Partitioning a Mac hard drive

[John Emmas]

I restored my hard drive to its original condition (i.e. with a single Mojave partition covering the whole 1TB drive). I also installed the windows.iso file in my Documents folder and ran the Boot Camp installer.

The first thing it does is to spend around 15mins downloading some extra components. At the end of this, it shows a password box saying that Boot Camp is trying to add a new helper tool (and asking for my password). After I give the password I press the button marked "Add Helper" - but I then immediately see an error message saying "An error occurred while copying the Windows installation files" (the process then terminates).

I've read some stuff on the internet about Mojave not supporting Boot Camp on certain Macs (mostly iMac) but the Mac Pro is compatible according to this list:-

https://support.apple.com/en-gb/HT201468

So I'm stumped. Should I start a new thread about this..?

[Edit...] Groan... apparently this happens because the Windows 10 ISO file is greater than 4GB:-

https://twocanoes.com/using-larger-windows-10-isos-with-boot-camp-assistant/

 

[honestone]

Which version of Mojave are you running? V10.14.3 was just recently released. You can obtain the OS 10.14.3 Combo Updater from here:

https://support.apple.com/kb/DL1992?locale=en_US

Not sure if that update (or the OS 10.14.2 update that was released in early December) resolves the "Windows 10 ISO file is greater than 4GB" you pointed out above, but it is always best to have the latest version of of whatever software you sue, and especially the Mac OS.

 

[John Emmas]

Thanks honestone - it's showing up as 10.14.2. I followed the link you supplied but it doesn't say anything about 10.14.3 fixing the Boot Camp issue so I'm assuming it probably doesn't (in fact, I'm wondering if Apple are even aware of it yet... )

 

[honestone]

You're welcome. Yeah, I saw nothing in the descriptions of either update (ie, 10.14.2 and 10.14.3) about anything to do with Boot Camp/Windows. Also, Apple might take the attitude that it is a Windows issue. Still, it is always best to keep up to date, and especially with some Security fixes included.

I also wonder if this is a similar issue with using either Parallels Desktop:

https://www.macupdate.com/app/mac/21252/parallels-desktop

or VMware Fusion:

https://www.macupdate.com/app/mac/23593/vmware-fusion

 

[Lufbrarunner]

I set up windows using bootcamp on an imac running Mojave, no problems. Not sure if I was using 10.14.1 or 10.14.2

 

[John Emmas]

Hi Lufbrarunner - do you still have your Win10 ISO file available? My guess is that you probably installed it some time ago (when the file was still below 4GB). The latest version is only just slightly higher than 4GB.

Is it possible for me to keep Mojave but somehow go back to an earlier version of Boot Camp Assistant (one that'll work with Win7 or Win8)? If that's not possible I think I'll probably need to ditch Mojave and go back to an earlier version of OS-X. Maybe that'd be easier anyway?

 

[Lufbrarunner]

Hi John, my Windows 10 iso weighs in at 4.38gb

 

[John Emmas]

Wow, that's a bit weird... The version I downloaded at the weekend is actually slightly smaller (4.05GB) but it's reacting exactly like the twocanoes article I posted earlier:-

https://twocanoes.com/using-larger-windows-10-isos-with-boot-camp-assistant/

Is yours a disk file or is it on DVD? Maybe I need to use Microsoft's official install disk?

 

[Lufbrarunner]

I downloaded the ISO from the microsoft website.

 

[John Emmas]

I read some articles which suggested that the last Win10 installer that'd work with Mojave's Boot Camp was installer version 1703 (in fact, one of the articles had a helpful download link for it). So I downloaded the 1703 installer but it gives me exactly the same problems.

I can't help wondering if something's timing out here. At the start of the Boot Camp process it goes through a lengthy procedure called "Downloading Windows support software" (although from what I've read, these are some kind of Boot Camp helpers - rather than being actual Windows software). That process typically takes 15-20 minutes for me. I don't know exactly what's being downloaded but is there any way to find out so I could "pre-download" it somehow?

BTW honestone anf lufbrarunner - have either of you done this on a Mac Pro? I've read other articles which suggest that Mojave's Boot Camp Assistant won't work on certain mac types - although the Mac Pro was (supposedly) one of the types which does work

 

[Lufbrarunner]

The support software should be available for download from the apple support site.

 

[honestone]

Sorry John, but I have never done this. One thing that sticks out from that article you have a link for is the FAT32 format. Why not format the partition as ExFAT? That will get over the size restriction of any file used on that partition. Is the FAT32 format a Boot Camp requirement?

 

[Lufbrarunner]

BTW honestone anf lufbrarunner - have either of you done this on a Mac Pro? I've read other articles which suggest that Mojave's Boot Camp Assistant won't work on certain mac types - although the Mac Pro was (supposedly) one of the types which does work

I have only done this on an iMac, the only problem I encountered was my apple bleuetooth keyboard would not work on the Windows side so I used a spare wired keyboard.

 

[John Emmas]

Why not format the partition as ExFAT? That will get over the size restriction of any file used on that partition. Is the FAT32 format a Boot Camp requirement?

AFAIK it is (I don't think Boot Camp gives me any option for formatting). However - we might have discovered something here...

My disk size is 1TB. When Boot Camp tries to partition it, the smallest Windows partition it'll create is 96GB. The error then occurs while trying to format the 96GB partition. I don't know if Boot Camp formats the partition itself or if it passes control to Windows - BUT - if it passes control to Windows, Windows apparently cannot format a FAT32 partition greater than 32GB. It can work with larger partitions - but cannot format them. I've a gut feeling that this is very likely where the problem lies...

 

[Lufbrarunner]

From what I remember Boot camp will create the partition but it will need to be formatted, by windows, near the start of the windows install process

 

[John Emmas]

Does anyone here have a contact at Apple? Or a way for me to flag this up to them? I'm pretty sure now that the 96GB partition size is the problem here.

 

[honestone]

AFAIK it is (I don't think Boot Camp gives me any option for formatting). However - we might have discovered something here...

My disk size is 1TB. When Boot Camp tries to partition it, the smallest Windows partition it'll create is 96GB. The error then occurs while trying to format the 96GB partition. I don't know if Boot Camp formats the partition itself or if it passes control to Windows - BUT - if it passes control to Windows, Windows apparently cannot format a FAT32 partition greater than 32GB. It can work with larger partitions - but cannot format them. I've a gut feeling that this is very likely where the problem lies...

Based on this:

https://support.apple.com/en-us/HT201468

it seems that via Step 4, the formatting of the Windows partition occurs. But that step states that the Windows Installer does the formatting on the BOOTCAMP partition (created in step 3 above of those instructions).

Hence, it seems that the possible choice of formatting that partition as either FAT32 or ExFAT is at that step. Is there a choice at that step? What happens if after step 3, one uses Disk Utility to format that BOOTCAMP partition as ExFAT? Wonder what the Windows Installer does with that partition already formatted?

 

[John Emmas]

Thanks honestone but how would I even run the Windows installer (after formatting that partition)? Can I simply double-click on an ISO file?? I'd assumed Boot Camp takes care of all that somehow...

Interestingly, that Apple article suggested that Boot Camp should re-start the machine in between Step 3 and Step 4 but that's not what I'm seeing here. The partition does get created at Step 3 but then something (presumably Windows) immediately tries to format it (without any intervening re-start).

 

[honestone]

Actually, Step 3 involves running Boot Camp Assistant for 1) repartitioning the startup disk and 2) downloading related software drivers for Windows. Then the Mac restarts to the Windows installer (in Step 4). From there, one selects that BOOTCAMP partition created in Step 3, and then click on Format.

Given that happens automatically, after Step 4 starts (but no Formatting), quit that process, launch Disk Utility, and format that BOOTCAMP partition as ExFAT.

Maybe someone else can "chime in" regarding all this. It is perplexing, though, that Lufbrarunner was able to do this process without a "hitch".

 

[John Emmas]

after Step 4 starts (but no Formatting), quit that process, launch Disk Utility, and format that BOOTCAMP partition as ExFAT.

Maybe someone else can "chime in" regarding all this. It is perplexing, though, that Lufbrarunner was able to do this process without a "hitch".

Okay, I've only just woken up this morning but I'll try your ExFAT suggestion after I've had some breakfast.!

Lufbrarunner - what size was the Windows partition you created (and what was your overall disk size?) In my case the overall disk is 1TB and Boot Camp won't let me create a Windows volume any less than 96GB.