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Question: Option Startup not working since upgrading to High Sierra

I have a 2017 iMac with an internal SSD. I have Bootcamp Windows 10 on an external USB 3 SSD. On OS X Sierra, I would Option-Startup and select the EFI drive and boot into Windows 10. I just upgraded the iMac to High Sierra and Option-Startup no longer works. No boot drive selection is displayed.

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Dec 24, 2017 7:01 AM in response to jtconte In response to jtconte

High Sierra has several security and EFI fixes, which break what you could do in Sierra. The external disk complicates this further. As a test, install Sierra on an external disk, and boot from it. Once booted in Sierra, select the external disk in Startup Disks and test.

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Dec 18, 2017 7:04 AM in response to Loner T In response to Loner T

Thanks Loner T. I tried that and the very first re-boot holding the Option key gives the boot drive screen but only shows the Macintosh HD. Subsequent re-boots ignore the Option key.

I contacted Apple support and they are looking into it and are supposed to get back to me in a few days.

Dec 18, 2017 7:04 AM

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Dec 21, 2017 5:08 PM in response to Loner T In response to Loner T

Yes, it shows BOOTCAMP Windows and the Macintosh HD macOS, 10.13.2 drives but when I select the Bootcamp drive and click Restart the message that the bless tool was unable to set the current boot disk comes up.


Support sent me an email stating no further help since an external boot drive is unsupported.

Dec 21, 2017 5:08 PM

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Dec 24, 2017 7:01 AM in response to jtconte In response to jtconte

High Sierra has several security and EFI fixes, which break what you could do in Sierra. The external disk complicates this further. As a test, install Sierra on an external disk, and boot from it. Once booted in Sierra, select the external disk in Startup Disks and test.

Dec 24, 2017 7:01 AM

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Dec 24, 2017 7:12 AM in response to Loner T In response to Loner T

I appreciate the test steps Loner T. I may give that a try and post the results. I have to admit that I am leaning towards abandoning the external Windows drive. It is just too much effort and Windows 10 would not allow a major update because it was on an external drive so ....


Do you know how safe putting Windows 10 on my iMac's internal, High Sierra SSD would be?

Dec 24, 2017 7:12 AM

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Jan 19, 2018 9:14 AM in response to jtconte In response to jtconte

High Sierra has some specific issues when partitioning the internal disk, but all issues can be addressed. It is relatively safe. Regular backups are critical for a setup using the internal disk.

Jan 19, 2018 9:14 AM

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Dec 24, 2017 1:17 PM in response to jtconte In response to jtconte

Try this, it may fix your problem. I have a SSD installed in a PCI slot on my old mac pro, I can boot to either OSX High Sierra or Windows but only by holding the option/alt key at bootup. Apple doesent currently support using bootcamp control panel to boot between them, due to High Sierra using the AFPS file system.


About Startup Security Utility - Apple Support

Dec 24, 2017 1:17 PM

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Dec 25, 2017 7:01 AM in response to What2be1 In response to What2be1

The current version of Bootcamp.exe does not understand the APFS structure. HS converts most solid-state disks to APFS, unless you use Using the macOS High Sierra OS installer’s startosinstall tool to avoid APFS conversion | Der Flounder .

Dec 25, 2017 7:01 AM

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Jan 19, 2018 8:34 AM in response to jtconte In response to jtconte

I have the High Sierra version and having an issue to get windows to boot from an external SSD. After completing all the steps necessary to install windows on the SSD, when I tried to restart using the startup disk, the error came up "You can’t change the startup disk to the selected disk. The bless tool was unable to set the current boot disk." I tried the NVRAM reset, but it didn't do anything. Please help!!

Jan 19, 2018 8:34 AM

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Question: Option Startup not working since upgrading to High Sierra