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fabrizio

macrumors newbie
Original poster
Jan 28, 2005
22
7
Hello everyone.

I have been using Boot Camp on an external USB drive for months on Mojave without any problems. I could open Startup Disk, select the external Boot Camp drive, and reboot my Mac from there into Windows.

Now, just upgraded to Catalina, and the very same USB drive doesn't appear anymore inside the Startup Disk window.

Why's that? Any ideas?

Thanks in advance for any help.

Regards,
Fab.
 

chabig

macrumors 604
Sep 6, 2002
7,924
5,265
Launch Catalina’s Boot Camp assistant and see if it wants to update your USB drive?
 
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Boneheadxan

macrumors regular
Jul 19, 2009
143
28
I have the same issue. T3 SSD with Windows 10 doesn't show up as a boot option. The drive shows up in macOS but holding 'Alt' at boot doesn't work and neither does it show up in 'Startup Disk'.
 
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fabrizio

macrumors newbie
Original poster
Jan 28, 2005
22
7
Did you setup the new Mac OS did you setup the Finder Preference to see network attached storage checkmark?

I don't have such an option. Everything is checked and I can see the external drive mounting correctly on the Mac OS Desktop, but I am unable to see it inside the Startup Disk panel in order to reboot from Windows.

Thanks for your suggestion.
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Launch Catalina’s Boot Camp assistant and see if it wants to update your USB drive?

No, Boot Camp Assistant tells me to disconnect any external drive in order to proceed, therefore it is useless :(
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Samsung T5s probably aren’t bootable on T2 Macs. The T3 might be similar.

https://bombich.com/kb/ccc5/help-my-clone-wont-boot

My MacBook Pro is a 15" 2016, therefore I don't think that applies... and in any case, everything worked great with Mojave!
 
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fabrizio

macrumors newbie
Original poster
Jan 28, 2005
22
7
Anyone else having the same problem? Or being able to solve it?
 
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blackmagic1804

macrumors newbie
Dec 23, 2019
1
1
Ok, folks, I figured it out. I had to give full disk access to System Preferences inside the System Preferences >> Security & Privacy > Privacy tab.

I hope this can help someone else!

Thanks! I've been working on this for a day or two and your post helped!
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The one other thing I did was boot into the recovery partition and ran the Startup Security Utility to allow booting from external drives. I don't know if this was required or not.
https://support.apple.com/en-us/HT208198
 
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MrSimmo

macrumors member
Oct 17, 2014
35
14
Hi all, resurrecting this as I'm stuck:


I've used Virtualbox to load on Windows 10 x64 Home to an external USB flash stick.

I used the guide here https://medium.com/@SteveAA/hi-guys...tbe-able-a-few-with-their-errors-dafec1e44d12 and https://hackernoon.com/how-to-run-bootcamp-windows-10-on-a-usb3-86551dc3def8 .

I've downloaded the BootCamp drivers using Brigadier (from https://github.com/timsutton/brigadier) ; but have not installed them yet (mainly as I've not been able to boot into Windows yet).

I used an entire USB stick, i.e. GPT partition table, no other volumes/partitions and let Windows do its thing during install.

I've also enabled booting from external drives in the recovery mode (guide https://support.apple.com/en-us/HT208198) - the drive didn't show up until I did this stage.

From the above post (from fabrizio) I also added 'System Preferences' to the Full Disk Access section in Security and Privacy, but that didn't make a difference for me.

I've got a Macbook Pro 16", stock with Catalina 10.15.3 on it. The USB drive is a Patriot 256gb (600mb/sec) USB-A stick connected with a USB-A to USB-C lead from Amazon.

No errors occurred during any of the install stages.


Holding down Option to get into the boot menu. When I select 'EFI Boot' from the boot menu, it just goes into the Mac 'Startup Disk' utility. It can see both the 'Untitled Windows' and the 'Macintosh HD Encrypted Disk' listed but when I select 'Untitled Windows' it brings up the error "You can't change the startup disk to the selected disk. The bless tool was unable to set the current boot disk.".


Does anyone have any ideas?


Cheers, Andy
 
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Jules2010

macrumors member
Apr 7, 2010
34
0
I need to do this in the next day or too, so will report back, having issues...

First use the book camp utility to write the windows 10 iso to a usb stick, then selecting efi boot.

And managed to get the windows 10 pro installer to install windows.

I then have to restart / reboot and if I select the bootable EFI device (my external drive) I get windows boot issues, BCD etc.

My Macbook Pro is mid 2012 and doesn’t have the security chip used by the startup security utility, so that’s disable anyway.

What do I have to give ‘full disk access my too?

I’m going to look at this next...

The wintousb program isn’t free for windows 10 pro and not sure if this will all work.
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Hmmm I’m going to try this...
 
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4two4

macrumors newbie
Feb 18, 2013
4
0
Ok, folks, I figured it out. I had to give full disk access to System Preferences inside the System Preferences >> Security & Privacy > Privacy tab.

I hope this can help someone else!
Definitely worked for me, many thanks.
 
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Maxim Krouk

macrumors newbie
Jun 11, 2020
1
0
Republic of Belarus
Hello, I also have issues with booting.


• Formatted my Samsung T5 SSD using exFat GUID Partition Map
• Prepared the drive with WinToUSB and copied BootCamp Assistant WindowsSupport folder
• Chosen `No security` and `Allow booting from external media` options from the recovery menu (https://support.apple.com/en-us/HT208198)
• After choosing EFI Boot when booting with `option` key I'm getting apple logo and "The version of macOS on the selected disk needs to be reinstalled" alert

- I can select something like "Boot from WinToUSB drive with Windows operation system" from Startup Disk Utility but getting the same alert on restart.
- With Full Disk Access for System Preferences, I can also select my SSD as a startup disk, but getting the same error...

Maybe the problem is really Samsung T5, I'll try another SSD soon 🌚
 
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killamanshank1

macrumors newbie
Oct 13, 2020
1
0
Ok, folks, I figured it out. I had to give full disk access to System Preferences inside the System Preferences >> Security & Privacy > Privacy tab.

I hope this can help someone else!
Thank you so much for your help. I literally made an account to say thanks.
 
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