Partition pain

m0ng wrote:

Sorry. Hope I'm not making you rip your hair out.

btw ever now and again I'm getting an error come up in OS X saying "the disk inserted is unreadable by os x" or something similar...

anyway:

Create a blank new GPT, and create new entries using these start/end values. You need to use the n command and maintain the sequence and code column.

Please verify all values for typos.

1. Create a new GPT.

2. x (Experts menu)

3. l (Alignment)

4. 1 (1 sector)

5. m (Main Menu)

6. n (New)

7. 1 (GPT #1)

8. 40 (Start)

9. 409639 (End)

10. EF00 (EFI)

11. n (new)

12. 2 (GPT#2)

13. 409640 (Start)

14. 702397983 (End)

15. AF00 (OSX)

16. n (New)

17. 3 (GPT#3)

18. 702397984 (Start)

19. 703667519 (End)

20. AB00 (Recovery HD)

21. n (New)

22. 4 (GPT#4)

23. 703668224 (Start)

24. 977104985 (End)

25. 0700 (NTFS)

26. p

27. w

28. y

Reboot and check OS X and Windows partitions. Try to boot from internal disk OS. Windows is not ready yet.

m0ng wrote:

I was trying to free up some space from my windows 10 partition to go back to my Mac OS X 10.10.2 partition. You used to be able to do this in either boot amp or the disk utility just by dragging the sliders, I'm sure...i couldn't get it to work in Mac I looked online and read somewhere that Windows 10 could do it natively.

This has never been supported. Please see Boot Camp: Resize the Windows partition . Snow Leopard was a bit more forgiving, but not many others.

In Windows 10 disk management o resized the bootcamp partition to free up some space. This then created an empty partition, so I headed back to OS X, but it didn't seem to see it in disk utility, aback to Windows 10, I thought if I formatted it as fat32 os X would see it and be able to reclaim the space.

Windows has no idea it is running on a Mac and overwrites the Mac EFI.

would someone please give me some advice? - will it be possible to save the data on the os X partition? (Not so bothers about Windows 10)???

Use OS X: About OS X Recovery - Apple Support and boot into Internet Recovery. Find a 16GB Flash drive, if you can, and How to install OS X on an external drive connected to your Mac - Apple Support and boot from this. Boot from this external disk, and we can inspect the internal disk for recoverability.

Try with the 8GB flash drive. If you run into any space issues, please post back.

From How to install OS X on an external drive connected to your Mac - Apple Support

Your external drive needs a GUID partition with at least 8 GB of available space to install OS X. For best results, the volume should be formatted as Mac OS X Extended format (not FAT, NTFS, or EXFAT).

1. Please use How to install OS X on an external drive connected to your Mac - Apple Support and get the OS X version shipped with your Mac.

2. Upgrade the SD Card to El Capitan from the App Store .

3. Once you have ELC on the SD Card, boot from it and install GPT Fdisk - http://sourceforge.net/projects/gptfdisk/on the SD Card.

The SD Card may have a loose connection. You need to boot into Recovery HD of the SD card by powering down and starting with Command+R or Alt/Option key. Once you are in Recovery console,

Step A - Disable El Capitan temporarily (About System Integrity Protection on your Mac - Apple Support)

1. Boot into Local Recovery (Command+R).

2. Start Utilities -> Terminal.

3. Type csrutil disable in Terminal and press Enter/Return.

4. Type csrutil status.

5. Boot normally, and type csrutil status to confirm that all individual entries are still disabled.

Once you boot normally, we can proceed further with Gdisk again.

If you look at Re: Partition pain, there is a message

Partitions will be aligned on 8-sector boundaries

If you compare https://discussions.apple.com/content/attachment/662192040 and compare it to

m0ng wrote:

here we are:

Last login: Fri Jan 1 05:12:28 on ttys000

davids-MacBook-Pro:~ m0ng$ sudo gpt -vv -r show /dev/disk0

gpt show: /dev/disk0: mediasize=500277790720; sectorsize=512; blocks=977105060

gpt show: /dev/disk0: PMBR at sector 0

gpt show: /dev/disk0: Pri GPT at sector 1

gpt show: /dev/disk0: Sec GPT at sector 977105059

start size index contents

0 1 PMBR

1 1 Pri GPT header

2 32 Pri GPT table

34 2014

2048 407592 1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B

409640 2008

411648 701986336 2 GPT part - 48465300-0000-11AA-AA11-00306543ECAC

702397984 480

702398464 1269056 3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC

703667520 704

703668224 273436672 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7

977104896 131

977105027 32 Sec GPT table

977105059 1 Sec GPT header

davids-MacBook-Pro:~ m0ng$

You can see the issue. The start/end must match exactly.

Please redo the GPT after you change the sector alignment to 1 sector as shown...

sudo gdisk /dev/disk0

Password:

GPT fdisk (gdisk) version 1.0.0

Warning: Devices opened with shared lock will not have their

partition table automatically reloaded!

NOTE: Write test failed with error number 1. It will be impossible to save

changes to this disk's partition table!

Partition table scan:

MBR: hybrid

BSD: not present

APM: not present

GPT: present

Found valid GPT with hybrid MBR; using GPT.

Command (? for help): p

Disk /dev/disk0: 500118192 sectors, 238.5 GiB

Logical sector size: 512 bytes

Disk identifier (GUID): 22749ACF-207D-458E-B255-5DF02C39DC2D

Partition table holds up to 128 entries

First usable sector is 34, last usable sector is 500118158

Partitions will be aligned on 8-sector boundaries

Total free space is 1325 sectors (662.5 KiB)

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

1 40 409639 200.0 MiB EF00 EFI System Partition

2 409640 250801735 119.4 GiB AF05 OSY-MBP13

3 250801736 252071271 619.9 MiB AB00 Recovery HD

4 252071936 500117503 118.3 GiB 0700 BOOTCAMP

Command (? for help): x

Expert command (? for help): ?

a set attributes

c change partition GUID

d display the sector alignment value

e relocate backup data structures to the end of the disk

g change disk GUID

h recompute CHS values in protective/hybrid MBR

i show detailed information on a partition

l set the sector alignment value

m return to main menu

n create a new protective MBR

o print protective MBR data

p print the partition table

q quit without saving changes

r recovery and transformation options (experts only)

s resize partition table

t transpose two partition table entries

u replicate partition table on new device

v verify disk

w write table to disk and exit

z zap (destroy) GPT data structures and exit

? print this menu

Expert command (? for help): l

Enter the sector alignment value (1-65536, default = 2048): 1

Expert command (? for help): p

Disk /dev/disk0: 500118192 sectors, 238.5 GiB

Logical sector size: 512 bytes

Disk identifier (GUID): 22749ACF-207D-458E-B255-5DF02C39DC2D

Partition table holds up to 128 entries

First usable sector is 34, last usable sector is 500118158

Partitions will be aligned on 1-sector boundaries

Total free space is 1325 sectors (662.5 KiB)

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

1 40 409639 200.0 MiB EF00 EFI System Partition

2 409640 250801735 119.4 GiB AF05 OSY-MBP13

3 250801736 252071271 619.9 MiB AB00 Recovery HD

4 252071936 500117503 118.3 GiB 0700 BOOTCAMP

Expert command (? for help):

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. Please see the sample Q&A before you execute these steps.

1. Sudo gdisk /dev/rdisk0
2. P (Print list of parts)
3. R (Recover)
4. O (print current Hybrid MBR)
5. H (chooses Hybrid)
6. Partitions numbers to be hybridized: 2 3 4
7. Y (Good for GRUB question)
8. N (part 2 boot flag)
9. N (part 3 boot flag)
10. Y (part 4 boot flag make NTFS bootable partition)
11. O (print current Hybrid MBR)
12. W (Write the new MBR)
13. Y (Yes! write the new MBR)
14. Reboot

Here is sample Q&A for this section. Please notice the Press Enter/Return.

Place EFI GPT (0xEE) partition first in MBR (good for GRUB)? (Y/N): Y

Creating entry for GPT partition #2 (MBR partition #2)

Enter an MBR hex code (default AF): Press Enter/Return

Set the bootable flag? (Y/N): N

Creating entry for GPT partition #3 (MBR partition #3)

Enter an MBR hex code (default AB): Press Enter/Return

Set the bootable flag? (Y/N): N

Creating entry for GPT partition #4 (MBR partition #4)

Enter an MBR hex code (default 07): Press Enter/Return

Set the bootable flag? (Y/N): Y

Test 1 - Does Bootcamp Volume show up in Finder? (This works)

Test 2 - Can you see files in Bootcamp Volume? (This works)

Test 3 - Can you select Bootcamp in System Preferences -> Startup Disk?

Test 4 - If Test 3 is successful, select Bootcamp and Click Restart.

If all looks normal, please back up OS X, Windows and create Windows System Restore point.

Your Mac originally shipped with Mountain Lion, which is why you were offered ML. Since you were on El Capitan before the problem started, can you upgrade the external USB to El Capitan, if possible, before we proceed further? There are significant differences between ML (10.8) and ELC (10.11) and it would better to avoid issues resulting from such differences.

Your disk, unless modified further, should be salvageable. In most cases, changing Partition GUIDs will allow the disk to work. This is the reason to put ELC on an external disk, with GPT Fdisk, so the GPT entries on the internal disk can be corrected.