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I am trying to install Windows 10 on my iMac 27" (Mid 2011 - iMac12,2 - 3.4GHz -Core I7, OSX 10.11.6). When rebooting with the WININSTALL key, Windows Setup stops as it says it cannot install on the BootCamp Assistant generated partition (it is FAT32, wants NTFS). So I click the Formatbutton and he now says that the partition is MBR and he wants a GPT. So how do I make a GPT?

Note: Regarding the Boot Camp Assistant application: I modified the info.plist file by removing the "Pre" in ' "PreUSBBootSupportedModels" ' so I could get the checkbox to install Windows on the key.

Next question, I tried partitioning manually as suggested in question: Boot Camp Assistance is stuck on create a partition?, but the command:

sudo  diskutil  apfs  resizeContainer  disk0s2  180.8G  FAT32  BOOTCAMP  70G

fails as diskutil does not understand verbs apfs nor resizeContainer.
So I checked on my MBP running High Sierra and there apfs exists but not resizeContainer. Should I upgrade the iMac to High Sierra?

Here is my diskutil list:

diskutil list:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            967.3 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:       Microsoft Basic Data BOOTCAMP                32.0 GB    disk0s5

Here is a list of my WININSTALL:

total 3968
drwxrwxrwx  1 silvano  staff    32768 Feb  1  2014 $WinPEDriver$
-rwxrwxrwx  1 silvano  staff     3219 Feb  1  2014 AutoUnattend.xml
drwxrwxrwx  1 silvano  staff    32768 Feb  1  2014 BootCamp
-rwxrwxrwx  1 silvano  staff      128 Sep 30 18:00 autorun.inf
drwxrwxrwx  1 silvano  staff    32768 Sep 30 19:15 boot
-rwxrwxrwx  1 silvano  staff   397752 Sep 30 17:55 bootmgr
-rwxrwxrwx  1 silvano  staff  1236376 Sep 30 18:00 bootmgr.efi
drwxrwxrwx  1 silvano  staff    32768 Sep 30 19:15 efi
-rwxrwxrwx  1 silvano  staff    80696 Sep 30 18:00 setup.exe
drwxrwxrwx  1 silvano  staff    32768 Sep 30 19:15 sources
drwxrwxrwx  1 silvano  staff    32768 Sep 30 19:15 support
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    Are you using a USB flash drive instead of a DVD to install Windows? If you are using a USB flash drive, then what means did you use to put the installation software on the flash drive? Also, what computer did you use? – David Anderson Feb 10 '18 at 12:20
  • I'm actually using a blank HD, because it's faster than a USB key. I put Windows 10 and Windows Support on it with BootCamp Assistant. I did the same for my MBP and there it worked fine. – Silvano Feb 10 '18 at 12:37
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    So, you were able to use the Boot Camp Assistant on the 2011 iMac to transfer the Windows 10 files from the ISO to an external drive and download the Boot Camp Support Software from the internet to the same external drive? You did this without modifying the Boot Camp Assistant application in any way? – David Anderson Feb 10 '18 at 13:26
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    I modified the info.plist file by removing the "Pre" in '<key> "PreUSBBootSupportedModels" ' so I could get the checkbox to install Windows on the key. – Silvano Feb 10 '18 at 13:41
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    Now we are getting somewhere. You might have mentioned that in your question. The path you have chosen will eventually lead to failure. Usually, the resulting install will not boot or some hardware will not work properly. There are various other ways to use an external disk to install Windows on a 2011 iMac. Before I post an answer, let me ask: Why did you not use a Windows 10 DVD to install? – David Anderson Feb 10 '18 at 14:15
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Your best course of action would be to install Windows 10 the same way Apple instructs you to install Windows 8.1. For these instructions, see the Apple website: Use Windows 8.1 on your Mac with Boot Camp. When using these instructions to install Windows 10, you might want to consider the following.

  • You need to burn the Windows ISO file to a DVD. Some Windows 10 ISO files are large enough that you will need a double layer (DL) DVD. Older versions of OS X used the Disk Utility application to burn the contents of an ISO file to a DVD. With the newer versions of macOS (OS X), you can burn the contents of an ISO file to a DVD directly from a Finder application window. You use the Boot Camp Assistant to download the Boot Camp Support Software to an external drive.
  • You already have a BOOTCAMP partition. Assuming your external drive installer has the correct Boot Camp Support Software, you should be able to install Windows 10 with using the Boot Camp Assistant. Insert the DVD and connect the external drive, restart the iMac and then immediately hold down the option key. When the DVD icon labeled "Windows" appears, select the icon then the arrow below the icon. If during installation, you boot back to macOS (OS X), goto Startup Disk under System Preferences. Select the Windows partition, then restart the iMac to continue installation.

If you do not want to use a DVD, then you can use the accepted answer to the question: How to install Windows 10 into a 2011 iMac without using the Boot Camp Assistant, an optical (DVD) drive or third party tools?. If you are using OSX 10.11.6, then you can skip step 3.


To be clear, Windows installations on this model Mac must use the legacy BIOS boot method. This requires the installation drive to contain partition entries in both the Master Boot Record (MBR) table and the GUID Partition Table (GPT). Windows will only see the MBR table entries and macOS (OS X) will only see the GPT entries. Therefore, Windows with think the drive is MBR partitioned, while macOS (OS X) will think the drive is GPT partitioned.

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    Thank you very much for these clear instructions. Guess I'll try the method with no DVD because my iMac's DVD player is broken and I live in Africa, so it takes me min. 4 weeks to get a new one. – Silvano Feb 10 '18 at 19:50
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    You made a mistake somewhere. Step 7 renames AutoUnattend.xml to NoAutoUnattend.xml. I do not see this change in your posted output. This change causes "Repair your computer" to appear. – David Anderson Feb 11 '18 at 10:03
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    Step 7 renames AutoUnattend.xml on BOOTCAMP. Step 8 copies from BOOTCAMP to WINSTALL. Step 8 renames efi on BOOTCAMP. Therefore, efi does not get renamed on WINSTALL. If you did rename efi on WINSTALL, then you would not be able to boot from the external drive. – David Anderson Feb 11 '18 at 10:34
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    Of course. I skipped step 8 because I already had WININSTALL and oversaw the fact that I had renamed those 2 files on BOOTCAMP. May I ask, why do we need to have two identical copies of the installation kit? doesn't BOOTCAMP get reformatted/overwritten during the Windows setup? – Silvano Feb 11 '18 at 11:05
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    The WINSTALL copy is for EFI booting and the BOOTCAMP copy is form BIOS booting. The Windows Installer will not install Windows unless the Mac is BIOS booted. You can not externally BIOS boot on Macs. Therefore, you need to first external EFI boot in order to setup an internal BIOS boot. In step 10, you EFI boot from the external drive partition labeled WINSTALL. In step 14, you BIOS boot from the internal drive partition labeled BOOTCAMP. – David Anderson Feb 11 '18 at 12:15

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