Mojave bootcamp assistant limits partition size

bootcampmojavepartition

MacBook Air 2015, Mojave installed, 125 GB flashdrive

We had a VM for windows, but with installing Mojave, deleted everything additional down to bare Mac OS and tried to install W10 with boot camp assistant (BCA). According disk utility, MacOS is taking 27 gb (including W10 iso file), free 93 gb. BCA partition keeps 47 gb for Mac, with remark 8 gb free. It will not go lower.

I used Disk Utility to make a disk partition of 30 gb for Mac, 90 gb for second partition. No problem. I deleted that partition, again disk space 120 gb, free 93. Tried again BCA, no dice, will not go below the 47 gb for Mac OS.

Any way to push this lower? I would like to go 85 gb for W10, 35 gb for Mac. That should be enough for both OS and some working space for extra programs, all larger data files go through external drives or cloud.

Update: Output from `diskutil list`

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     GUID_partition_scheme                         *121.3 GB   disk0
   1:                       EFI EFI                      209.7 MB   disk0s1
   2:                Apple_APFS Container disk2           30.0 GB   disk0s2
   3:                Apple_APFS Container disk1           75.0 GB   disk0s3
   4:      Microsoft Basic Data Data                      15.9 GB   disk0s4 

/dev/disk1 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +75.0 GB    disk1
                                 Physical Store disk0s3
   1:                APFS Volume W10                     745.5 KB   disk1s1

/dev/disk2 (synthesized):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      APFS Container Scheme -                      +30.0 GB    disk2
                                 Physical Store disk0s2
   1:                APFS Volume Macintosh HD            20.5 GB    disk2s1
   2:                APFS Volume Preboot                 44.4 MB    disk2s2
   3:                APFS Volume Recovery                522.7 MB   disk2s3
   4:                APFS Volume VM                      1.1 GB     disk2s4

Best Answer

If the BCA will not create the partitions in a way you want and you can, then consider installing W10 using a flash drive. While the use of a flash drive is not required, the procedure is simplified when one is employed. A Microsoft recommended install of W10 involves creating 3 new partitions which are listed below.

A Microsoft Reserved (MSR) partition of about 16 MB.
A Windows partition of at least 20 GB.
A recovery tools partition (WRE) of about 800 MB.

Even though Microsoft recommends a MSR, often the Boot Camp Assistant does not create this partition and Windows apparently works correctly when omitted. If the WRE partition is not created, then the software normally installed in this partition will be installed in the Windows partition. So technically, you only need the Windows partition. You can manually create the other partitions, but again this complicates the installation procedure. The exact Microsoft document explaining these requirements can be found at the Microsoft website UEFI/GPT-based hard drive partitions. Note: This document states the WRE should be 500 MB, but with the current W10 release, the size needs to be 800 MB. So, if you wish to create the three partitions, then the procedure would be as follows.

Boot from the flash drive.
When the first Windows 10 installation screen appears, enter a shift+F10 to open a Command Prompt window.
Run the diskpart command to create the partitions. In other words, create free space by deleting the single partition you created using macOS and create the three partitions in the free space.
Close the Command Prompt windows an proceed with the installation of Windows.

Instructions for creating a USB Windows 10 installer flash drive can be found as part of the accepted answer to Boot Camp Assistant fails to create the USB installer from the Windows 10 October 2018 Update.

Note: When installing using a flash drive, the Mac may reboot back to macOS before Windows finishes installing. If this happens, the select Windows from the "Startup Disk" pane of the "System Preferences" application, then click on the "Restart" button. The Windows installation process will pick up from where it left off.

Steps to Download the Windows Support Software

This example as done using a iMac (21.5-inch, Late 2013) running macOS Mojave Version 10.14.4.

Using the Finder application, open the Applications folder. Next, open the Utilities folder, which can be found in the Application folder.
Open the Boot Camp Assistant, which can be found in the Utilities folder.
From the menu bar, select Action, then Download Windows Support Software.
In the popup window, select where to store the download. In the image shown below, the Downloads folder was selected.
Below is an image of what to expect during the download.
Below is an image of what is shown when downloading completes. Some of the Windows Support Software files may be needed during the installation of Windows. Therefore, even though you are suppose to run the Windows Support Software application (Setup.exe) after installing Windows, you still need to copy this software to the same flash drive containing the Windows ISO files.

Installing Without the Windows Recovery Environment (WRE) Partition

Note: You probably can skip step 2.

Boot from the Windows 10 flash drive.
In this case, you will not need to use the diskpart command. However, you still could use the diskpart command to view the partitioning of the drives. When the image below appears, press the key combination shift+F10 to open a Command Prompt Window.

Enter the following commands.
```
diskpart
list disk
select disk 0
list partition
list volume
exit
```
Your results should be similar to what is shown in the image below.

Note: The output from list disk command must show a * in the Gpt column for Disk 0.

After entering the exit command to close the Command Prompt window, proceed with the installation.
If you encounter the image shown below, select Custom: Install Windows only (advanced).
When the image shown below appears, select Drive 0 Partition 3.
Confirm the selected partition is approximately 75 GB. Next, click on the Delete button, then click on the OK button in the popup window.
When the image shown below appears, select Drive 0 Unallocated Space.
Confirm the selected unallocated space is approximately 75 GB. Next, click on the New button, then click on the Apply button. Click on the OK button in the popup window.
The result should appear similar to what is shown below. Confirm the selected partition is approximately 75 GB. Click on the Next button to continue with the installation of Windows.

Note: If you do not what a Microsoft Reserved (MSR) partition, then you can delete the partition before proceeding. In this example, I did not delete this partition.

Related Solutions

MacOS – Can’t modify partitions

Thanks @Tetsujin. The listing looked a little screwy so I was a little hesitant to go mucking around with the command-line diskutil. But I ended up doing a

diskutil corestorage list

and then

diskutil corestorage delete [UUID of 50GB Logical Volume Group]

GUI Disk Utility correctly saw the 50 GB of empty space as part of the other Logical Volume Group and I was able to delete it and merge it back in fine.

Fusion Drive – Repairing Possible Mess-Up on 1TB iMac with BootCamp

Theoretically everything is fine with your Fusion Drive. Fusion Drives look like this. Disk0 is your SSD with 121 GB and disk1 is your HDD with ~1 TB (~1.121 TB summed up).

The larger parts of your SSD (disk0s2) and your HDD (disk1s2) are pooled to a CoreStorage LVG (Fusion Drive: disk3) with a size of 967.8 GB. The rest is reserved for EFIs, a Recovery HD (alltogether ~1.3 GB) and your old Windows partition - now probably free space (~152 GB).

The logical volume 'Macintosh HD' (967.8 GB) spans disk0s2 and disk1s2. This is the first 'Macintosh HD' in picture 1. The volume 'Macintosh HD' - it's the one visible on the desktop - should ideally also have about 967.8 GB. This is the second 'Macintosh HD' in picture 1.
In fact it has only 852.67 GB (see picture 3).

In the second picture the logical volume 'Macintosh HD' is the first listed in black, the volume 'Macintosh HD' is the second listed in black, the other two 'Macintosh HD's listed in grey are the parts of your SSD and HDD dedicated to the logical volume 'Macintosh HD'.

In my opinion something went wrong after deleting various partitions with the Bootcamp Assistant/Disk Utility or in Windows.

Preparation:

Detach any external drive (especially your external Time Machine backup drive)
Restart to Internet Recovery Mode by pressing alt cmd R at startup.
The prerequisites are the latest firmware update installed, either ethernet or WLAN (WPA/WPA2) and a router with DHCP activated.
On a 50 Mbps-line it takes about 4 min (presenting a small animated globe) to boot into a recovery netboot image which usually is loaded from an apple/akamai server.

I recommend ethernet because it's more reliable. If you are restricted to WIFI and the boot process fails, just restart your Mac until you succeed booting.

Alternatively you may start from a bootable installer thumb drive (preferably Mavericks or Yosemite) or a thumb drive containing a full system (preferably Mavericks or Yosemite).

Now you may either repair CoreStorage or rebuild your Fusion Drive:

'Repair CoreStorage' (not recommended):

First i would try to check the volume 'Macintosh HD' with Disk Utility. If the volume is corrupted consider a reinstall of Mac OS X.
If the volume is ok quit Disk Utility
Open Terminal and enter diskutil unmountDisk /dev/LVIdentifier and both diskutil unmountDisk /dev/DiskContainingApple_CoreStorageIdentifier
In your case: first diskutil unmountDisk /dev/disk3 then diskutil unmountDisk /dev/disk0 and diskutil unmountDisk /dev/disk1
remove the EFI NO NAME partition with gpt remove -i IndexNumberOfEFINoName DiskIdentifier:
gpt remove -i 4 disk1
Remount the CoreStorage disks and then the Logical Volume:
In your case: first diskutil mountDisk /dev/disk0 and diskutil mountDisk /dev/disk1 and then diskutil mount /dev/disk3.

enter gpt -r -vvv show /dev/diskIdentfierOfApple_CoreStorage to get infos of your HDD CoreStorage disk.
In your case: gpt -r -vvv show /dev/disk1
It should look like this:

-bash-3.2# gpt -r -vvv show /dev/disk1
gpt show: /dev/disk1: mediasize=1000204886016; sectorsize=512;         blocks=1953525168
gpt show: /dev/disk1: PMBR at sector 0
gpt show: /dev/disk1: Pri GPT at sector 1
gpt show: /dev/disk1: GPT partition: type=C12A7328-F81F-11D2-BA4B-00A0C93EC93B, start=40, size=409600
gpt show: /dev/disk1: GPT partition: type=53746F72-6167-11AA-AA11-00306543ECAC, start=409640, size=1671210848
gpt show: /dev/disk1: GPT partition: type=426F6F74-0000-11AA-AA11-00306543ECAC, start=1671620488, size=1269760
gpt show: /dev/disk1: Sec GPT at sector 1953525167                               
     start          size  index contents                                        
         0             1        PMBR                                            
         1             1        Pri GPT header                                  
         2            32        Pri GPT table                                   
        34             6
        40        409600      1 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
    409640    1671210848      2 GPT part - 53746F72-6167-11AA-AA11-00306543ECAC
1671620488       1269760      3 GPT part - 426F6F74-0000-11AA-AA11-00306543ECAC
1672890248     280634887
1953525135            32        Sec GPT table
1953525167             1        Sec GPT header

The free space on your HDD has 280634887 blocks. Please calculate the biggest block number dividable through 8. That's 280634880 blocks (á 512 bytes) which equals 143685058560 B or ~143.7 GB. Add the size of your HDD CoreStorage Physical Volume (852666400768 B) The result is 143685058560 B + 852666400768 B = 996351459328 B
Resize your HDD CoreStorage physical volume with diskutil cs resizeDisk HDDPVUUID newsize
In your case: diskutil cs resizeDisk 93892BE8-2B7F-4ABD-A4C3-984495DCD98D 996351459328b
Calculate the maximal size of your CoreStorage Logical Volume in diskutil cs list: (size disk0s2) + (size disk1s2) In your case that's 120988852224 B + 996351459328 B = 1117340311552 B. That should be the size of your refreshed Logical Volume Group.
Resize your Logical Volume with diskutil cs resizeVolume LVUUID LVGSize-128 MB In your case that's diskutil cs resizeVolume D237FFDC-7DA4-41D7-AC13-4CC7E5E8C0A0 1117212311552b. If you get an error (There is not enough free space...) choose a smaller size like 1117148311552b.
Quit Terminal and open Disk Utility.
Check your expanded CoreStorage Volume for errors.
Quit Disk Utility, choose your CS volume as startup disk and restart your Mac

'Rebuild Fusion Drive' (recommended if you have a Time Machine backup)

Booted to Internet Recovery Mode open Utilities → Terminal in the menubar and enter:
diskutil cs list to get the CoreStorage listing.
Copy the Logical Volume UUID, it's the fifth listed.
Now delete the Logical Volume with diskutil cs deleteVolume LVUUID.
In your case: diskutil cs deleteVolume D237FFDC-7DA4-41D7-AC13-4CC7E5E8C0A0.
Copy the Logical Volume Group UUID, it's the first listed in the listing of diskutil cs list.
Then delete the Logical Volume Group with diskutil cs delete LVGUUID.
In your case: diskutil cs delete 1EFE58BC-3613-44C4-86EE-D816F3B66E3E
Enter exit and quit 'Terminal'
Open 'Disk Utility'. Enter 'Ignore' if you are asked to fix the drives.
Choose your SSD and partition it: 1 Partition Mac OS X Extended (Journaled), hit the Options button and choose GUID Partiton table and hit OK and Apply.
Please check that the size is ~121 GB

Example:
Choose your HDD and partition it: 1 Partition Mac OS X Extended (Journaled), hit the Options button and choose GUID Partiton table and hit OK and Apply.
Please check that the size is ~1 TB

Example:
Quit Disk Utility and open Terminal
Enter diskutil list

Example (your disk identifiers and sizes are different of course: Your volume SSD probably has the Identifier disk0s2 and the size 121 GB and your volume HDD probably has the Identifier disk1s2 and the size 1.0 TB):
Enter diskutil cs create "Name" IdentifierSSD IdentifierHDD
In your case probably diskutil cs create "Macintosh HD" disk0s2 disk1s2.

Copy the resulting LVGUUID

Example:
Enter diskutil cs CreateVolume LVGUUID jhfs+ "Macintosh HD" 100%.

Example:
Enter diskutil cs list
Check the size of your Logical Volume. It should have the size ~1.121 TB

Example:
Quit Terminal
Open 'Disk Utility' and check your newly created volume for errors
Quit 'Disk Utility'
Attach your external Time Machine backup drive or check this answer if you use NAS or another network share.
Open 'Restore from Time Machine Backup'
Choose the appropriate Time Machine backup and restore your system
Reboot to your restored system.
Unmount and detach your Time Machine backup drive
Open 'Terminal' and enter 'diskutil list'
Check if your 'Recovery HD' is listed.
If your 'Recovery HD' is missing, usually reinstalling your current system with the latest available system installer (e.g. 'Install OS X Mavericks (10.9.5)' if Mavericks is currently installed) will recreate it without loosing any data. AFAIK Recovery Partition Creator 3.8 will NOT create a Recovery HD on CoreStorage volumes.
After reinstalling the system with the latest available system installer open App Store and install the latest security fixes.

Update: Output from diskutil list