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I am trying to follow instructions from here to enable backlight for my keyboard on Dell Vostro 3350.

I want to change the contents of a /sys/class/leds/dell::kbd_backlight/brightness file, which containts 0, to 3.

After runnig echo 3 | sudo tee brightness, the file still contains 0.

If I try to open it and edit in nano (using sudo), then after I save the changes and exit, the file still conatains 0.

If I try to open it and edit in gedit (using sudo), it does not allow me to save the file, showing the following message: Could not create a backup file while saving “/sys/devices/platform/de…:kbd_backlight/brightness”. Pressing 'Save anyway' does not have any effect (the file still contains 0).

I am running Ubuntu 15.10.

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Nick To
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  • Have you tried the other solution suggested by Pilot6: sudo tee /sys/class/leds/asus::kbd_backlight/brightness <<< 3 – Rohn Adams Aug 30 '16 at 23:19
  • Have you made sure that the system doesn't immediately overwrite the file with a 0 again? – Aly Aug 30 '16 at 23:25
  • Your link is to an Asus Zenbook laptop. According to google your Dell backlit keyboard is controlled with Fn + F6 just like my Dell Inspiron 17R SE 7220. Coincidentally my Logictech Wireless Backlit Keyboard also uses same key combination to brighten keys. You should not use sudo gedit as things can get messed up. Use gksudo gedit instead. – WinEunuuchs2Unix Aug 30 '16 at 23:36
  • @WinEunuuchs2Unix thanks for pointing that out! I didn't notice the asus:: vs dell:: difference in that one particular command. I mistakenly assumed he had pulled the commands he tried from the thread I linked. – Rohn Adams Aug 30 '16 at 23:52

2 Answers2

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The /sys directory is a special directory that is maintained by the system to provide information that you can view to see the state of your system. The file you are examining and trying to edit is being maintained by the system and is showing you the system's state. If the state changes you'll see the difference.

There are various facilities to control the features of your Laptop. Try xset to set the state.

Try (a variation such as):

$ xset led 3

Look at (https://askubuntu.com/a/18628/29012):

#!/bin/bash
if [ -f /tmp/keyboard_light ]; then
xset -led 3 && rm /tmp/keyboard_light
else
xset led 3 && touch /tmp/keyboard_light
fi

If that works and controls your back-light, you'll then see a difference in the file you're trying to edit.

By the way you can type this command to see the xset features that are recognized and their settings:

$ xset q
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L. D. James
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The link your provided is to an Asus Zenbook laptop which has a different ACPI than your Dell Vostro 3350 laptop.

Your laptop keyboard is turned on with Fn+F6 key (according to Google). Simply use these keys together to turn on backlit and cycle through brightness (brighter and brighter until off then on again).

When I bought my used Dell Inspiron 17R SE 7220 the owner told me it didn't have a backlit keyboard which contradicted marketing materials. After purchase I did some research and learned the same Fn+F6 for your Dell works on my laptop too. It seems many users don't know this key combination in the Dell world based on google searches.

Even my Logitech Wireless Backlit Keyboard uses Fn+F6 to turn up key brightness so it seems a quasi-industry standard.

I didn't answer your question on how to change a file (doesn't exist on my system BTW) but solved your real problem of turning on your backlit keyboard and controlling key brightness. Hopefully saved you a whole bunch of time too.

WinEunuuchs2Unix
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