FAT32 partition not visible in Windows on Triple-Boot System

Discussion in 'Windows, Linux & Others on the Mac' started by s1lent.ey3s, Nov 1, 2009.

  1. s1lent.ey3s macrumors newbie

    Jul 28, 2008
    I set up a triple-boot system on my MBP (Early 2008) with OS X SL, ubuntu 9.10 and Windows 7 Home Premium. I have a 500GB Hard Drive, and allocated 100 GB for Mac OS X, 60 GB for Windows 7, 40 GB for ubuntu, and the remainder I formatted as FAT32 for storage to share between the three operating systems (to hold iTunes and iPhoto libraries, movies, etc).

    I use rEFIt as my bootloader, and all three operating systems happily load whenever I choose them to. The problem lies with the FAT32 storage partition. OS X recognizes it quite nicely and I use it regularly. Windows and ubuntu, however, do not mount it. What's more, Windows Disk Manager identifies the space as unallocated space. Does anybody have any suggestions as to how to address this?

    Also, I backed up the data on the storage volume and tried formatting it as NTFS and HFS+, and they still won't properly show. I use MacDrive 8 on the Windows side for access to Mac partitions.
  2. s1lent.ey3s thread starter macrumors newbie

    Jul 28, 2008
  3. Infrared macrumors 68000


    Mar 28, 2007
    Could you run 'fdisk' from the OS X terminal so we can see
    how the MBR partition table looks?

  4. Bill Gates macrumors 68020

    Bill Gates

    Jun 21, 2006
    Run "gptsync" from rEFIt. My guess is that the gpt and MBR partitioning schemes are out of sync.
  5. Infrared macrumors 68000


    Mar 28, 2007
    Other thing is he probably has 5 partitions: Hidden EFI, OS X, Ubuntu,
    Win7, FAT32. That could be an issue given that only 4 primary partitions
    are permissible. I'd like to see what's in that partition table :)
  6. gugucom macrumors 68020


    May 21, 2009
    Munich, Germany
    I bet that is the core of the issue. The use of FAT32 is also not recommended because any file above 4 GB would stall the use of the partition.
  7. s1lent.ey3s thread starter macrumors newbie

    Jul 28, 2008
    I ran fdisk from the Mac Terminal. I wasn't sure exactly what you wanted, but the command I used was sudo fdisk /dev/rdisk0, but I'm not entirely familiar with the tool, so I could have used the wrong command entirely.

    The output was:
    Disk: /dev/rdisk0	geometry: 60801/255/63 [976773168 sectors]
    Signature: 0xAA55
             Starting       Ending
     #: id  cyl  hd sec -  cyl  hd sec [     start -       size]
     1: EE 1023 254  63 - 1023 254  63 [         1 -     409639] <Unknown ID>
     2: AF 1023 254  63 - 1023 254  63 [    409640 -  200080144] HFS+        
    *3: 07 1023 254  63 - 1023 254  63 [ 200751928 -  117472232] HPFS/QNX/AUX
     4: 83 1023 254  63 - 1023 254  63 [ 318486528 -   86489088] Linux files*
    Running gptsync from rEFIt yielded:
    Current GPT partition table:
    #	 Start LBA	End LBA		Type
    1	40	 	409639		EFI System (FAT)
    2	409640		200489783	Mac OS X HFS+
    3	200751928	318224159	Basic Data
    4	318486528	404975615	Basic Data
    5	404975616	408377959	Linux Swap
    6	408379392	976510983	Mac OS X HFS+
    Current MBR Partition Table
    # A	Start LBA	End LBA		Type
    1	1		409639		EE EFI Protective
    2	409640		200489783	AF Mac OS X HFS+
    3 *	200751928	318224159	07 NFTS/HPFS
    4	318486528	404975615	83 Linux
    Status: Tables are synchronized, no need to sync.
    It should be noted that I reformatted the storage partition yet again to HFS+, particularly because of the 4GB file size limit. And "Basic Data" 3 is Windows, 4 is Linux.

    In regards to the 4 primary partition limit, is there any way around that? Could I, perhaps, install Linux instead to an extended partition, which would house the Linux boot and swap partitions, as well as the Storage partition? I'm not sure if Linux can boot off extended partitions...

    Also, I don't mind at all reinstalling everything. I always have everything backed up, so all it would take for me is time.
  8. Infrared macrumors 68000


    Mar 28, 2007
    Ok, that's great. As you can see, the MBR entries are seemingly correct,
    but your storage partition isn't one of them. I would guess the entry wasn't
    added to the MBR partition table due to the 4 partition limit.

    OS X relies upon the GUID partition table which isn't limited to 4 entries and
    your storage partition is partition 6 in that table. That explains why the
    partition is visible to OS X, but not to operating systems relying upon the
    MBR partition table.

    I think there probably is, but I'm not entirely certain.
  9. s1lent.ey3s thread starter macrumors newbie

    Jul 28, 2008

    Well, I figure I might as well ask first to possibly save myself the time reinstalling stuff... I would get by without accessing the storage partition from Linux since I don't use it very often, but I do use Mac and Windows equally and often-- I would say they're both my primary operating systems, and having the space outside a boot partition makes navigating through directory trees easier. If I moved the partitions to this configuration:
    1: EFI Protective
    2: Mac OS X
    3: Windows
    4: Storage
    5: Ubuntu
    6: Linux Swap

    I'm almost certain that Mac and Windows would be able to share the Storage partition, but would rEFIt be able to boot Ubuntu?
  10. Infrared macrumors 68000


    Mar 28, 2007
    I wonder if a more straightforward solution would be to replace the
    EFI entry in the MBR table with a reference to the storage partition.
  11. hintza macrumors newbie

    Nov 17, 2010
    Did you ever solve your problem?

    Just started looking into this, as I'm about to implement the same sort of thing. (Triple-boot Mac w/ shared data partition.) I've found lots of contradictory articles on the web. But as best I can tell, it sounds like Windows 7 might not look past the MBR when both an MBR and GPT table are present. If that's true, it would mean your shared data partition would have to be among the first four.

    I don't think you want to move Ubuntu out of the first four. I'm assuming Grub is on your Ubuntu partition, and it sounds like Grub might not work if it's on a Mac partition above 4. And you probably don't want to get rid of that first EFI partition. I'm forgetting why, but I recall hearing it was important for some reason.

    So you may have to move MacOS out of the first four, to make room for the EFI partition, Linux w/ Grub, Windows, and data. I'm not crazy about this solution. I was under the impression that earlier partitions are toward the outer rim of the drive, leading to faster seek times. So I really wanted MacOS to be my second partition, rather than my fifth. But it looks like I may have to bite the bullet and put the MacOS partition fifth. Let me know if you come up with a better solution, though.

    And please correct me if I've got anything wrong.
  12. balamw Moderator


    Staff Member

    Aug 16, 2005
    New England
    You might want to take a look at gdisk/GPT fdisk as an alternative to gptsync/fdisk while working on this. It does more than just sync the GPT and MBR partition tables.


  13. huckduck, Nov 17, 2010
    Last edited: Nov 17, 2010

    huckduck macrumors newbie

    Mar 31, 2009
    hi guys,

    i got it working after countless trial and error formats because the online information is so sketch.

    i found partitioning this way works

    Initial setup for win7/vista:
    1. HFS+ (OSX)
    2. FAT32 (Data/Storage/Shared)
    3. FAT32/NTFS (Windows 7 or Vista)
    4. FAT32 (Linux)

    this will make your MBR look like:
    1. EFI Protective
    2. HFS+
    3. FAT32
    4. FAT32

    and your gpt look like
    1. EFI Protective
    2. HFS+
    3. Microsoft Basic Data
    4. Microsoft Basic Data
    5. Microsoft Basic Data

    then install (in this order) OSX to the OSX Drive, Windows to the Windows drive, and Linux to the linux drive *with the bootloader on the data drive*


    i would also suggest NOT formatting at all in windows as it will kill your tables.

    install ntfs-3g on linux and osx to get ntfs read/write.
  14. chinarut macrumors member

    Nov 14, 2005
    installing bootloader on data partition is key!

    OMG! you really rock - this one tip alone allowed me to get my triple-boot up and running just now - i really thought I had to wipe my drive clean after 12 hrs of work and nope - this tip works! :cool:

    FYI - this is what worked for me (Mac OS X 10.6.6, WinXP, Ubuntu 10.4):

    very happy - i can go to sleep :D

    Current GPT partition table:
    #	 Start LBA	End LBA		Type
    1	40	 	409639		EFI System (FAT)
    2	409640		 274199287	Mac OS X HFS+
    3	 274371432	1128361775	Mac OS X HFS+
    4	1128624128	1206747135	Basic Data
    5	1206747136	1246746623	Basic Data
    6	1246746624	1250263039	Linux Swap
    Current MBR Partition Table
    # A	Start LBA	End LBA		Type
    1	         1	409639		EE EFI Protective
    2	    409640	274199287	AF Mac OS X HFS+
    3 	 274371432	1128361775	AF Mac OS X HFS+
    4 *	1128624128	1206747135	07 NTFS/HPFS
  15. MrAtheist macrumors newbie

    Apr 26, 2011
    sorry to bump this thread... but im in the same boat and need some help!

    so about this partition to be shared between 3 oses, how do you format it to be ntfs?

    do you do it under mac or ubuntu? and which format should be set?

    and what does it mean by setting the bootloader to the data drive? do you set it to point to the shared partition? (if i understand it correctly)
  16. chinarut macrumors member

    Nov 14, 2005
    wow - it's been so long since I've fiddled with this I hope you others can chime in too...

    if I remember correctly, I let my WinXP install do the formatting of my Windows partition.

    I did it at the commend level and I think it was from Ubuntu. as long as your partition table looks like the post above, you should be good...

    this I'm a bit foggy on as well - if I remember correctly, the "*" on sector 1128624128 denotes where the bootloader is and as you can see in the GPT partition table, it coincides with where I have my DATA (or technically - MEDIA) partition.

    I don't think i can help much beyond this so good luck!
  17. Nopstnz8 macrumors member


    Mar 22, 2010
    So does this mean Linux is outside of the MBR and 5th on the GPT?

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