⑴在Ubuntu系统中，有时会因为屏幕太亮或太暗需要调节屏幕亮度， 却发现屏幕亮度无法调整，或调整后无法保存，遇到这种问题该如何解决呢？
⑵Acer Aspire G
⑶NVIDIA GeForce GTM
⑷Ubuntu . x_
⑸其他情况解决方法类似。
⑹Fn不能调节屏幕的亮度。因为fn调节的是/sys/class/backlight/acpi_video/brightness文件，而I卡的文件是/sys/class/backlight/intel_backlight/brightness。
⑺启动系统，出现grub菜单时，按“e”编辑，在有linux内核路径那一行，添加“acpi_backlight=vendor”，如：
⑻linux /boot/vmlinuz-..--generic root=UUID=cbe-e-a-b-fadff ro acpi_backlight=vendor quiet splash
⑼如果能正常启动，且用fn能调节屏幕亮度，说明成功，接着下一步。
⑽二、修改grub
⑾sudo vi /etc/default/grub
⑿GRUB_CMDLINE_LINUX=“”
⒀GRUB_CMDLINE_LINUX=“acpi_backlight=vendor“
⒁我的grub文件如下：
⒂# If you change this file， run ‘update-grub’ afterwards to update
⒃# /boot/grub/grub.cfg.
⒄# For full documentation of the options in this file， see：
⒅# info -f grub -n ‘Simple configuration’
⒆GRUB_DEFAULT=
⒇#GRUB_HIDDEN_TIMEOUT=
⒈GRUB_HIDDEN_TIMEOUT_QUIET=true
⒉GRUB_TIMEOUT=
⒊GRUB_DISTRIBUTOR=`lsb_release -i -s 》 /dev/null || echo Debian`
⒋GRUB_CMDLINE_LINUX_DEFAULT=”quiet splash“
⒌GRUB_CMDLINE_LINUX=”acpi_backlight=vendor“
⒍# Unment to enable BadRAM filtering， modify to suit your needs
⒎# This works with Linux （no patch required and with any kernel that obtains
⒏# the memory map information from GRUB （GNU Mach， kernel of FreeBSD 。。。
⒐#GRUB_BADRAM=”x，xfefefefe，xabcdef，xefefefef“
⒑# Unment to disable graphical terminal （grub-pc only
⒒#GRUB_TERMINAL=console
⒓# The resolution used on graphical terminal
⒔# note that you can use only modes which your graphic card supports via VBE
⒕# you can see them in real GRUB with the mand `vbeinfo‘
⒖#GRUB_GFXMODE=x
⒗# Unment if you don’t want GRUB to pass ”root=UUID=xxx“ parameter to Linux
⒘#GRUB_DISABLE_LINUX_UUID=true
⒙# Unment to disable generation of recovery mode menu entries
⒚#GRUB_DISABLE_RECOVERY=”true“
⒛# Unment to get a beep at grub start
①#GRUB_INIT_TUNE=” “
②更新grub.cfg
③? ~ sudo update-grub
④查看grub.cfg 发现其中每个启动项都加入了“acpi_backlight=vendor”
⑤? ~ vi /boot/grub/grub.cfg
⑥设定屏幕初始亮度
⑦重启后发现，屏幕亮度又恢复为最大亮度。
⑧查看影响屏幕亮度的文件
⑨? ~ vi /sys/class/backlight/intel_backlight/brightness
⑩调节几次屏幕亮度发现其中数值会改变，我的笔记本数值范围为～。
Ⅰ手动修改该数值，会发现屏幕亮度随之改变（需要root用户执行：
ⅡPassword：
Ⅲroot ：/home/congbo# echo 》 /sys/class/backlight/intel_backlight/brightness
Ⅳ因此，将该语句添加到 /etc/rc.local 就能开机自动设定屏幕初始亮度了。
Ⅴ修改/etc/rc.local如下（需要root用户执行：
Ⅵ#！/bin/sh -e
Ⅶ# rc.local
Ⅷ# This script is executed at the end of each multiuser runlevel.
Ⅸ# Make sure that the script will “exit ″ on suess or any other
Ⅹ# value on error.
㈠# In order to enable or disable this script just change the execution
㈡# By default this script does nothing.
㈢echo 》 /sys/class/backlight/intel_backlight/brightness
㈣调节gamma值
㈤? ~ xgamma -gamma .
㈥-》 Red .， Green .， Blue .
㈦《- Red .， Green .， Blue .
㈧上面就是Ubuntu调节及保存屏幕亮度失败的解决方法了，出现这种问题的时候，先测试代码，再修改grub即可。