Erasing a duplicate Recovery Partition

When trying to get Bootcamp installed…

Yesterday I tried to get Windows 10 running on our Mac Mini that’s in use for testing Hedge. Took me ages to figure out why we couldn’t get the Bootcamp assistent to continue, after getting this alert:

Bootcamp Assistent

Googling around a bit didn’t give us much: apparently you can’t install Bootcamp on a disk with more than 1 partition. But according to Disk Utility we didn’t have any 🤔

Disk Utility

Terminals diskutil did give us a lead: we had a system with two Recovery HD partitions. We think something went wrong when we reinstalled El Capitan on a previously Yosemite running Mac, so we needed to get rid of one. But which one?

diskutil list output

Luckily, that turned out easy to find out: mount one of the Recovery HD partitions with diskutil mount disk0s3 and look for SystemVersion.plist

Recovery HD in Finder
SystemVersion.plist

Is this the current macOS version? Unmount it diskutil unmount disk0s3 and mount the next partition.

So, we identified the partition that needs to go. In our case it’sdisk0s04, but it will be different on your system. Make sure to check, don’t just copy these values.

“New and improved”

With the old Disk Utility app and a one-liner in Terminal it has always been possible to show system partitions.

defaults write com.apple.DiskUtility DUDebugMenuEnabled 1

used to give you…

Good Ol’ Disk Utility (screenshot by Macworld)

…everything. The new Disk Utility doesn’t have this feature, so we need a workaround.

Erase first, delete afterwards

Now that we know which partition we want to get rid of, we need to find a way to actually do so. First, we convert the it into something you can see in Disk Utility: a Journaled HFS+ partition.

diskutil eraseDisk JHFS+ UnusedPartition disk0s04

Now you can see the partition in Disk Utility, and it’s easy to delete it. Run Bootcamp Assistent afterwards, et voila…

Success 🎉
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