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I am trying to install Windows 8 on an iMac (mid 2010 model). The iMac already has Ubuntu 14.04 installed on it which I intend to keep. So basically I would like to dual boot Ubuntu and Windows 8. (There is no OSX on this machine).

My internal HDD has the following setup:

  • EFI boot partition
  • Ext4 partition for Ubuntu
  • NTFS partition (empty currently) for Windows 8
  • SWAP partition

I booted the Windows 8 installation USB and clicked through the Windows 8 installer until I got to the partitioning section.

After selecting the partition on which I want to install Windows 8 (NTFS partition), the installer throws the following error which is German so I have attempted to translate it:

Your EFI partition is not in NTFS format. Try formatting the EFI partition to FAT32

I am sure my EFI partition is in FAT format, but perhaps it is in FAT16 (I originally used the Ubuntu Live CD installer to install Ubuntu on this machine and it created the EFI boot partition so I am not sure what is chosen as standard).

So my question is what is the best things to do now in order to be able to install Windows 8?

If I change the format of the EFI boot partition then obviously that is going to destry any data on it and then I will not be able to boot into Ubuntu.

Is there any way to save the contents of the boot partition, then format it and then copy back the contents?

Or is there a simpler method? Perhaps format the boot partition and then use Boot Repair? Would that work? Or will formatting it delete crucial data that cannot even be restored/fixed using Boot Repair?

Update 1:

Gparted says that /dev/sda1 is fat32 with the boot flag.

The output of gdisk -l /dev/sda1 is:

GPT fdisk (gdisk) version 0.8.8

Partition table scan:
  MBR: MBR only
  BSD: not present
  APM: not present
  GPT: not present


***************************************************************
Found invalid GPT and valid MBR; converting MBR to GPT format
in memory. 
***************************************************************

Disk /dev/sda1: 1048576 sectors, 512.0 MiB
Logical sector size: 512 bytes
Disk identifier (GUID): D3ADE546-714D-4E91-B07D-8BB7AF42128D
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 1048542
Partitions will be aligned on 2048-sector boundaries
Total free space is 1048509 sectors (512.0 MiB)

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

The output of sudo parted /dev/sda print is:

Model: ATA WDC WD1003FZEX-0 (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/4096B
Partition Table: gpt

Number  Start   End     Size    File system     Name  Flags
 1      1049kB  538MB   537MB   fat32                 boot
 2      538MB   567GB   566GB   ext4
 9      987GB   1000GB  12,9GB  linux-swap(v1)
2

You reported the following error message:

Your EFI partition is not in NTFS format. Try formatting the EFI partition to FAT32

This is confusing, since it seems to imply that the Windows installer wants the partition be both NTFS and FAT32 -- an impossibility. In fact, the EFI System Partition (ESP) must be FAT, and Windows wants it to be FAT32. (The EFI spec mentions FAT32 explicitly but also mentions other FAT bit depths elsewhere, so the spec could be clearer.) I suspect the reference to NTFS is either a typo on your part or a bug in the Windows installer, and will proceed under that assumption....

I am sure my EFI partition is in FAT format, but perhaps it is in FAT16 (I originally used the Ubuntu Live CD installer to install Ubuntu on this machine and it created the EFI boot partition so I am not sure what is chosen as standard).

Ubuntu's installer will use FAT for the ESP, but which bit depth depends on the partition's size -- or at least, that was the case a few versions ago. You can check the current FAT type by using parted or GParted, as in:

$ sudo parted /dev/sda print
Model: ATA Samsung SSD 850 (scsi)
Disk /dev/sda: 250GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start   End     Size    File system  Name                 Flags
 1      524kB   1573kB  1049kB               BIOS boot partition  bios_grub
 2      1573kB  580MB   579MB   fat32        EFI System           boot
 3      580MB   1106MB  525MB   ext4         Xubuntu /boot
 4      1106MB  1631MB  525MB   ext4         Ubuntu /boot         legacy_boot
 5      1631MB  250GB   248GB                Linux LVM            lvm

As you can see, this disk's ESP (/dev/sda2) is FAT32.

If you find that your ESP is FAT16, then yes, you can back it up, create a fresh FAT32 filesystem on it, and restore it -- at least, assuming it's big enough to hold a FAT32 filesystem (IIRC, the minimum size for a FAT32 filesystem is 32MiB). Note that you'll almost certainly need to update your /etc/fstab entry for the new serial number (incorrectly called a "UUID" by most Linux utilities and configuration files, including /etc/fstab). Alternatively, you can check the current serial number (as retrieved from /etc/fstab or detected by blkid) and then pass that as a value to the -i option to mkdosfs to re-use the old number.

  • Thanks very much for the great feedback. How would I go about seeing the content that is on the boot partition? Is there a way to mount that partition safely? – PartisanEntity Aug 3 '15 at 13:42
  • Oh sorry, ignore my comment. the contents of my efi boot partition should be in /boot/efi right ? – PartisanEntity Aug 3 '15 at 14:26
  • In Ubuntu and assuming a standard installation, then yes, the ESP will be at /boot/efi. You can use df to view where all your partitions are mounted and parted or gdisk to view the partition table. It should be possible to piece it all together from this information even if your installation deviates from the standard. – Rod Smith Aug 3 '15 at 16:53
  • Do I need to be booted from a live USB to format the boot partition? Or can I do it booted normally? – PartisanEntity Aug 3 '15 at 19:45
  • I have updated my question with more info from various command output. If am reading the data right, /dev/sda1 is already in fat32 as the windows 8 installer requested. Strange. – PartisanEntity Aug 3 '15 at 21:16

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