Bypass FileVault Password on Startup by Rebooting From Terminal
OS X: FileVault protects your Mac perfectly. Every time you boot, it asks for your password. However, if you are troubleshooting or providing remote support, it will be difficult to enter it every time. Fortunately, you can bypass the password requirement once with this terminal command.
Instead of rebooting from the Apple menu, enter the following command in Terminal:
sudo fdesetup authrestart
This will immediately restart your Mac without warning, so save your work. The next time you restart, FileVault will run normally unless you type this command again in a terminal.
Apple explains that this does not work on all Macs. To see if it works on yours, enter this command:
fdesetup supports autrestart
If the answer is TRUE , then you are golden.
OS X: Macs Supporting FileVault Authenticated Restart | Problems with Apple via Mac