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Tobia
Asked: 2017-02-02 14:56:28 +0800 CST

Weird partitioning issue on MacBook Air

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I have a working triple-boot system on a MacBook Air (Mac OS X + Windows 7 + Ubuntu) that I achieved some time ago by following various tutorials.

Now I'd like to spice it up a bit by reinstalling Ubuntu with full disk encryption (using this great tutorial) and removing Mac OS X entirely, since I never use it anymore.

But I'm hitting a roadblock: as soon as I touch the GPT, no matter how little I change, Windows becomes unbootable!

Here is the current, working partition table (Linux gdisk command p)

Disk /dev/sda: 490234752 sectors, 233.8 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): DC542B27-E782-479A-B17F-AAB05FACFA6C
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 490234718
Partitions will be aligned on 8-sector boundaries
Total free space is 2877 sectors (1.4 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1              40          409639   200.0 MiB   EF00  EFI System Partition
   2          411648       160409599   76.3 GiB    8300  
   3       160409600       168409087   3.8 GiB     8200  
   4       168409088       244826335   36.4 GiB    AF00  Apple_HFS_Untitled_2
   5       244826336       246095871   619.9 MiB   AB00  Recovery HD
   6       246095872       490233855   116.4 GiB   0700  BOOTCAMP

Partitions 2 and 3 are Linux root and swap respectively.

This is the protective MBR (command: r o)

Disk size is 490234752 sectors (233.8 GiB)
MBR disk identifier: 0x4B9CA30C
MBR partitions:

Number  Boot  Start Sector   End Sector   Status      Code
   1                     1    246095871   primary     0xEE
   2      *      246095872    490233855   primary     0x07

What I'd like to do is to remove GPT partitions 2 to 4 (not to be confused with MBR partition 2 above), replacing them with a 256MB Linux boot and a LUKS partition holding everything else. (I'll keep the Mac OS X recovery just in case I need some utility to write to nvram or something.)

I can easily do it with commands: d 2, d 3, d 4, n 2 default +256M, n 3 default default. The result is thus:

...
Total free space is 869 sectors (434.5 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1              40          409639   200.0 MiB   EF00  EFI System Partition
   2          409640          933927   256.0 MiB   8300  Linux filesystem
   3          933928       244826335   116.3 GiB   8300  Linux filesystem
   5       244826336       246095871   619.9 MiB   AB00  Recovery HD
   6       246095872       490233855   116.4 GiB   0700  BOOTCAMP

Printing the protective MBR shows the exact same table as before.

And yet, if I write this to disk and reboot, Windows won't boot anymore! even though I haven't changed its partition, nor the protective MBR.

If I hold Alt during boot and choose Windows, I get a weird sequence of screens that end in a Grub command prompt! Where is that Grub coming from, is a mystery.

Luckily I had a foreboding that something like this might happen, so I made a complete Clonezilla backup before touching anything. Now I can easily restore the system to the working triple boot state and try again. But no matter what I try, I break it!

How can I modify these partitions without borking Windows?

Edit—here are the weird Grub screens when I try to boot Windows after changing the GPT:

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In the second screen it mentions 3 partitions of type 0xEE. Where are they coming from? Where is this Grub coming from in the first place??

dual-boot

0 Answers