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I have a triple boot MacBook Pro (mid-2014 model) with separate partitions for Mac OS X, Ubuntu Linux, and Windows 10 (recently upgraded, without any issues, from Windows 8.1). Before, everything booted just fine via rEFInd.

After upgrading to OS X 10.11 El Capitan, rEFInd no longer launched at startup, but I resolved that issue by reinstalling rEFInd and then running csrutil disable while in OS X recovery mode. At that point, both OS X and Ubuntu would boot up perfectly again, but when Windows (or "Legacy OS," as rEFInd calls it) was selected, the screen would turn black and say "No bootable device -- insert boot disk and press any key." If, instead of using rEFInd, I held "option" to get to the Startup Manager, only "Macintosh HD" would show up, none of the other disk partitions. The 350GB Windows partition still existed, but all attempts at booting from it or mounting it within OS X or Ubuntu failed.

Here's the message I got when attempting to mount the Windows partition in Ubuntu:

Unable to access “350 GB Volume”

Error mounting /dev/sda4 at /media/david/a56637cf-430b-3b7e-91fb-7d710c665bac:
Command-line `mount -t "hfsplus" -o "uhelper=udisks2,nodev,nosuid" "/dev/sda4"
"/media/david/a56637cf-430b-3b7e-91fb-7d710c665bac"' exited with non-zero exit
status 32: mount: wrong fs type, bad option, bad superblock on /dev/sda4,
       missing codepage or helper program, or other error
       In some cases useful info is found in syslog - try
       dmesg | tail  or so

Someone suggested I add a "boot" flag to the Windows partition, so I did so (from within Ubuntu). The Windows partition then showed up in the Startup Manager, but selecting Windows there or in the rEFInd menu still resulted in a black screen, this time with a message saying "Missing operating system." (I have since removed the "boot" flag.)

I've also attempted to fix the issue by adjusting the hybrid MBR partition table. Using rEFInd's "hybrid MBR tool" (i.e., gptsync) didn't seem to change anything, but it produced some interesting output:

Current GUID partition table:
 #     Start LBA      End LBA   Type
 1            40       409639   EFI System (FAT)
 2        409640    780652247   Unknown
 3     780652248    781921783   Mac OS X Boot
 4     781921784   1465518671   Linux Filesystem
 5    1465780816   1921269095   Linux Filesystem
 6    1921531240   1953947935   Linux Swap

Current MBR partition table:
 # A   Start LBA      End LBA   Type
 1             1    781921783   EE  EFI Protective
 2     781921784   1465518671   83  Linux
 3    1465780816   1921269095   83  Linux

Status: GPT partition of type 'Unknown' found, will not touch this disk.
Error: Not Found returned from gptsync_x64.efi

The disk slice of interest is #4, which, as you can see, is now being interpreted as a "Linux Filesystem" for some reason. That may be the root of my problem, but my research has not yet revealed enough about safely changing that sort of thing to have any confidence in doing so on my own, so please let me know what (if anything) I should do about that!

In any case, since gptsync didn't help, I manually reset the MBR via gdisk, following the same process I used when setting up my triple boot in the first place, but this didn't help either. So, again, I'm eager to hear some advice as to what I should try next.

Output from diskutil list in OS X:

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *1.0 TB     disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:          Apple_CoreStorage Macintosh HD            399.5 GB   disk0s2
   3:                 Apple_Boot Recovery HD             650.0 MB   disk0s3
   4:           Linux Filesystem                         350.0 GB   disk0s4
   5:           Linux Filesystem                         233.2 GB   disk0s5
   6:                 Linux Swap                         16.6 GB    disk0s6
/dev/disk1 (internal, virtual):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:                  Apple_HFS Macintosh HD           +399.1 GB   disk1
                                 Logical Volume on disk0s2
                                 A54F46F6-54F0-45D0-B9F9-2FE0C1D4FBF6
                                 Unencrypted

Output from diskutil info disk0s4 in OS X:

Device Identifier:        disk0s4
Device Node:              /dev/disk0s4
Whole:                    No
Part of Whole:            disk0
Device / Media Name:      Windows
Volume Name:              Not applicable (no file system)
Mounted:                  Not applicable (no file system)
File System:              None
Partition Type:           Linux Filesystem
OS Can Be Installed:      No
Media Type:               Generic
Protocol:                 PCI
SMART Status:             Verified
Disk / Partition UUID:    7BD81426-D768-45F7-BD2E-5ED6CAC0BAF5
Total Size:               350.0 GB (350001606656 Bytes)
                          (exactly 683596888 512-Byte-Units)
Volume Free Space:        Not applicable (no file system)
Device Block Size:        512 Bytes
Read-Only Media:          No
Read-Only Volume:         Not applicable (no file system)
Device Location:          Internal
Removable Media:          No
Solid State:              Yes

Output from sudo gpt -vv -r show /dev/disk0 in OS X:

gpt show: /dev/disk0: mediasize=1000555581440; sectorsize=512; blocks=1954210120
gpt show: /dev/disk0: Suspicious MBR at sector 0
gpt show: /dev/disk0: Pri GPT at sector 1
gpt show: /dev/disk0: Sec GPT at sector 1954210119
       start        size  index  contents
           0           1         MBR
           1           1         Pri GPT header
           2          32         Pri GPT table
          34           6         
          40      409600      1  GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
      409640   780242608      2  GPT part - 53746F72-6167-11AA-AA11-00306543ECAC
   780652248     1269536      3  GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
   781921784   683596888      4  GPT part - 0FC63DAF-8483-4772-8E79-3D69D8477DE4
  1465518672      262144         
  1465780816   455488280      5  GPT part - 0FC63DAF-8483-4772-8E79-3D69D8477DE4
  1921269096      262144         
  1921531240    32416696      6  GPT part - 0657FD6D-A4AB-43C4-84E5-0933C84B4F4F
  1953947936      262151         
  1954210087          32         Sec GPT table
  1954210119           1         Sec GPT header

Output from sudo fdisk /dev/disk0 in OS X:

Disk: /dev/disk0    geometry: 121643/255/63 [1954210120 sectors]
Signature: 0xAA55
         Starting       Ending
 #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
------------------------------------------------------------------------
 1: EE    0   0   2 - 1023 254  63 [         1 -  781921783] <Unknown ID>
 2: 83 1023 254  63 - 1023 254  63 [ 781921784 -  683596888] Linux files*
 3: 83 1023 254  63 - 1023 254  63 [1465780816 -  455488280] Linux files*
 4: 00    0   0   0 -    0   0   0 [         0 -          0] unused

In Ubuntu, here's the output I get from sudo parted -l:

Model: ATA APPLE SSD SM1024 (scsi)
Disk /dev/sda: 1001GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt
Number  Start   End     Size    File system     Name                  Flags
 1      20.5kB  210MB   210MB   fat32           EFI System Partition  boot
 2      210MB   400GB   399GB   hfs+            Macintosh HD
 3      400GB   400GB   650MB   hfs+            Recovery HD
 4      400GB   750GB   350GB                   Windows
 5      750GB   984GB   233GB   ext4            Linux 1
 6      984GB   1000GB  16.6GB  linux-swap(v1)  Linux 2

And finally, here's the output from lsblk in Ubuntu:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 931.9G  0 disk 
├─sda1   8:1    0   200M  0 part 
├─sda2   8:2    0   372G  0 part 
├─sda3   8:3    0 619.9M  0 part 
├─sda4   8:4    0   326G  0 part 
├─sda5   8:5    0 217.2G  0 part /
└─sda6   8:6    0  15.5G  0 part [SWAP]

I hope all that information proves useful. I should also mention I've tried booting from a Windows USB to see if that could help me do some repair work, but to no avail. Also, rEFInd does not give me the option to attempt to boot the Windows partition in recovery mode.

If I have to reformat the partition and reinstall Windows, I can accept that, but I'm hoping there's still a way to recover the partition instead. Any assistance will be greatly appreciated!

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protected by Community Nov 24 '15 at 18:25

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