Resize TrueCrypt Volumes on Mac OS

Follow these instructions to resize TrueCrypt volumes on Mac OS without losing your data.

** Definitely backup your stuff (If your not already, omg.) before attempting this on a live system.

** Proceed at your own risk! This process works great for me, but you may have different results. I am not responsible for anything 🙂


  • Access to a win* box
  • TrueCrypt v6.2a installed on win* box
  • Download extcv binaries, available at
  • TrueCrypt volume must not have any ‘hidden’ volumes (they will be destroyed)
  • Filesystem on the TrueCrypt volume must use the GUID partition scheme and be formatted as HFS+ (aka Mac OS Extended Journaled)
  • Unmount the TrueCrypt image before starting.

Ok, now lets get down to business…

  1. Launch ‘extcv’ on the win* box.
  2. Select the file that contains your TrueCrypt volume.
  3. Enter the new size and go.

* I am assuming you have a solution to move or access your TrueCrypt file from the win and Mac boxes. I personally just used a WinXP vm in Parallels and used shared folders to access the TrueCrypt file on the Mac.

  1. Mount the TrueCrypt volume on your Mac.
  2. Launch ‘’.
  3. View your volumes and current sizes by executing ‘diskutil list’

In my scenario, ‘/dev/disk3’ is the TrueCrypt volume and you can see that the size is now 524MB. The partition I want to expand is ‘disk3s1’ which is currently 100MB.

  1. View the size limits by executing ‘diskutil resizeVolume disk3s1 limits’

Clearly you see that the max size our new partition could be is 389.8MB

  1. Now we are going to do the live resize. This is the scary part (double check your backups before completing this step)!

I want my partition to be approximately 250MB. Please read the docs ‘man diskutil’ to see if you want to use different syntax.

Execute ‘diskutil resizeVolume disk3s1 250M’

Confirm the data is still there:

Great, you made it to the end! Hope you enjoyed… Please post comments if you figure out better solutions.