转载：http://forum.ubuntu.org.cn/viewtopic.php?f=42&t=239517

我使用苹果的无线键盘，一开始也碰到了相同的问题，后来在论坛上找到了答案，照着做了就ok了。
Change Function Key behavior
This section of the document describe how to change the behavior of ‘fn‘ key to better match what user expect. (See #201711, #162083)

Here a description of each behavior :

0 = disabled : Disable the ‘fn‘ key. Pressing ‘fn‘+‘F8‘ will behave like you only press ‘F8‘
1 = fkeyslast : Function keys are used as last key. Pressing ‘F8‘ key will act as a special key. Pressing ‘fn‘+‘F8‘ will behave like a F8.
2 = fkeysfirst : Function keys are used as first key. Pressing ‘F8‘ key will behave like a F8. Pressing ‘fn‘+‘F8‘ will act as special key (play/pause).
Ubuntu 9.04 and Newer
Temporarily
This section describe how to change the behavior of ‘fn‘ with immediate effect (Restarting will reset the configuration). Execute the following commands to change the fnmode parameters. See section above for a description of available value.

$ sudo bash
# echo 2 > /sys/module/hid_apple/parameters/fnmode
# exit