How to activate FileVault when you don't have enough free space

[tongodeon]

Let's say you want to activate FileVault encryption on your Macintosh, but unfortunately you're using more than 50% of your hard drive's free space, and OSX doesn't have enough room to perform the copy.

You are not screwed. Here's what you do. For the purposes of this exercise let's assume that your username is "elvis".

1. Rsync your home directory onto an external firewire drive. You should be doing this anyway.
   
2. Create a new user account named "priscilla".
   Apple menu -> System Preferences -> System -> Accounts -> "Click the lock to make changes" -> "+" symbol to add a user
   
3. Check Allow user to administer this computer to give "priscilla" administrator privileges.
   
4. Log out of the "elvis" account.
   
5. Log in as "priscilla".
   
6. Check that all your user data really is actually on your external firewire drive. Check the size of the remote directory to make sure it's got as much stuff as you think it should have.
   
7. If you are very, very sure that you have backed your account up delete the "elvis" account.
   Apple menu -> System Preferences -> System -> Accounts
   "Click the lock to make changes"
   Select the "elvis" account
   "-" symbol to delete the user
   Delete all files immediately
   
8. Once "elvis" is deleted, make a new "elvis" account with the same password as the old "elvis" account. Check "allow user to administer this computer" if you want.
   
9. Log out as "priscilla", log in as "elvis".
   
10. Activate FileVault on the new "elvis" account.
    
11. Log out as "elvis", log in as "priscilla".
    
12. Mount the encrypted volume containing "elvis's" home directory. From the Terminal, run:
    sudo hdiutil attach ~elvis/elvis.sparseimage
    
13. Copy everything from the external firewire backup back into the "elvis" home directory. From the Terminal, run:
    sudo rsync -avE --delete /Volumes/backup/elvis /Volumes
    
14. Go watch a movie or something. Encrypting ~60GB of data might take a while.
    
15. Log out as "priscilla", log in as "elvis". Everything should be back to normal, except that your home directory now looks like a FileVault icon. If things do not look good, it's because you did not run rsync with the correct arguments.
    
16. Delete the "priscilla" account.
    
17. Using Disk Utility erase the free space that contains your unencrypted, deleted files. Stuart Romm forgot to do this part!
    Disk Utility -> Select your hard drive -> Erase -> Erase Free Space

Congradulations, your laptop is now protected against nosy customs agents.