createinstallmedia NOT creating a bootable USB

Question

createinstallmedia NOT creating a bootable USB

I followed the instructions on https://support.apple.com/sl-si/HT201372 to create a bootable installer for macOS Catalina. The process completes without error but the resulting USB disk is not bootable. If I open it with the finder the lone file on the drive has a circle with line through it and if I go to the Startup Disk System Preference the USB devices is not shown or able to be selected as a boot device. What could be the problem? The installer app was freshly downloaded today onto a late 2013 iMac already running Catalina 10.15.1.

Posted on Nov 13, 2019 5:44 PM

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Answer 1

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leroydouglas

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Nov 13, 2019 6:11 PM in response to Larry Jorgenson

From Terminal you should see something similar if you, copy and paste:

diskutil list

/dev/disk2 (external, physical):

#: TYPE NAME SIZE IDENTIFIER

0: GUID_partition_scheme *16.0 GB disk2

1: EFI EFI 209.7 MB disk2s1

2: Apple_HFS Install macOS Catalina 15.7 GB disk2s2

Seems like you have all the information in your link: https://support.apple.com/sl-si/HT201372

You can verify the details, you can try a different USB thumb drive.

I would try again.

You can reformat the USBdrive w/ Disk Utility.app>View>Show All Devices>>External> your brand of USB

as GUID (GPT) / HFS+ (extended journaled)

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Answer 2

Nov 13, 2019 7:14 PM in response to leroydouglas

OK, I am dumb. I think the problem was that the USB stick I was using was only a 8GB. This used to work with prior versions but Catalina now requires a 16 GB stick (as stated in the KB). Oops. Anyway, I don't recall seeing any particular error messages or failure notifications from terminal when I used the 8GB but when I used the 16GB I clearly see a more successful conclusion:

Erasing disk: 0%... 10%... 20%... 30%... 100%

Copying to disk: 0%... 10%... 20%... 30%... 40%... 50%... 60%... 70%... 80%... 90%... 100%

Making disk bootable...

Copying boot files...

Install media now available at "/Volumes/Install macOS Catalina"

Problem solved.

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