After a Tweet from Edward Snowden giving Qubes OS a shout out, I’ve been fascinated with how it works. A desktop environment that makes it easy to run as many or as few applications as you want in different sandboxes virtual machines? That’s cool. Real cool. This is some security at a fundamental level that makes so much sense to my low grade tinfoil hat.

However, the machine I tried to run it on was a iMac with a Fusion drive that was already dual booting Windows. For some reason, I had forgot the very basic rule of Fusion drives.

You get one extra partition. No more.

It’s outlined in support documents and everything. So when I went to re partition for it, that broke Windows. I decided to cut my losses and erase the would-have-been Qubes partition and the Windows partition and then have the Boot Camp Assistant reclaim that space, remake the Boot Camp partition, and I’d go back to the way things were.

However, the Boot Camp Assistant in El Capitan gets incredibly confused if you don’t have one of two states:

  1. One single JHFS+ partition
  2. One JHFS+ and a Windows partition

At this point in time, I had neither of those states, so the BCA just complained. The Fusion logical partition didn’t show the free space in Disk Utility, so now I had a lot of wasted free space. Next step? Dog around in the diskutilmanual pages and figure out how to reclaim it. It wasn’t obvious to me. Having current backups, I just decided to erase everything clean and start fresh.

Here’s where things went from bad to worse. The Disk Utility in both the Recovery Partition and Internet Recovery would allow me to erase my existing Fusion partition, but not resize it.

Tapping the knowledge of former Apple co-worker, I discovered that the best way of solving this would be to break apart the Fusion scheme, and allow Disk Utility in Internet Recovery to see the “problem” and rebuild it. The tricky bit is that this is done by using diskutil to damage the file systems on both of the drives that make up the Fusion partition. It felt like a needless hack to do something that I’m sure has come up with users before.

So that’s what I did. Reinstalled the OS X from recovery and then updated it to El Capitan.

Time to Reinstall Windows 10

The BCA resized my partition, I booted into the Windows 10 installer that I already had ready before the original format of the first partition. And I got:

Setup was unable to create a new system partition or locate an existing system partition.

Apple Support has an article specifically for this error message. The summary of it is that Windows installer is confused by the storage space that it sees available. My first rodeo with Boot Camp a couple years ago, I ran afoul of this because I had some external hard drives plugged in. In this case, I had nothing plugged in.

After spending some time having DuckDuckGo find people with similar issues and some suggested solutions, I go with deleting the BOOTCAMP partition and having the Windows installer use the free space to do with what it will.

For a brief moment of hope bringing joy, the Windows installer goes on to try to start copying its installation files. Then:

Windows could not prepare the computer to boot into the next phase of installation.

I try to have the BCA undo my changes so I could have another go at it, but this took me all the way back to the top of this story.

Over the next day, I’d destroy the Fusion partition, reinstall OS X through Internet Recovery (why I didn’t make a USB installation drive, I couldn’t tell you), upgrade again to El Capitan, then make another crack at the previous story with some variation. Trying to download a new or different ISO from Microsoft, trying an older USB drive, burning the ISO to a DVD-R instead …

None of it worked.

The thing that stuck in my mind every single time was that the Windows installer would show all of the partitions on both drives that made up the Fusion drive, which I couldn’t clearly remember it doing on this machine my first go around. Also I never saw this in the screenshots that other people put forward on forum posts. I figured this was just because Fusion drive iMacs are probably less common than single drive setups.

Then came one of those moments in computer troubleshooting that makes a person absolutely feel like kicking themselves. I reset the PRAM and everything worked.

This should have been one of my first steps, as it is really one of the first steps that should be done for most kinds of troubleshooting of Apple hardware. Even some stuff that seems to be operating system or user space specific gets sorted by a PRAM reset.

tl;dr: Fusion setup issues? PRAM reset