usb flashdrive will not boot on mac

Question

usb flashdrive will not boot on mac

I have a Retina 5K Imac circa 214 (system report says "15,1"). Trying to boot from an USB flash drive formatted as MacOS extended (journaled) and GUID Partition Map. Ran "disk utility" on top-level USB disk , it showed bootable=NO. However, disk utility shows "bootable=YES" if I run it on the partition on the USB disk. If I reboot and hold down the Option key I do not see the USB flash drive. I also don't see it on using System Preference's Startup Disk item. Ran "First Aid" from disk utility on both he top-level USB disk and the partition and it does not show anything wrong. I have "Install MacOs Monterey.app" on the USB flash drive. I am running Big Sur on the iMac. Any suggestions?

iMac Line (2012 and Later)

Posted on Jan 29, 2022 9:36 AM

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Answer 1

Top-ranking reply

HWTech

Level 9

60,452 points

Jan 31, 2022 10:27 AM in response to erickdobrasil

Read those instructions again, this time more carefully. If you want to create a bootable macOS USB installer you need to use the command line to do so. Copying the "Install MacOs Monterey.app" does just that....it copies the app which is just a standard application with no ability to boot a computer.

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Answer 2

Jan 31, 2022 10:44 AM in response to HWTech

I repeated the process as specified in the document but my Imac, on reboot and holding down the option key, still does not show the usb flashdrive as a bootable disk. It only shows my Imac’s hard drive.

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Answer 3

HWTech

Level 9

60,452 points

Jan 31, 2022 11:31 AM in response to erickdobrasil

Sorry, I didn't realize that A "15.1" iMac is either a "Late 2014" or an "Early 2015" model which is not officially compatible or supported with macOS 12.x Monterey. You will not be able to install Monterey to this iMac using these instructions. You can, however, run macOS 11.x Big Sur on your iMac.

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Answer 4

Jan 31, 2022 1:08 PM in response to HWTech

I also tried installing Big Sur using my usb flashdrive but I still cannot get my usb flashdrive to show up as a boot disk after rebooting my imac and holding down the Option key. Only my Imac’s hard drive shows up as a boot device, not the USB flashdrive. I also tried the flashdrive on another USB port, with the same result.

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Answer 5

HWTech

Level 9

60,452 points

Jan 31, 2022 4:38 PM in response to erickdobrasil

Try using a different USB stick especially a different brand. The quality of USB sticks is extremely poor and Macs can be very particular about the drives used for booting. Also make sure the USB stick was properly erased as GUID partition and MacOS Extended (Journaled) before you issues the Terminal commands to create the bootable macOS USB installer. If you left the USB stick using the MBR partition type (default partition type when purchased), then it won't boot.

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Answer 6

Jan 31, 2022 5:42 PM in response to HWTech

I appreciate your response, thank you. I did erase the USB stick properly w GUID partition and Mac extended (journaled) partition. I think I will try the stick on another Imac in the family when I get a chance. If it fails there then I will try another USB stick.

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Answer 7

rkaufmann87

Level 10

143,958 points

Jan 29, 2022 9:48 AM in response to erickdobrasil

Have you reviewed Apple's instructions in https://support.apple.com/en-us/HT201372?

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Answer 8

Jan 29, 2022 11:59 AM in response to rkaufmann87

Thanks for the reply. Yes, I followed all the steps in the document you refer to. The USB flashdrive still will not boot.

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usb flashdrive will not boot on mac

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