Just wanted to share my experience attempting to partition/erase my MBA's SSD via the recovery system (command-R at the boot up chime). What I basically wanted to do was erase the partitions (2) that I had on the SSD, and replace them with one new, empty partition. Logically, I went over to the SSD in the sidebar from the recovery's Disk Utility, then "Partition", and from the drop down menu, "1 partition". So, what followed next was basically the recovery being unable to unmount the 2 partitions. I tried *everything* to unmount/get them to unmount, starting with erasing their contents, and attempting to restore the image of my external clone onto the SSD via the "Restore" tab. I tried to repair the disk(s), different filesystems, alll for nothing. I couldn't repartition the drive, period. What ended up happening was that I booted into my cloned external drive, launched up Disk Utility from there, and went about erasing and repartitioning the SSD as one, new partition. It worked, flawlessly (and thankfully, I was out of ideas of how to proceed next, really was getting worried there was a hardware issue with the drive). All that just to say that if you're unable to partition your internal hard drive via the recovery partition (which, goes without saying, resides on the same partition as your startup system), then try giving Carbon Copy Cloner or SuperDuper! a spin, booting from the cloned drive, and running Disk Utility from there. Naturally, the next step was to reinstall OS X onto the empty partition. I had to manually copy over the DMG from my other Mac (seeing as the recovery partition was gone at that point), and load it up from the external. From there, the installation took over and continued as it should after a restart. Solved my issue. Hope you don't run into it, but if you do, that's my two cents. EDIT: Seems like single-user mode could've helped me out in this situation.