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I am trying to use Bootcamp to generate a Windows 10 USB key (64GB). I use Diskutil to initialize the key as MS-DOS FAT with MBR. The Bootcamp Assistant selecting the three options on the dialog box. It all works fine, but when I use the key to boot and finish the installation it tells me it cannot install Windows on that partition and that it needs an NTFS partition instead.

Thing is, the partition was reformatted by Bootcamp Assistant itself before copying the WindowsSupport software to it:

Macbookpro-2:~ silvano$ diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.3 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage Macbook HD              499.4 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3

/dev/disk1 (internal, virtual):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS Macbook HD             +499.0 GB   disk1
                                 Logical Volume on disk0s2
                                 69E26A69-CF3B-4E39-B7F9-BC8154952589
                                 Unencrypted

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *63.2 GB    disk2
   1:                 DOS_FAT_32 WININSTALL              63.2 GB    disk2s1

Below is the current state of my partitions. Partition 4 is where I am trying to install. I boot from EFI and it says it has an MBR, whereas he wants GPT.

Macbookpro-2:~ silvano$ diskutil list
/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.3 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage Macbook HD              451.4 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:       Microsoft Basic Data                         48.0 GB    disk0s4

/dev/disk1 (internal, virtual):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS Macbook HD             +451.0 GB   disk1
                                 Logical Volume on disk0s2
                                 69E26A69-CF3B-4E39-B7F9-BC8154952589
                                 Unencrypted

/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     FDisk_partition_scheme                        *16.0 GB    disk2
   1:                 DOS_FAT_32 WININSTALL              16.0 GB    disk2s1

Any tips welcome.

MBP 2013, Sierra 10.12.6

Silvano

David Anderson
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Silvano
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    I don't quite understand what you are asking. What does your question mean? You may consider to include Bootcamp in your title. –  Feb 07 '18 at 14:59
  • Are you looking to install Win10 on the 64GB USB volume? Because, if I remember correctly, you need an external volume to temporarily stuff the Bootcamp drivers onto and this can't be the same volume you are attempting to install onto. – 8None1 Feb 07 '18 at 15:49
  • I start Bootcamp assistant, it shows 3 steps, promising to initialize the USB key, download and install WindowsSupport and then install Windows. It goes away and it does the whole thing. So now I should have a bootable USB key. And it works. I can boot from it, but after selecting language, keyboard etc. it it tells me it is completing setup and it will install windows. Then it asks me for a partition to install it on, but none of the partitions shown works. It always says it needs an NTFS partition. But Bootcamp itself initialized the key as a FAT32. – Silvano Feb 07 '18 at 17:56
  • The boot camp generated media is just for drivers and such, not the installation itself. – Thorbjørn Ravn Andersen Oct 09 '18 at 00:00

2 Answers2

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To change the drive partitioning to a pure GPT format, enter the following commands. The commands may not make any sense to you, but the volume format can change the type of partitioning. 

sudo  diskutil  erasevolume  jhfs+  BootCamp  disk0s4
sudo  diskutil  erasevolume  FAT32  BOOTCAMP  disk0s4

From the description of your problem, below is what you need to do when you are asked about partitioning while installing Windows.

  1. Select the partition labeled BOOTCAMP.
  2. Click on the button labeled "Format". The BOOTCAMP label should disappear.
  3. Proceed to install Windows.

You have assumed the Boot Camp Assistant application can NTFS format a partition. If fact, it can not. Instead, the partition is FAT32 formatted with the label BOOTCAMP. You must click on the Format button during the Windows installation to NTFS format the partition. This removes the BOOTCAMP label. Later, when the Boot Camp Support Software is installed, the NTFS partition will be labeled BOOTCAMP.

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

David Anderson
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  • Thanx for the tip. I tried, and installed a 50GB partition on the HD as it requested. But that too, it was unable to install onto. So I clicked on format, and the message changed. Now it would not install because it was a MBR partition and he wanted a GPT. – Silvano Feb 07 '18 at 18:46
  • Update your output from diskutil list and I will post how to change to GPT. – David Anderson Feb 07 '18 at 18:58
  • Here it is. Partition 4 is where I intend to install Windows. Disk2 is the USB key. – Silvano Feb 08 '18 at 07:06
  • mmm... didn't fit in a comment. Will try with an answer. – Silvano Feb 08 '18 at 07:13
  • @Silvano: I updated my answer. The commands may not make any sense to you, but the volume format can change the type of partitioning. – David Anderson Feb 08 '18 at 14:59
  • Yup that worked. This time around the "format" made the parition OK to install Windows. Thank yo so much for your help! – Silvano Feb 08 '18 at 15:30
  • BTW: Normally, a Windows installation includes a Windows Recovery Environment (WRE) partition. Your installation will probably not create this partition. If not, the the content normally appearing in the WRE partition will be included in the BOOTCAMP partition. If you want a WRE partition, then you would have had to follows steps 2 through 10 of my answer to "Boot Camp Assistance is stuck on create a partition?". Sorry, I did not think of this sooner. – David Anderson Feb 08 '18 at 18:12
  • OK, so after successfully creating the partition on my MBP, I tried doing the same on my iMac, and this time it didn't work. Clicking the Format button keeps saying that he needs a GPT. So I tried formatting the partition as GPT to no avail, since Boot Camp Assistant will reformat it after me as MBR. Then I tried going manual according to the link above: "Boot Camp Assistance is stuck on create a partition?" but there diskutil does not know the verb "apfs" nor "resizeContainer". Am I running the wrong shell? – Silvano Feb 10 '18 at 10:46
  • Different Macs may have different requirements. Post a new question for your iMac. Include the year of the iMac and if possible the model identifier. Also, the version of macOS and the output from diskutil list. – David Anderson Feb 10 '18 at 11:08
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All that is way too involved. All you need to know is, when you get the error message, look at the options below the list box. One of the options is Format. Use it. You are now good to go.

Bernard Unger
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