Install Windows 10 with larger EFI partition

Question

Is there a way to do a fresh install of Windows 10 on an empty drive with a larger EFI partition than 100MB (approx 200MB)? I plan to dual boot OS X and I want to avoid a certain issue that might pop up.

Answer 1

In order to custom size any non-data partition [EFI, WinRE], the drive must be manually partitioned via DiskPart prior to installing Windows.

• If this needs to be done more than once, it may be more efficient time-wise to create a custom answer file to be used in lieu of the one Setup auto-creates from the options chose within the Setup GUI. To do so, see the steps in this answer
  
  

From the Windows Setup GUI:

1. Open a terminal: Shift+F10
2. Wipe partition table and convert drive to GPT:

   DiskPart
   
   ::# List drives:
       Lis Dis
   
   ::# Select OS drive Windows is being installed to:
       Sel Dis <#>
   
   ::# Verify it's the correct drive:
       Det Dis
       Lis Par
   
   ::# Wipe partition table and convert (assumes no data on drive is being preserved)
       Clean
       Convert Gpt
   

   
   
3. Create boot partition:

   ::# For free space to be 200MB, 200*1.024 = RAW size of 205
       Cre Par EFI Offset=1024 Size=205
       Format Quick Fs=FAT32 Label="EFI"
       Cre Par Msr Size=16
   

   
   
4. Create OS partition:

   • Rest of the drive as the OS partition:

     Cre Par Pri Id=ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
     Format Quick Fs=NTFS Label="System"
     

   • Additional partitions after the [200GB] OS partition:

     ::# If storing User Data directories on a partition other than `C:` (recommended), 
     ::# max size required is ~300GB. Multiply size wanted by 1024: 200*1024=204800
         Cre Par Pri Size=204800 Id=ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
         Format Quick Fs=NTFS Label="System"
     

     
     
5. Create WinRE partition:

   ::# Should have minimum 320MB free for future WIM size increases
       Shrink Desired=1024 Minimum=1024
       Cre Par Pri Id=de94bba4-06d1-4d40-a16a-bfd50179d6ac
       Format Quick Fs=NTFS Label="WinRE"
       Gpt Attributes=0x8000000000000001
   

   
   
6. Close terminal and proceed through Setup GUI as normal

Answer 2

This is quite an old question, but I thought this knowledge would be useful to share since I spent a few hours digging for the answer.

It turns out you can manually create partitions during fresh install instead of relying on the automatic partition creation.

You can press Shift+F10 to start a terminal in the installation environment, then use diskpart to form the disk to your will. It has a built-in help system, and should be fairly simple to use.

I should include a disclaimer that this is potentially dangerous and can cause data loss, so make sure precious data is backed up before fiddling with partitions.

Information gleaned from: https://docs.microsoft.com/en-us/windows-hardware/manufacture/desktop/windows-setup-installing-using-the-mbr-or-gpt-partition-style

NOTE 1: (Gleaned from the built-in help) It should be noted that windows 10 requires a certain structure on a GPT disk to boot. On the disk from which you wish to boot, the EFI boot partition must be first, followed by the MSR partition, followed by data partitions. I was generous and gave MSR 20MB.

NOTE 2: diskpart spoon-feeds partition types to you: when creating a partition, you are given the option to create an EFI, MSR, or "ordinary" partition. The list can be displayed by running

help create partition

in the diskpart interface.