Ubuntu 无法调节亮度的问题

这个问题虽然不大，但是很致命。因为电脑一直保持着高亮，对眼睛的伤害非常大，所以必须解决。

我是在ubuntu下遇到的问题，但是不是每个版本都有，也不是每个笔记本型号都会遇到,,, 我的笔记本是惠普的，在 12.04 和 13.10 上都有这个问题。

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参考论坛的帖子，找不到原帖了。

Debian7 下，笔记本上按Fn+《--- 调节亮度时，可以看到出现的图标亮度减少，可是实际不变。同样，在设置中调亮度也是一样。解决办法：
这种方法的基本使用条件是：intel 显卡对背光亮度起作用，在“/sys/class/backlight”下面有两个目录“acpi_video0”和“intel_backlight”，按亮度调节键时只对“acpi_video0”下面的“brightness”起作用，但真正对背光亮度起作用却是“intel_backlight”下面的“brightness”值

wrote a rules of "/etc/udev/rules.d/99-writeintelbacklight.rules" as below:

ACTION=="change", SUBSYSTEM=="backlight", RUN+="/usr/sbin/writeintelbacklight.sh"

A shell: "/usr/sbin/writeintelbacklight.sh"

#!/bin/bash

intelmaxbrightness=`cat /sys/class/backlight/intel_backlight/max_brightness`
acpimaxbrightness=`cat /sys/class/backlight/acpi_video0/max_brightness`
scale=`expr $intelmaxbrightness / $acpimaxbrightness`
acpibrightness=`cat /sys/class/backlight/acpi_video0/brightness`
newintelbrightness=`expr $acpibrightness * $scale`
curintelbrightness=`cat /sys/class/backlight/intel_backlight/actual_brightness`
if [ "$newintelbrightness" -ne "$curintelbrightness" ]
then
echo $newintelbrightness > /sys/class/backlight/intel_backlight/brightness
fi
exit 0

Of course, you need do a "sudo chmod +x /usr/sbin/writeintelbacklight.sh"

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上面的方法解决了我在12.04中的问题，但是在13.04中还是失灵了。

其实改变笔记本亮度，决定作用的就是修改 /sys/class/backlight/intel_backlight/brightness， 至少在我的笔记本是这样的。于是，我干脆写了脚本，内如如下：

echo 1000 > /sys/class/backlight/intel_backlight/brightness

1000 是一个我常用的亮度值。觉得需要的时候，执行一下这个命令,,, 凑合吧先。

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1. trying to echo /sys/class/backlight/acpi_video0/brightness : Permission denied

   Hi Community, 
   
   i'm new to UBUNTU. I've recently installed ubuntu 12.10 and have several issues. One of them is that my brightness always sets itself to 100% at a new boot. I've a line in /etc/rc.local: 
   
   

   Code:

   echo 7 > /sys/class/backlight/acpi_video0/brightness

   but it won't execute. Every boot the screen gets set to max.
   If i run the command logged in as root

   Code:

   sudo su

   it works.
   but 
   

   Code:

   mo@x1-carbon:~$ sudo echo 6> /sys/class/backlight/acpi_video0/brightness
   bash: /sys/class/backlight/acpi_video0/brightness: Permission denied

   gives me no permission. 
   
   What am I missing?
   
   Thanks for your help,
   m

2.  

   Re: trying to echo /sys/class/backlight/acpi_video0/brightness : Permission denied

   Your command gives elevated permissions to the echo command (which doesn't need them), but not to the part that redirects the output stream to the root-owned file (which does)
   
   In a terminal, you can either do
   
   

   Code:

   echo 7 | sudo tee /sys/class/backlight/acpi_video0/brightness

   which gives the elevated permission to the bit that really needs it, or
   
   

   Code:

   sudo sh -c "echo 7 > /sys/class/backlight/acpi_video0/brightness"

   which runs the whole command in a sudo shell
   
   HOWEVER you shouldn't use sudo at all in /etc/rc.local since it should be executed as root - something else must be going wrong there