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How can I reinstall Boot Camp using an existing Windows partition?

Can I bring back the Windows option in the Boot Camp menu, using an existing Windows installation but a reinstalled OS X?


Here’s what I did:

  1. Bought a MBA mid-2012.
  2. Installed Windows 2012 using the standard Boot Camp procedure. It worked well.
  3. Reinstalled OS X Yosemite by removing the OS X main partition, recreating it and doing the standard OS X setup.


Now:

  • OS X works well.
  • The Windows partition seems unharmed: I can browse through all system and user files in Finder.
  • Pressing alt while booting brings up an OS menu, with only OS X as an option. Previously it would also show Windows.
  • When I launch Boot Camp Assistant, I only get three options: create an install disk / download support software / remove Windows.


I want to have Windows as a boot option again, using the installation that is still on my hard disk. I suspect it should be possible, but searching the forums for ‘reinstall Boot Camp menu’ I couldn’t find a way how.


In case it helps, here is my fdisk output:


$ sudo fdisk /dev/disk0

Password:

Disk: /dev/disk0 geometry: 30515/255/63 [490234752 sectors]

Signature: 0xAA55

Starting Ending

#: id cyl hd sec - cyl hd sec [ start - size]

------------------------------------------------------------------------

1: EE 1023 254 63 - 1023 254 63 [ 1 - 409639] <Unknown ID>

2: AC 1023 254 63 - 1023 254 63 [ 409640 - 406526136] <Unknown ID>

3: AB 1023 254 63 - 1023 254 63 [ 406935776 - 1269536] Darwin Boot

4: 0C 1023 254 63 - 1023 254 63 [ 408205312 - 82028544] Win95 FAT32L

MacBook Air, OS X Yosemite (10.10.4), FileVault, Windows 2012

Posted on Jul 6, 2015 12:00 AM

Reply
Question marked as Best reply

Posted on Jul 6, 2015 4:16 AM

Please ignore i386 MBR errors in the following steps. These steps correct the MBR and make MBR#4 bootable.


sudo fdisk -e /dev/disk0

p

setpid 4

07

flag 4

p

w

y


Reboot and test.


Please also the output of


diskutil list

diskutil cs list

sudo gpt -vv -r show /dev/disk0

sudo dd if=/dev/rdisk0s4 count=1 2>/dev/null | hexdump -C

3 replies
Question marked as Best reply

Jul 6, 2015 4:16 AM in response to sqd

Please ignore i386 MBR errors in the following steps. These steps correct the MBR and make MBR#4 bootable.


sudo fdisk -e /dev/disk0

p

setpid 4

07

flag 4

p

w

y


Reboot and test.


Please also the output of


diskutil list

diskutil cs list

sudo gpt -vv -r show /dev/disk0

sudo dd if=/dev/rdisk0s4 count=1 2>/dev/null | hexdump -C

How can I reinstall Boot Camp using an existing Windows partition?

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