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USB Mojave Install bootable Flash drive instructions creates vicious circle.

When attempting to install a bootable USB Mojave installer, after downloading the installer and following the instructions given on the Apple support page


I followed these instructions, but after step 4 I got a message saying I must download the installer (I have already) and go to this page (the Apple Support page detailing the instructions I was following....possibly the one you are reading). HELP!


Here is the message in its entirety: To use this tool, you must download the macOS installer application on a Mac with 10.12.5 or later, or El Capitan 10.11.6. For more information, please see the following: https://support.apple.com/kb/HT201372.


Talk about a vicious circle! I used the instructions on this page and the terminal window tells me to come back to this page.

Posted on Sep 28, 2020 9:52 PM

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Posted on Sep 29, 2020 7:51 PM

Success. The terminal command method for formatting the USB installer worked after re-download. The Mojave install to the external drive over firewire took more than 2 hours. The external drive boots the MacBook Pro okay, with some weird glitches. For example if you go to the Start Up Disk preferences, you cannot choose the internal MacBook Pro SSD drive before restarting. I had to shut down, unplug the external drive, and then boot up. Normally you can just select the preferred boot drive and restart.


Thanks for the assistance!

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Sep 29, 2020 7:51 PM in response to Jason Eng1

Success. The terminal command method for formatting the USB installer worked after re-download. The Mojave install to the external drive over firewire took more than 2 hours. The external drive boots the MacBook Pro okay, with some weird glitches. For example if you go to the Start Up Disk preferences, you cannot choose the internal MacBook Pro SSD drive before restarting. I had to shut down, unplug the external drive, and then boot up. Normally you can just select the preferred boot drive and restart.


Thanks for the assistance!

Sep 29, 2020 7:49 AM in response to Eau Rouge

Thanks for your quick reply! I was not able to follow your advice.

  • you mentioned the installer should be 6.05 Gbs. My Mojave installer is 5.57 Gbs. It has failed consistently, returning the error "An error occurred while preparing the installation. Try running this application again." Since the file size seems to be wrong, maybe it is only partially downloaded. I also tried the Terminal command method and got the vicious circle. So I deleted it and tried to re-download the installer.
  • I have not been able to re-download the installer. The App Store app shows a popup button "Open" instead of "Download". It seems to think the installer is still in the Applications folder even though I have deleted it and emptied the trash. After several attempts to get to the Mojave installer page in the App Store, Safari and other browsers are now returning the Catalina update page instead. I don't understand that.
  • I also noticed that your instructions for using the sudo Terminal command shows the El Capitan installer. Is there a reason I should be using that instead of the Mojave installer or is that a typo?

Sep 29, 2020 8:34 AM in response to Jason Eng1

OOOPsy I posted the wrong Terminal instructions use the one for Mojave.


The full installer is 6.05GBs.

If the App store says Open it is detecting a copy of the Install macOS Mojave.app somewhere on your mac.

Do a search put it in your Trash and empty the Trash.

When downloading from Apple use a cabled connection, do not use the mac while it is downloading

or any other devices that share the same internet connection.


When you have created a bootable USB installer you can then use that to format the external drive

and then install Mojave.


When you boot to the USB stick click on Disk Utility and press Continue.


Click on View in the menubar and select Show All Devices.


Highlight the uppermost Disk in the External sector of the left hand field,

do not highlight any of the indented Volumes.

Click Erase.

Give the Disk a name.

Format: APFS

Scheme: GUID Partition Map.

Click Erase.

When that is done quit Disk Utility.


Click on Install OS and press Continue.

The installation should start, follow the prompts,

when it asks you to choose a disk for the installation

choose the external disk.


Do not install any manufacturer software on the external disk, this interferes with the macs

management of the disk.



Sep 29, 2020 12:43 AM in response to Jason Eng1

All you need to do is have the Install macOS Mojave.app in your Applications folder

it should be 6.05GBs in size. And a USB stick 16GBs or larger preferably called MyVolume.


Open Terminal and paste in this command


sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app


press Return

enter your Password

(your input will not be echoed on scree)

press Return


Follow the prompts.


Process takes about 20-30 minutes.


If your USB name has more than one word separated by spaces you would need to type it in as

/The\ USB\ Name.

Sep 29, 2020 8:22 AM in response to Jason Eng1

Update: I managed to get the installer. It is 6.05 Gbs. Will try again.


My goal is to create an external firewire boot drive running Mojave. Will update this issue again if it works.

Meanwhile I'd like to know if this is even possible! I have not found any info that confirms or denies this practice can work. Of course, this was certainly possible in past versions of MacOS X, but I've not done it in many years. I have legacy software that is unusable with anything newer than Sierra ( FileMaker 10, Final Cut Pro 7, QuickTime Pro 7), but I need Mojave to run Adobe CC's apps.

Sep 29, 2020 10:40 PM in response to Jason Eng1

The installation took along time, it should only take about 15-30 minutes, is the FireWire Drive plugged directly in to the mac

or are you using some sort of adaptor to plug the Firewire device to the mac.

Try this app on the drive, https://binaryfruit.com/drivedx to check the disks health, there is a free trial period.



What OS is your MacBook running.

Older OS's like El Capitan and Yosemite going backwards cannot see APFS formatted drives so that is why

your Firewire drive with Mojave cannot be seen in system Preferences> Startup Disk or on the Desktop.

To boot to the Mojave disk from El Capitan or earlier you need to Restart the mac while pressing the option/ alt key

and selecting the Mojave drive in the Startup Manager and pressing Return.

When restarting into an older OS with an APFS formatted disk connected you will get a warning the the disk is not readable by this computer, you will be asked to Ignore, Initialise or Cancel. Press Ignore, do not press Initialise this will reformat the APFS disk and erase all your data on it.

Sep 30, 2020 4:26 PM in response to Eau Rouge

Hey thanks for following up. Yes I have to use an Apple firewire 800 to Thunderbolt adapter since my Late 2013 MacBook Pro doesn't offer an FW800 interface. This would work better on a LaCie Thunderbolt drive -- I will use one later on if necessary. I'm using Sierra (I mentioned why in a previous post). Thirdly, the problem of not seeing the internal boot disk in system prefs happened while running my new Mojave system on the external drive. Since in that situation the APFS boot disk is the active system disk (Mojave), and I'm looking at Startup Disks to restart with Sierra, I was able to see the internal disk with Sierra, but could not select it for restart.

USB Mojave Install bootable Flash drive instructions creates vicious circle.

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