English
When you boot the system you will see a menu which lists the various boot options. The top one will say Manjaro.
When you can see the word Manjaro and it is coloured green, press the letter “e” on your keyboard once.
This will take you to a menu where you can edit the options used by the computer when it boots.
Find the line which starts with the word “linux” and use the arrow keys on your keyboard to move the cursor to the end of that line.
Once you have reached the end of that line, press the spacebar once to add a space, then type the letters
acpi_backlight=video
one at a time. Make sure you double-check the letters to make sure they are correct. If they are not correct, press the backspace key to remove the letters and type them again.
Once you are certain the letters have been typed correctly, press the F10 key on your keyboard once.
The operating system will now begin to boot and you can check the journal entries for see if the error persists. Apparently you’re technical enough to know how to do that bit.
If the error persists, or you find you can no longer alter the backlight by pressing the backlight keys on your keyboard, then repeat the above steps but change the letters you add to line beginning “linux” to one of the other three options:
acpi_backlight=vendor
acpi_backlight=native
acpi_backlight=none
If one of these options works in the way you are hoping for, you can add this option permanently so you don’t have to type it every time you boot.
One way to do this is to open a terminal application (for example, click on the Applications menu and look for a program called “Terminal”).
Once you have opened a terminal application, type these letters:
sudo nano /etc/default/grub
Make sure the letters are correct. If they are not correct, use the backspace key to delete the letters and re-type them.
Now press the Enter key on your keyboard once. You will be asked to type your password to let you edit the file.
Type your password carefully. Make sure it is correct or you will get an “access denied” error and will have to try again.
Once you have typed your password, press the Enter key once.
The “nano” text editor will load and show you the content of the /etc/default/grub file.
Use the arrow keys on your keyboard to move the entry cursor down to the line which begins GRUB_CMDLINE_LINUX_DEFAULT.
Move the cursor to the end of that line and place it between the h and the “ characters so you can add letters after the word “splash”.
Press the spacebar key on your keyboard once to enter a space.
Then type the letters which match the working option you typed in when you booted the computer. As a reminder, that will be one of these options:
acpi_backlight=video
acpi_backlight=vendor
acpi_backlight=native
acpi_backlight=none
Make sure you check the letters you type to make sure they are correct. They must match the option exactly or they won’t work. Make sure the line ends with a quotation mark “.
If you make a mistake, use the Backspace key to delete the letters, then re-type them.
Once you are happy that you have typed the letters correctly press the key combination (that is, press and hold the first key, then press and release the second key, then release > the first key):
CTRL-O
CTRL-X
This will save the file (output to a file) and exit the nano editor.
You should now be back at the black terminal window.
Type the letters for this command:
sudo update-grub
and press the Enter key on your keyboard once.
You may have to enter your password again. If so, type your password, making sure you type it correctly. If you make a mistake you will get an “access denied” error and will have to try again. Press Enter to confirm the password.
If you have entered the command correctly GRUB will add the backlight option to its menu entry and it will be present for every boot in the future.
You can verify it works by rebooting your computer. Please use the “reboot” menu item rather than holding down the power button or using the reset button on the case (if there is > one).
This took me twenty minutes to write.
Moved from #technical-issues-and-assistance to #newbies as OP wanted steps rather than pointers
机器翻译
当你启动系统时，你会看到一个菜单，其中列出了各种启动选项。最上面的选项将显示Manjaro。
当你看到Manjaro这个词并且是绿色的时候，按一次键盘上的字母 “e”。
这将带你进入一个菜单，你可以编辑电脑启动时使用的选项。
找到以 “linux “开头的那一行，使用键盘上的方向键将光标移到该行的末尾。
一旦你到达该行的末尾，按一次空格键，增加一个空格，然后输入以下字母
1 | acpi_backlight=video |
一次一个。请确保你仔细检查这些字母，以确保它们是正确的。如果它们不正确，按退格键删除这些字母并重新输入。
一旦你确定字母已经输入正确，按一次键盘上的F10键。
现在操作系统将开始启动，你可以检查日志条目，看看错误是否持续存在。显然，你的技术水平足以知道如何做这一点。
如果错误仍然存在，或者你发现你不能再通过按键盘上的背光键来改变背光，那么重复上述步骤，但将你添加到 “linux “开头一行的字母改为其他三个选项之一。
1 | acpi_backlight=vendor |
如果这些选项中的一个以你希望的方式工作，你可以永久地添加这个选项，这样你就不必在每次开机时输入它。
一种方法是打开一个终端应用程序（例如，点击应用程序菜单，寻找一个名为 “终端 “的程序）。
一旦你打开了一个终端应用程序，输入这些字母。
1 | sudo nano /etc/default/grub |
确保这些字母是正确的。如果它们不正确，使用退格键删除这些字母，然后重新输入。
现在按一次键盘上的Enter键。你将被要求输入你的密码，让你编辑该文件。
仔细输入你的密码。确保它是正确的，否则你将得到一个 “拒绝访问 “的错误，并将不得不重新尝试。
一旦你输入了你的密码，按一次回车键。
nano “文本编辑器将加载并显示/etc/default/grub文件的内容。
使用键盘上的方向键，将输入光标向下移动到GRUB_CMDLINE_LINUX_DEFAULT开头的那一行。
将光标移到该行的末尾，并将其放在h和””字符之间，这样你就可以在 “splash “一词后面添加字母。
按一次键盘上的空格键，输入一个空格。
然后输入与你启动计算机时输入的工作选项相匹配的字母。作为提醒，这将是这些选项中的一个。
1 | acpi_backlight=video |
请确保你检查你输入的字母，以确保它们是正确的。它们必须与选项完全匹配，否则将无法工作。确保该行以引号”. “结束。
如果你犯了一个错误，使用退格键删除这些字母，然后重新输入。
一旦你确信你输入的字母是正确的，就按下组合键（即按住第一个键，然后按住第二个键，再松开第一个键）。
1 | CTRL-O |
这将保存文件（输出到一个文件）并退出nano编辑器。
现在你应该回到黑色的终端窗口。
输入这个命令的字母。
1 | sudo update-grub |
并按一次键盘上的回车键。
你可能需要再次输入你的密码。如果是这样，输入你的密码，确保你输入的密码正确。如果你犯了错误，你将得到一个 “拒绝访问 “的错误，并将不得不再次尝试。按回车键确认密码。
如果你输入的命令是正确的，GRUB将把背光选项添加到它的菜单项中，在以后的每次启动中都会出现。
你可以通过重启电脑来验证它的作用。请使用 “重启 “菜单项，而不是按住电源按钮或使用机箱上的复位按钮（如果有的话）。
这花了我二十分钟的时间来写。
从#技术问题和援助#移到#新手#，因为OP想要的是步骤而不是指点。