Installing Win10 on 2nd HD partition w/o Reformatting

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GTRBedros Author

Level 1

9 points

Installing Win10 on 2nd HD partition w/o Reformatting

I'm running latest Yosemite 10.10.4 (14E46) and attempting to install Windows 10 via BootCamp.

I have an iMac 27" Mid-2011, Core i5, 12gig Ram

I have two hard drives. Primary, OS X on 256GB SSD. Secondary drive is a 2TB HDD.

The second 2TB drive is divided into 3 partitions, 1TB, 500GB, 500GB

On the first two partitions I have photos, iTunes, and my documents. The 3rd partition is empty, but formatted etc..

What I want to do: Install Windows/BootCamp on my 2TD drive, in the empty 500GB partition.

Issue: BootCamp recognizes the 2TB drive, lists the names of the 3 partitions, but indicates it has unknown formatting and needs to reformat the entire drive. I cannot erase the other two partitions. Is there a way to manually format the 3rd partition for BootCamp to accept?

iMac, OS X Yosemite (10.10.3)

Posted on Aug 3, 2015 7:53 PM

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Answer 1

GTRBedros Author

Level 1

9 points

Aug 3, 2015 8:21 PM in response to GTRBedros

Here is a screen shot. The 3 patrons are listed; Cayman, Carrera, WIN10. I want to install on WIN10 partition.

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Answer 2

Loner T

Level 9

59,471 points

Aug 3, 2015 9:01 PM in response to GTRBedros

You cannot use BC Assistant for this.

1. Does your Mac have a built-in Optical drive?

2. Does BCA provide an option create a USB installer?

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Answer 3

GTRBedros Author

Level 1

9 points

Aug 4, 2015 7:34 PM in response to Loner T

It does have an optical drive. But my windows 10 installation is an ISO file on my computer. I was planning to create a USB boot drive, but instructions indicate that BC Assistant will do this, right after I tell it what drive/partition to install it to.

BC Assistance did ask me where to copy the updated Microsoft installation files, which I pointed to 32GB USB drive formatted in MS-DOS. drive I was planning to use for the installation.

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Answer 4

Loner T

Level 9

59,471 points

Aug 4, 2015 7:39 PM in response to GTRBedros

Did you edit Bootcamp info.plist?

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Answer 5

GTRBedros Author

Level 1

9 points

Aug 4, 2015 9:44 PM in response to Loner T

I have not and I can't find it in my ~/Library/Preferences folder

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Answer 6

Loner T

Level 9

59,471 points

Aug 4, 2015 9:49 PM in response to GTRBedros

In BC Assistant, how many options do you see? Two or Three?

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Answer 7

GTRBedros Author

Level 1

9 points

Aug 4, 2015 10:27 PM in response to Loner T

Here are the initial screens in BC.

I keep everything checked...download updates and install windows

Then I'm asked where to save the updates. I'm given my external USB drive (Time machine backup) and the 32GB Patriot USB drive.

BC starts to download the updates...

Afterwards I'm at my original screen capture of where to install windows.

Does this help??? thank you for helping out! much appreciated.

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Answer 8

Loner T

Level 9

59,471 points

Aug 5, 2015 4:28 AM in response to GTRBedros

Yes, this helps. Please post the output of the following Terminal commands.

diskutil list

diskutil cs list

sudo gpt -vv -r show /dev/diskN (N should be chosen from the output of the first command and must point to the 2Tb disk).

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Answer 9

GTRBedros Author

Level 1

9 points

Aug 5, 2015 8:13 PM in response to Loner T

All 3 commands in order.

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Answer 10

Loner T

Level 9

59,471 points

Aug 5, 2015 8:33 PM in response to GTRBedros

The following steps create a Hybrid MBR and point to the W10 as the candidate for Windows installation on disk1.

Rebuild MBR to match the new GPT information thus resetting the Hybrid MBR. Use defaults for other questions (like partition codes). The only values that need modifications are the Boot flags and step 10. Accept all other defaults that Gdisk offers. Please see thesample Q&A as an example. These steps can be repeated if you make a mistake before you get to Step 12, otherwise start from Step 1 for these steps. Step 6 has numbers which are typed with a space between the numbers.

Sudo gdisk /dev/rdisk1
P (Print list of parts)
R (Recover)
O (print current Hybrid MBR)
H (chooses Hybrid)
Partitions numbers to be hybridized: 2 3 4
Y (Good for GRUB question)
N (part 2 boot flag)
N (part 3 boot flag)
Y (part 4 boot flag make NTFS bootable partition)
O (print current Hybrid MBR)
W (Write the new MBR)
Y (Yes! write the new MBR)
Reboot
Use the BCA-created USB to boot from and select disk1/partition4 as the destination for Windows.

Please disconnect all external disks except the USB, KVM. Do not use any USB hubs.

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Answer 11

GTRBedros Author

Level 1

9 points

Aug 6, 2015 8:54 PM in response to Loner T

followed it exactly. Brings me to same setup options afterwards.

I went back and formatted the WIN10 partition again from MS-DOS to Mac Journaled

I'm not copying the ISO image to the USB drive manually using dd command

I'll go back and try your steps again with the new formatted drive

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Answer 12

GTRBedros Author

Level 1

9 points

Aug 6, 2015 9:12 PM in response to GTRBedros

Here is the disk list after performing the steps above. I did remove my timemachine external drive and USB. Only two internal drives are shown. Also, the USB boot drive I created is not readable.

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Answer 13

Aug 7, 2015 7:36 AM in response to GTRBedros

IMO you are going to a lot of trouble to install an unsupported OS. There are not yet any Windows 10 Boot Camp drivers so even it you succeed in getting Windows 10 installed it is doubtful it will work 100%.

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