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I recently had to reinstall Lion. Now, when I boot the keyboard is not backlit when at the login screen. It used to be backlit when at the login screen.

I'm using a Macbook Air 11" July 2011 model. In System Preferences I have the checkbox: Automatically illuminate keyboard in low light checked. The setting for Turn off when computer is not used for: is set at Never.

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It appears that the problem is related to FileVault. When I turned FileVault off and rebooted in safe mode the problem went away. I could change the brightness of the screen and the keyboard at the login screen. Volume controls worked too. Now that I've turned FileVault back on the problem is back.

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I believe that's because, with FileVault 2 enabled, that initial "login" screen must be bypassed before OS X actually boots. Hence, no settings can be applied there - they're all still sitting encrypted on your disk. – Dan J Feb 21 '12 at 18:05
What you wrote makes sense. Thanks for the insight. – YequalsX Feb 21 '12 at 18:08

Have you tried turning up the keyboard backlight brightness at the login screen, logging in and restarting to see if it will keep your setting? Typically, the setting for the backlit keyboard is stored in the PRAM. Once setting the brightness to your desired level, it should retain the setting after a restart providing you don't reset the PRAM. Give it a shot.

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I am unable to change the brightness of the keyboard at the login screen. I can't change the brightness of the screen or the keyboard when I'm at the login screen. I have both at full brightness when I restart. Keyboard isn't backlit but screen is at full brightness. – YequalsX Feb 21 '12 at 13:00
So, what happens when you press the display brightness and keyboard backlight brightness keys on your keyboard at the login screen? Any prohibitory signs or sounds? Do the adjustment HUDs show themselves? – Matt Love Feb 21 '12 at 13:28
Nothing happens. No sounds, no change. Nothing. – YequalsX Feb 21 '12 at 15:41
Hmm, that's odd. Try resetting the PRAM. Restart and hold down the Command + Option + P + R keys until you hear the startup chime sound twice. – Matt Love Feb 21 '12 at 15:57
I tried this and it didn't work. I turned FileVault off and booted in safe mode. Then rebooted again in normal mode and the problem went away. I could change volume, screen brightness, and keyboard was backlit. Then I turned FileVault back on and rebooted and the problem was back. Thanks for your help. – YequalsX Feb 21 '12 at 17:33

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