple on how to create a bootable installer https://support.apple.com/en-us/HT201372

The command I use is:

$ sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume

The error is always:

/Applications/Install macOS Big Sur.app does not appear to be a valid OS installer application.

The application is installed in the usual location:

$ /bin/ls -al /Applications/Install\ macOS\ Big\ Sur.app/

drwxr-xr-x 3 root wheel 96 Oct 4 09:35 Install macOS Big Sur.app

The size of the application is 37,479,165 bytes (20.6 MB on disk). This is odd, because it took almost 30 minutes to download - I think for that amount of download time it should have been three orders of magnitude larger. The last time I downloaded the installer, back in December of 2020, the size was 12 GBytes - and I was able to create a bootable installer.

If I run the installer without specifying a target volume, it works enough to tell me the proper arguments:

$ sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia

Password:

Usage: createinstallmedia --volume <path to volume to convert>

Arguments

--volume, A path to a volume that can be unmounted and erased to create the install media.

--nointeraction, Erase the disk pointed to by volume without prompting for confirmation.

--downloadassets, Download on-demand assets that may be required for installation.

Example: createinstallmedia --volume /Volumes/Untitled

I have run the above process over 3 times now. each time downloading a new Big Sur installer App. Each time the same errors. I have also tried installing to a disk container with the same results. Just as an experiment I tried installing Catalina and it worked just fine.

Any ideas as to what may be the issue?

And how should I go about downloading the full size image, not this smaller installer program?

Please reverify the Big Sur Application Size 37,479,165 bytes (20.6 MB on disk). This is not close to the correct size. Should be about 12.24 GB in size

Definitely, re-download the installer. Delete /Application/Install macOS Big Sur and re-download it using the Terminal as leroydouglas recommends. Sounds like you ended up with a stub installer which is not the full thing. You need the full sized download.

You keep downloading the stub installer for some unknown reason. It should be about 12GB's not 37.5MB.

There is a script written by the Greg Neagle - Sr. Systems Engineer @ Walt Disney Animation Studios. He's responsible for the Mac management tool, Munki. The Python script is an alternative method to download a macOS installer with the intention of packaging it for distribution via Munki.

Search Google for "installinstallmacos.py" you will find it on the Munki GitHub macadamia-scripts.

Show the raw source, copy and paste into a code editor and save it to a working folder in your home directory.

Make it executable with chmod +x

Execute it thusly:

./installinstallmacos.py --raw

It will create a Contents folder and scan the Apple distribution CDN, download some metadata then give you a menu to choose your macOS version. #1 is always the latest. It will then download and create a disk image. The files come directly from Apple's servers and the closest one to you will be utilized.

hdiutil attach <name of the disk image>
cd /Volumes/<name of the disk image>/Applications/
mv "Install macOS Big Sur" /Applications
cd ~
hdiutil detach /Volumes/<name of the disk image>

I have no idea why the stub is offered seemingly at random. If you were to run the stub it will download the rest of the missing files but then it's going to reboot automatically and try to install them. This method works every single time I've run into the dreaded macOS Installer stub being downloaded instead of the full installer. The stub installer is a rather common problem and this is the only way I've been able to download it on a system that only seems to want to download the stub instead of the full installation. It's very strange, I run into the issue now and then. One Mac will be fine and the next will only receive the stub and a 3rd Mac all the same network will grab the full installer. My guess is some corrupted AppStore cache or something like that.

Phillybass wrote:

SUCCESS!!

This command worked for me to download the full installer:

$ sudo softwareupdate --download --fetch-full-installer --full-installer-version 11.6

I do not know if it was the --download or the sudo (or both)

It was neither. If you are running a previous OS version, it will always download the “stub” installer. In that situation, the only way to get the full installer is to use the softwareupdate command as you did.