Playing with Partitions in OS X


Here’s a little annoyance that I’ve come to find in Mac OS X’s disk utility application when playing around with disk partitions. Despite how powerful this app is, especially in comparison to its counterpart in Windows, it still presents the user with some limitations, however there sometimes is a workaround that may not be so straightforward to execute the required behavior. One such issue that I’ve faced is that of moving a partition’s location on the hard disk map; Apple make such a tedious task seem so trivial, however when you come to interact with it you realize that it’s not always as simple as drag-and-drop.

I picked this particular scenario where my OS X Lion partition was installed somewhere down the “hard disk map” (i.e. not at the beginning of the disk), because of a previous Linux install… well let’s just say that I was messing around with the OS. 😛 I eventually got rid of the partition that I had before it and decided I wanted to reclaim all the space that I had, but lo and behold, it wasn’t that straightforward.

The case where I wanted to fill up the space on the hard disk "above" Macintosh HD.

The main issue lies in the fact that when working with disk utility, you can’t change where a partition starts after you have created it, however you can change where it ends, by dragging the bottom right corner of the partition. There is a small trick however in Disk Utility that would help you to move partitions around, by a shuffling manner, granted there are some restrictions. The only catch (which should go without saying) is that you need to have enough (i.e. equal to or greater than) disk space to replicate the partition that you’re trying to move around.

This procedure is outlined below, however beware because it’s a very sensitive process, so it’s a good idea to make sure you have things backed up before going through this:

  1. Create a new volume in the blank space where you want to move the existing partition to.
  2. Give it a name that you can identify later so that you don’t want mix it up with your current partition.
  3. Boot into Recovery mode (available in OS X Lion) by holding down the “Option” key, and selecting “Recovery HD” from the boot menu that’s presented.
  4. Once booted, run Disk Utility.
  5. Select one of the volumes in the sidebar, then the Restore tab on the right.
  6. Drag the working Lion partition into the “Source” field and the new blank partition into the “Destination” field. Be sure not to set them backwards or you will lose ALL your data!
  7. Click “Restore”, and wait for it to clone the partition’s contents.
  8. Quit Disk Utility, and then choose Startup Disk from the Apple menu.
  9. Select the new partition that you just created.
  10. Reboot, and verify that everything is working right before proceeding.

If all went well and the system is up and running again, you can run Disk Utility, delete the original Lion partition that is located halfway down the disk map and then expand the new one into the space that you just freed up.

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