Can't erase Macintosh HD (FileVault active)

In my case helped starting "clean" restoration from my Time Machine backup copy of my device (Ctrl+Option+R during boot sequence start). During restoration process device prompted that my disk will b erased and I wil have to set up FileVault anew from settings after retoration.

In my case it was a Fusion Drive. NOT a separate SSD. Hope this helpes

Turn off FileVault, and then you can partition and format the drive. Without doing this you will have to use Terminal commands to essentially do the same thing.

If you want to use the Terminal, then reboot with the Command-R keys held to get to the OS X tools window. In here, choose "Terminal" from the Utilities menu, and then run the following command:

diskutil cs list

With this command entered, you should see a hierarchical tree of the encrypted volume, with the first entry being the core storage volume group. Get the UUID from this group, and use it int he following command:

diskutil cs delete UUID

See this screenshot for what this should look like (UUID is circled in RED, and typed commands are in BLUE):

Absolutely. While filevault's contents is only readable by someone with the password, erasing the system and turning off FileVault is something that a new owner will have to do anyway in order to use the system.

If your drive is encrypted then destroying the volume group as I described in the Terminal will render all data useless, as it will be garbled information to anyone who tries to retrieve it.

If you instead disable FileVault and allow the system to decrypt the drive before formatting, then using a multi-pass erase will be one way to secure the data, though for most intents and purposes (the vast majority) using a simple single pass write to zeros will be enough.

Do keep in mind that if your system has an SSD, then writing to zeros and using 7-pass erase features is not recommended. In some cases it can give problems, but otherwise it will simply wear out the drive faster.

A seven pass erase is extreme overkill. There's nothing out there for the general public that can retrieve anything that's been covered by even a single pass erase. Plus, you'd be waiting a VERY long time for a seven pass erase to complete. On top of that, after the single pass erase, you'll be writing over the drive again with a fresh install of the OS. No one you're selling the Mac to is going to able to recover any old data.

Just imagine doing a 35-pass erase...ugh! 😀

Additionally, you're showing that you are running Mountain Lion - if your machine was purchased in 2011, it most likely came with Lion?

If that is the case, you need to erase the hard drive completely and reinstall the original OS as any OS obtained at the app store is not transferable. The buyer would never be able to reinstall the OS, as it is tied to your Apple ID forever.

In order to do that, you need to use Internet Recovery - Command + Option + R - which should install the original OS (rather than the regular recovery which will reinstall the current OS). If the machine came with an install DVD, you would need to use that to reinstall.

Just imagine doing a 35-pass erase...ugh! 😀

Hmm, let's see. I'm 56 now. If I start a 35 pass erase on a 2 TB drive, it should be done when I retire. 😁

Good catch, babowa!

How can I possibly sell my MBA to somebody I don't know with my Apple credentials already into the system?

That's what babowa was explaining; you can't, and don't.

The legal way to sell the Mac is by installing the OS it came with. Assuming babowa is correct, and it came with Lion, you restart and hold down the Command+Option+R keys to do an Internet Recovery. The OS that matches what the Mac came with will be installed.

If the buyer wants Mountain Lion, they'll have to purchase it themselves under their own App Store account.

Assuming babowa is correct, and it came with Lion, you restart and hold down the Command+Option+R keys to do an Internet Recovery. The OS that matches what the Mac came with will be installed.

These are the results testing has produced (testing done by various people here including myself and Red Dwarf and elsewhere and some have been working on a detailed user tip because the whole thing is so convoluting):

Internet Recovery (displaying a spinning globe while accessing Apple's servers): erase drive > no Apple ID required > installs original OS (perfect for selling as the buyer is able to get to the app store and purchase things with his/her own Apple ID)

Recovery: Apple ID required > installs current OS

Disclaimer (haha): one person reported that during one test with internet recovery, the current OS was installed; however, most of the time, the original OS was installed as intended. So, results weren't 100%.