Windows cant boot after windows updata

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sheilacat Author

Level 1

8 points

Windows cant boot after windows updata

my imac is 4k 27" i got my windows and mac os cant boot after windows update

I also cant see the mac os is available....

what can i do to keep my mac os back ?

Posted on Mar 17, 2018 4:12 AM

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Answer 1

Best reply

Loner T

Level 9

59,471 points

Mar 20, 2018 8:48 PM in response to sheilacat

Your Windows installation is a BIOS installation, and the MBR is missing. Can you use the Rebuild MBR section of Re: El Capitan has deleted my bootcamp windows partition and rebuild the MBR using GPT FDisk? You do not need to rebuild GPT4 again.

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Answer 2

Loner T

Level 9

59,471 points

Mar 17, 2018 9:45 AM in response to sheilacat

If you are booted into Internet Recovery, click on Utilities -> Terminal, and run

diskutil list

gpt -vv -r show /dev/disk0

Select and Copy (Command+C) the output of the Terminal sessions, quit Terminal, start Safari (Get Help Online) and Paste (Command+V) the output as a reply to this discussion.

Based on the screen shots you have posted, you may have accidentally formatted the whole disk, not just the Bootcamp partition, "Windows_LDM" is incorrect. Also, see Bootcamp panic as a reference, which has a similar issue.

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Answer 3

Loner T

Level 9

59,471 points

Mar 17, 2018 11:07 AM in response to sheilacat

Can you install macOS on an external disk using How to install OS X on an external drive connected to your Mac - Apple Support and then install GPT Fdisk (https://sourceforge.net/projects/gptfdisk/) on this external disk?

Install/upgrade to match the macOS version on the external disk, which matches what you had on the internal disk. GPT Fdisk is capable of finding the original GPT from the backup GPT, which will allow us to fix it.

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Answer 4

Loner T

Level 9

59,471 points

Mar 18, 2018 6:44 AM in response to sheilacat

Is the macOS version on the internal disk also Yosemite (10.10.x)? If yes, run

sudo gdisk /dev/disk0

I will assume that disk0 is pointing to your internal disk, but verify using diskutil list output.

The 'Bad CRC' error will force GDisk to read the backup GPT. The gpt command does not read it, even though diskutil list does. the gpt command does have a 'recover' option, but GDisk is interactive. It should prompt you for MBR or GPT, where you will need to choose GPT (2).

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Answer 5

sheilacat Author

Level 1

8 points

Mar 18, 2018 7:34 AM in response to Loner T

GPT fdisk (gdisk) version 1.0.3

Caution: invalid backup GPT header, but valid main header; regenerating

backup header from main header.

Caution! After loading partitions, the CRC doesn't check out!

Warning! Main and backup partition tables differ! Use the 'c' and 'e' options

on the recovery & transformation menu to examine the two tables.

Warning! One or more CRCs don't match. You should repair the disk!

Partition table scan:

MBR: MBR only

BSD: not present

APM: not present

GPT: damaged

Found valid MBR and corrupt GPT. Which do you want to use? (Using the

GPT MAY permit recovery of GPT data.)

1 - MBR

2 - GPT

3 - Create blank GPT

Your answer: 2

Warning! Main partition table overlaps the first partition by 34 blocks!

You will need to delete this partition or resize it in another utility.

Warning! Secondary partition table overlaps the last partition by

4613656342774127778 blocks!

You will need to delete this partition or resize it in another utility.

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Answer 6

Loner T

Level 9

59,471 points

Mar 18, 2018 7:41 AM in response to sheilacat

sheilacat wrote:

GPT fdisk (gdisk) version 1.0.3

Caution: invalid backup GPT header, but valid main header; regenerating

backup header from main header.

Caution! After loading partitions, the CRC doesn't check out!

Warning! Main and backup partition tables differ! Use the 'c' and 'e' options

on the recovery & transformation menu to examine the two tables.

Yes, this is expected. Please post the output of 'p' (print) command. Good to see GDisk is able to correctly find information.

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Answer 7

sheilacat Author

Level 1

8 points

Mar 18, 2018 8:05 AM in response to Loner T

Disk /dev/disk0: 490234752 sectors, 233.8 GiB

Sector size (logical): 512 bytes

Disk identifier (GUID): 207BCAF1-2DC8-41D2-8D1A-773AEAEA4392

Partition table holds up to 128 entries

Main partition table begins at sector 2 and ends at sector 33

First usable sector is 34, last usable sector is 490234718

Partitions will be aligned on 8-sector boundaries

Total free space is 1373 sectors (686.5 KiB)

Number Start (sector) End (sector) Size Code Name

1 40 409639 200.0 MiB EF00 EFI System Partition

2 409640 235058919 111.9 GiB AF05 Customer

3 235058920 236328455 619.9 MiB AB00 Recovery HD

4 236328960 490233855 121.1 GiB 0700 BOOTCAMP

17 18376656804508598272 4613656343264362496 512 bytes FFFF

19 2089670227099975680 2089670227108256568 3.9 GiB FFFF

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Answer 8

Loner T

Level 9

59,471 points

Mar 18, 2018 8:19 AM in response to sheilacat

We will rebuild the GPT first. (Do not enter text like this. It is informational).

Step A - Creates a blank GPT. Choose 2 for GPT, if prompted.

sudo gdisk /dev/rdisk0

o (Create a new GPT)

p (print)

w (write)

y (confirm write)

q (quit, if necessary)

Step B. Create individual entries .

sudo gdisk /dev/rdisk0

x (Experts menu)

l (Set alignment. This is is lower case L )

1 (to one sector. This is digit 1 )

m (Go to main menu)

n (New)

1 (GPT1)

40 (Start)

409639 (End)

EF00 (EFI)

n (New)

2 (GPT2)

409640

235058919

AF05 (CoreStorage)

n (New)

3 (GPT3)

235058920

236328455

AB00 (Recovery HD)

n

4

236328960

490233855

0700 (Microsoft Basic Data)

p (Print)

w (write)

y (confirm write)

Step C. Repair disk .

diskutil repairDisk disk0

Reboot and hold Alt/Option key. Do you see macOS on the internal disk as a selection? If yes, select it and test booting.

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Answer 9

sheilacat Author

Level 1

8 points

Mar 18, 2018 8:46 AM in response to Loner T

Should i proceed ? (Repairing the partition map might erase disk0s1)

Command (? for help): p

Disk /dev/rdisk0: 490234752 sectors, 233.8 GiB

Sector size (logical): 512 bytes

Disk identifier (GUID): 489D8FC1-47FE-48BE-B827-A13C68A87126

Partition table holds up to 128 entries

Main partition table begins at sector 2 and ends at sector 33

First usable sector is 34, last usable sector is 490234718

Partitions will be aligned on 1-sector boundaries

Total free space is 1373 sectors (686.5 KiB)

Number Start (sector) End (sector) Size Code Name

1 40 409639 200.0 MiB EF00 EFI System

2 409640 235058919 111.9 GiB AF05 Apple Core Storage

3 235058920 236328455 619.9 MiB AB00 Recovery HD

4 236328960 490233855 121.1 GiB 0700 Microsoft basic data

Command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING

PARTITIONS!!

Do you want to proceed? (Y/N): y

OK; writing new GUID partition table (GPT) to /dev/rdisk0.

Warning: The kernel may continue to use old or deleted partitions.

You should reboot or remove the drive.

The operation has completed successfully.

karys-iMac:~ kary$ diskutil repairDisk disk0

Repairing the partition map might erase disk0s1, proceed? (y/N)

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Answer 10

Loner T

Level 9

59,471 points

Mar 18, 2018 10:50 AM in response to sheilacat

sheilacat wrote:

oh i get my mac os back !!! Thank you so much!!!!!

Cool.

sheilacat wrote:

but windows wasnt ..... do you think is it possible to bring my windows back ?

What is the year of your iMac - 2014 or something different?

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Answer 11

sheilacat Author

Level 1

8 points

Mar 24, 2018 6:17 AM in response to Loner T

windows was back too !!!!!! i was so happy the both os were back.

before the windows back, i need to boot windows at safe mode first(normal boot fail). Then the windows rollback the update , and the windows back.

very appreciate what you do for me. You are my savior!!

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Answer 12

sheilacat Author

Level 1

8 points

Mar 17, 2018 10:53 AM in response to Loner T

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Answer 13

sheilacat Author

Level 1

8 points

Mar 17, 2018 11:52 PM in response to Loner T

ok i buy one and try it

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Answer 14

sheilacat Author

Level 1

8 points

Mar 18, 2018 2:17 AM in response to Loner T

i have 10.10.5 and i installed gptfdisk how can i find the backup GPT ?

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Answer 15

Loner T

Level 9

59,471 points

Mar 18, 2018 9:59 AM in response to sheilacat

Yes, please continue. Disk Utility will rebuild EFI, if necessary.

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Windows cant boot after windows updata

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