"Missing Operating system_ " After installing Yosemite

I suggest a erase/restore from a good pre-Yosemite backup. I suggest putting Yosemite on the back-burner.

Do you have backup before the Yosemite upgrade?

You need to use Internet Recovery (Command+Opt+R) and start from a clean install of OS. Since you updated via App Store, you may get Yosemite back when you re-install.

Do not use a Restore the full TM backup, but use the Migration Assistant and pick what you want restored.

Please see OS X Mavericks: Transfer your info from a computer or disk.

Loner T

I am having similar issue with Windows disk error. I have rebuilt the hybrid GTP after yosemite upgrade

Any help would be greatly appreciated. I have downloaded testdisk but not sure how to proceed

Thanks so much!

Please start a new thread and post a reference back here. Your NTFS header being intact is good, but missing GPT#1 is a bit surprising. 34-409606 rather than 40-40960 is puzzling.

Please post the output of sudo fdisk /dev/disk0 in the new thread as well.

Ok thanks. I started a new thread with the additional info but how do I reference to this one

https://discussions.apple.com/thread/6613246

I just tried to install Boot Camp on a MAC running Yosemite. I installed it as a test to see if I could get it running with Windows 7. I was able to install it fine but then received the same error message shown in this post, "Missing Operating System -- No Boot device ...". I was able to fix it by inserting my Yosemite boot USB drive. I then pressed the Alt key so that I could see the boot device menu. I selected the USB drive as if to install Yosemite but went into Disk Utility. I ran a "Verify Disk" on the Mac Hard Drive (Not the Boot Camp Drive) then, even though it found no errors on the drive, a "Repair Disk" on the drive.

Once I did that I inserted my Boot Camp USB drive, pressed the ALT button and powered on the MAC. When I did this I once again saw the MAC Hard Drive and the Windows Hard drive option. I selected Windows and the installation of Windows continued. All said and done my MAC booted into Windows without failure, I then rebooted selecting the ALT option and selected the MAC Hard Drive, went into System Preferences - Startup and selected the MAC drive so that it always boots to MAC first. I hope this helps anyone who has a similar issue.

Usually a Verify (and Repair) is recommended before a BC/Windows installation. Excellent tip, thanks.

I also lost windows when I upgraded to Yosemite

Can you help me please? 😟

TestDisk 7.0-WIP, Data Recovery Utility, October 2014

Christophe GRENIER <grenier@cgsecurity.org>

http://www.cgsecurity.org

Disk /dev/disk0 - 1000 GB / 931 GiB - 1953525168 sectors (RO)

Current partition structure:

Partition Start End Size in sectors

1 P EFI System 40 409639 409600 [EFI System Partitio

2 P Mac HFS 409640 879935663 879526024 [Customer]

3 P Mac Boot 879935664 881205199 1269536 [Recovery HD]

Warning: number of heads/cylinder mismatches 255 (NTFS) != 1 (HD)

Warning: number of sectors per track mismatches 63 (NTFS) != 1 (HD)

4 P MS Data 1366915072 1953523711 586608640 [BOOTCAMP]

>[Quick Search] [ Backup ]

Try to locate partition

TestDisk 7.0-WIP, Data Recovery Utility, October 2014

Christophe GRENIER <grenier@cgsecurity.org>

http://www.cgsecurity.org

Disk /dev/disk0 - 1000 GB / 931 GiB - 1953525168 sectors (RO)

The harddisk (1000 GB / 931 GiB) seems too small! (< 1300 GB / 1211 GiB)

Check the harddisk size: HD jumpers settings, BIOS detection...

The following partitions can't be recovered:

Partition Start End Size in sectors

> MS Data 1953523711 2540132350 586608640

Mac HFS 1953525124 1954794659 1269536

[ Continue ]

NTFS, blocksize=4096, 300 GB / 279 GiB

TestDisk 7.0-WIP, Data Recovery Utility, October 2014

Christophe GRENIER <grenier@cgsecurity.org>

http://www.cgsecurity.org

Disk /dev/disk0 - 1000 GB / 931 GiB - 1953525168 sectors (RO)

Partition Start End Size in sectors

>P EFI System 40 409639 409600 [EFI]

P Mac HFS 409640 879935663 879526024

P Mac HFS 879935664 881205199 1269536

D MS Data 881205248 1953523704 1072318457

D MS Data 1366915072 1953523711 586608640

D Mac HFS 1952255592 1953525127 1269536

Structure: Ok. Use Up/Down Arrow keys to select partition.

Use Left/Right Arrow keys to CHANGE partition characteristics:

P=Primary D=Deleted

Keys A: add partition, L: load backup, T: change type, P: list files,

Enter: to continue

FAT32, blocksize=512, 209 MB / 200 MiB