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Missing operating system after MBR repair

Hi,


I have dual system on my mac book pro, windows on boot camp. I haven't been using windows for a while and when I tried to log back in recently, I found that I can't see windows after pressing 'alt' upon start up. I then searched here and found a solution to the problemRepairing boot camp after OS install 10.10.2. After the repair, I can now see windows during start up, but when I tried to boot into it, it displays 'missing operating system...'. I then found another possible solution to the problem, which told me to try to use the startup repair option on windows disk to fix the problem. It did not work. Hope I can get some help on here. Thanks.


@Kappy


Yang

Posted on Feb 24, 2015 1:06 PM

Reply
34 replies

Feb 24, 2015 2:48 PM in response to aurthes

aurthes wrote:


entry 2 is my macintosh partition, which is working properly now. what's the effect of that incorrect id?

The MBR may confuse others. You can correct by syncing the MBR with the GPT using Gdisk 'r' and 'h' options.


There is no NTFS header, which is why you are unable to boot into Windows. Did you recently upgrade to Yosemite from older OS X version with BC/Windows in place? Was there any recent resizing/repartitioning of Windows or OS X using Disk Utility?

Feb 24, 2015 5:36 PM in response to aurthes

Has there been any resizing/repartitioning activity after Windows installation on any version of OS X?


Please also see Bootcamp partition has disappeared after upgrade to Yosemite 10.10 and download Testdisk and GPT Fdisk and start with a Testdisk scan. The puzzling part is that the gap between GPT3/4 is fairly small. The other variants that I have seen are no gaps at all.

Feb 24, 2015 8:18 PM in response to Loner T

1. can you walk me through how to sync MBR with GPT?


2. I do not remember doing any resizing/repartitioning activity after Windows installation on any version of OS X.


3. I am running a scan(quick search) now. Here's what I have now


User uploaded file


Two 4s, I think that a problem. Btw, when I started, I encountered this message:


User uploaded file


and I chose continue. I hope this won't be a problem.


4. By gap between GPT 3/4 do you mean:


User uploaded file


293511295 - 293513216? I should be smaller like 1? What does a gap imply?

Feb 25, 2015 4:07 AM in response to aurthes

aurthes wrote:


1. can you walk me through how to sync MBR with GPT?

In the article that you reference in the OP, the steps using the Recovery and Hybrid menu is what I was referring to. Gdisk overwrites the existing MBR when the steps are executed. You have successfully done it, at least once. You may have chosen 0x'AF00' rather than 0x'AF05' based on an example. It does not create issues, but the output of commands looks out of sync. It can be left alone, because you may need to recreate after the Testdisk run anyway.


2. I do not remember doing any resizing/repartitioning activity after Windows installation on any version of OS X.

Yosemite upgrades do not take kindly to NTFS headers being moved around. The upgrade seems to pick the incorrect NTFS entry in cases where some tool was used to resize the Windows side. It manifests itself when there 'gap' between GPT 3 and GPT 4 is roughly the same size as the resizing attempt was. In your specific case there is a much smaller 1920 sector gap, which does not indicate any attempts, but just an alignment on the disk at sector boundaries.



3. I am running a scan(quick search) now. Here's what I have now

The two MS Data entries with same size/start indicate a partition history of sorts. Continue with Quick Search, but more than likely, you will need Deeper Search.



Two 4s, I think that a problem. Btw, when I started, I encountered this message:


User uploaded file


and I chose continue. I hope this won't be a problem.


4. By gap between GPT 3/4 do you mean:


User uploaded file


293511295 - 293513216? I should be smaller like 1? What does a gap imply?

Because you are booted from the same disk you are scanning with Testdisk, it is warning that it cannot modify the disk of partition changes. On Macs, Testdisk is primarily used to scan, and all changes are made using Gdisk/GPT commands. The reference to a 'gap' is the number of sectors between GPT3 and GPT4. The link in the OP references a disk which has no gaps, but the Hybrid MBR was incorrect. If you look at the second link I provided, which has the Testdisk scanning, OP's GPT output shows gaps.

Feb 25, 2015 7:04 AM in response to aurthes

Did you use EFI/GPT when Testdisk was started?


There is line above which says 'The following partitions can't be recovered'. The end column for the first three entries has values which are beyond the physical limits of your specific HD, and cannot be recovered.

The MS Data is no longer valid, because it was relocated.

The last entry is your Recovery HD, which was also relocated.

These entries indicate 'stale' information, or corrupted information. Press Enter to Continue.

Please see http://imgur.com/a/PjmnK for the Testdisk starting screens and flow.

Missing operating system after MBR repair

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