Dualboot on a Mac with FusionDrive

It was hard for me to find some info about this, since the CoreStorage commands are not documented in man diskutil, so I thought I’d share all this.

This is how I split my main volume in order to have a Windows Dual Boot.

First of all, list your CoreStorage logical volumes using

diskutil cs list

Then, find the Logical Volume you want to shrink, the line should be something like :


Get that identifier, and simply do

sudo diskutil cs resizeStack XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX 215g NTFS-3G WINDOWS 35g

Where :

You’re now good to go !


resizeStack hidden documentation :

Resize both a logical volume and its underlying physical volume in a single
operation. The setup must be simple: Exactly one logical volume and one
related physical volume can, and must, exist.
If this is a shrink operation, you can optionally request that new partitions
be created in the newly-formed free space gap.

This awesome blog post : “Undocumented corestorage commands”

This gist : “OS X Lion diskutil commands (documented and hidden).sh”

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