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External ssd not showing in Startup Disk, trying to install big sur for trial.

External ssd not showing in Startup Disk, trying to install Big Sur for trial as detailed in Apple support pages. Mac is Late 2014 pre T2 type with Mojave 10.14.6 installed on internal SSD.

I have tried formatting the external SSD in APFS, APFS encrypted, and with one and two volumes, these all show in Disc utilities and can be written to and used the normal way, but they do not show up as an option in Recovery mode part from an encrypted volume when there was more than one Volume on the ext SSD, and even then once the Volume Password was entered the ssd vanished.

I have disconnected other drives and as far as I can tell there is no Startup Security Utility in the Recovery App.

Any thoughts or help would be greatly appreciated.

iMac 27″, macOS 10.14

Posted on Jan 30, 2021 9:31 AM

Reply
Question marked as Top-ranking reply

Posted on Feb 2, 2021 9:11 AM

Re       Update


Hi,

This is a reply to all those who have tried to help and as an aid for others who may want to download another MacOS to an external blank drive for trial or as an essential always available backup system drive.

In addition to the method stated previously I thought it might be possible to create a bootable drive that would be recognised by Startup in recovery mode but the support pages covered instructions only for system administrators needing to install the OS on a lot of machines, it meant more time on my part and using terminal instructions with no certainty of success.


I therefore contacted Apple support who were very helpful and advised that sometimes external drives are not recognised for Startup even though they appear to be normal in Disk Utility, this could be due to drive or formatting errors, cables or connections, or ports on the Mac; so these are the steps taken for my iMac ( Intel processor, no T2 chip, no Startup Security Utility, internal & external SSDs) using Internet Recovery:-


1.             Check backups available on separate drive

2.             Reset System Management Controller to discharge all residual energy from ports. See 

https://support.apple.com/en-gb/HT201295 )

in addition click Start Button 5 times before reconnecting cables and restart.

3.             Restart as normal and re-enable Finder in iCloud if necessary.

4.             Shutdown and Restart into Internet Recovery manually, at Startup press and hold Shift-Option-Command-R

until the spinning globe appears then:-

a.    Make sure the language selected matches your keyboard.

b.    Check upper right to make sure you have an Internet connection.

c.     Access Disk Utility, highlight the external drive you want to use and select erase. In the dropdown boxes enter

                                               i.     Name             e.g. MyVolume, Big Sur etc.

                                             ii.     Format           APFS (assuming its an SSD)

                                            iii.     Scheme         GUID Partition Map

d.    Execute and check it’s successful, in the Side Bar it should show the original Drive Name, a Container, and a Volume with the name you entered above with free space very nearly equal to the size of the SSD. If the drive also shows other volumes with same capacity it probably doesn’t matter these ghost volumes probably wont appear when using the system Disk Utility nor affect the procedure.  For more information About MacOS Recovery on Intel-based Mac computers see https://support.apple.com/en-gb/HT201314

5.             Close the Disk Utility and open Startup (top left menu), you should see and be able to select your new ssd volume

and close.

6.             From the Utilities Window chose the MacOS you want, this should give you the option to confirm the download

destination.

7.             The download will probably take 40 min or more.

8.             On completion Shutdown and then Press and hold the Option key as you start up your Mac.

If you want to change the default Startup Disk you will need to change the drive selected in the Startup Utility in System preferences. See https://support.apple.com/en-gb/guide/mac-help/mchlp1034/11.0/mac/11.0 )

Thank you to everyone that responded

Similar questions

15 replies
Question marked as Top-ranking reply

Feb 2, 2021 9:11 AM in response to Ogmoreman

Re       Update


Hi,

This is a reply to all those who have tried to help and as an aid for others who may want to download another MacOS to an external blank drive for trial or as an essential always available backup system drive.

In addition to the method stated previously I thought it might be possible to create a bootable drive that would be recognised by Startup in recovery mode but the support pages covered instructions only for system administrators needing to install the OS on a lot of machines, it meant more time on my part and using terminal instructions with no certainty of success.


I therefore contacted Apple support who were very helpful and advised that sometimes external drives are not recognised for Startup even though they appear to be normal in Disk Utility, this could be due to drive or formatting errors, cables or connections, or ports on the Mac; so these are the steps taken for my iMac ( Intel processor, no T2 chip, no Startup Security Utility, internal & external SSDs) using Internet Recovery:-


1.             Check backups available on separate drive

2.             Reset System Management Controller to discharge all residual energy from ports. See 

https://support.apple.com/en-gb/HT201295 )

in addition click Start Button 5 times before reconnecting cables and restart.

3.             Restart as normal and re-enable Finder in iCloud if necessary.

4.             Shutdown and Restart into Internet Recovery manually, at Startup press and hold Shift-Option-Command-R

until the spinning globe appears then:-

a.    Make sure the language selected matches your keyboard.

b.    Check upper right to make sure you have an Internet connection.

c.     Access Disk Utility, highlight the external drive you want to use and select erase. In the dropdown boxes enter

                                               i.     Name             e.g. MyVolume, Big Sur etc.

                                             ii.     Format           APFS (assuming its an SSD)

                                            iii.     Scheme         GUID Partition Map

d.    Execute and check it’s successful, in the Side Bar it should show the original Drive Name, a Container, and a Volume with the name you entered above with free space very nearly equal to the size of the SSD. If the drive also shows other volumes with same capacity it probably doesn’t matter these ghost volumes probably wont appear when using the system Disk Utility nor affect the procedure.  For more information About MacOS Recovery on Intel-based Mac computers see https://support.apple.com/en-gb/HT201314

5.             Close the Disk Utility and open Startup (top left menu), you should see and be able to select your new ssd volume

and close.

6.             From the Utilities Window chose the MacOS you want, this should give you the option to confirm the download

destination.

7.             The download will probably take 40 min or more.

8.             On completion Shutdown and then Press and hold the Option key as you start up your Mac.

If you want to change the default Startup Disk you will need to change the drive selected in the Startup Utility in System preferences. See https://support.apple.com/en-gb/guide/mac-help/mchlp1034/11.0/mac/11.0 )

Thank you to everyone that responded

Feb 1, 2021 8:48 AM in response to Ogmoreman

Within Disk Utility make sure to select the physical drive and erase it as GUID partition and APFS (top option). Don't use the encrypted option if it will be a macOS boot drive. Enable encryption later using Filevault.


Disk Utility hides the physical drive from view so you must first click on "View" within Disk Utility and select "Show All Devices" so that the physical drive appears on the left pane of Disk Utility. This Apple article has a section showing how to reveal the physical drive within Disk Utility:

https://support.apple.com/guide/disk-utility/erase-and-reformat-a-storage-device-dskutl14079/mac

Jan 30, 2021 1:32 PM in response to Ogmoreman

Are you using any third party software to manage your external drive? Keep in mind this third party software is not available when you boot into Recovery Mode. If you are using third party software to use the hardware encryption feature of the external SSD, then you need to disable the hardware encryption on the external SSD.

Jan 31, 2021 11:24 AM in response to Ogmoreman

Ogmoreman wrote:

External ssd not showing in Startup Disk, trying to install Big Sur for trial as detailed in Apple support pages. Mac is Late 2014 pre T2 type with Mojave 10.14.6 installed on internal SSD.
I have tried formatting the external SSD in APFS, APFS encrypted, and with one and two volumes, these all show in Disc utilities and can be written to and used the normal way, but they do not show up as an option in Recovery mode part from an encrypted volume when there was more than one Volume on the ext SSD, and even then once the Volume Password was entered the ssd vanished.
I have disconnected other drives and as far as I can tell there is no Startup Security Utility in the Recovery App.
Any thoughts or help would be greatly appreciated.

The disk won't be listed as an option for booting unless you have a properly installed operating system there. How did you install the operating system on the external drive?


Assuming you did install it properly, see this article for a list of reasons an external drive won't boot and things you can do to fix it.


https://bombich.com/kb/ccc4/help-my-clone-wont-boot

Feb 1, 2021 1:46 AM in response to steve626

Hi HWTech

Thanks for the thought, I haven't ever used any third party software, the drive is a Western Digital My Passport SSD 1TB NVMe USB Gen 2 & Gen 1, connected via USB 3.0 port (no type C on my Mac). The WD utilities were deleted and the Drive has been erased and reformatted many times via Disk Utilities, and at the time of trying to install Big Sur it held no data.

External ssd not showing in Startup Disk, trying to install big sur for trial.

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