How do I set default brightness after boot?

Question

Linux Mint 12 (64bit), on an Acer Aspire 7730g. Upon every boot, the screen brightness is set very very low. Easily fixed via the function keys, but still a very annoying thing to do after every boot. Is there a way to set the brightness permanently?

NB: Interestingly, I had the same problem when Ubuntu was installed on the same laptop, so I'm a bit perplexed about how did this setting survive a complete OS reinstall?

dmesg output available here.

Another update: I don't know if this is related, but every time I reboot, my wireless is off, bluetooth is on, and Num Lock is off; all three the exact opposite of what I want them to be. If this is not related, it may become another question.

Does this help? http://blog.ishans.info/2011/09/25/set-brightness-automatically-at-the-startup-in-linux/ — , Feb 05 '12 at 15:23
@Nunoxic: Wouldn't this require me to add it for every user? The "blackout" occurs on login screen, so I'm not sure if this would be as practical. (Unless I misunderstood and this works even before login?) Also, unlike that guy's problem, there is no change of brightness on login/logout, is that a significant difference? — dr Hannibal Lecter, Feb 05 '12 at 16:52
I'm not so sure. You could give it a try if you are not averse to the idea of experimenting a little. It could, of course, be risky. — , Feb 05 '12 at 17:39
Just googling for a few of the suspect lines in the dmesg... I found a comment about nvidia cards not handling the vt.handoff parameter. Could you try booting w/o it and see if that makes any difference? The other line of interest is the "acer_wmi: Brightness must be controlled by generic video driver" — bsd, Feb 05 '12 at 17:48
@bdowning: Thanks for the suggestion, if the solution below stops working, I'll have to try it (though I'll have to learn _how_ first:)) — dr Hannibal Lecter, Feb 05 '12 at 19:56
One of the problems with hard coding an assigned value is that you might not get the behavior you desire when on battery power. My laptop handles this without any intervention but I don't use Ubuntu. To test once or twice you can edit the line for testing by interrupting grub during boot and editing the line — bsd, Feb 05 '12 at 20:24

score 11 · Accepted Answer · answered Feb 05 '12 at 17:36

11

Your laptop should have /sys/class/backlight. For example, /sys/class/backlight/acpi_video0/brightness. You can write (echo) values to this file to adjust brightness.

cat /sys/class/backlight/acpi_video0/max_brightness > /sys/class/backlight/acpi_video0/brightness

This will set the brightness to max. Just put it in an init script on boot.

answered Feb 05 '12 at 17:36

phemmer

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Many distros use the `/etc/rc.local` init script for running programs after boot. – Feb 05 '12 at 18:02
Success! I added that to `/etc/rc.local` as @hesse said and it works, half a second after the login screen shows up it toggles the brigthness. Thanks! – dr Hannibal Lecter Feb 05 '12 at 19:54

d3v1us · Answer 2 · 2013-01-22T09:05:12.353

my x120e's brightness constantly changing bothers me as well. surprisingly (but not), when i ran

gksudo dmesg > boot.messages

and opened boot.messages in a text editor, i noticed this message:

[Firmware Bug]: ACPI: No _BQC method, cannot determine initial brightness

multiple times, as well as some interesting others. paste that into Google and you'll find Cannibal's Candy [wordpress] - who provides an in-depth look at ACPI and a method for universally setting the screen brightness (+ so much more):

DSDT editing: Put an end to your ACPI woes

yep, prepare your mind to be blown. i'm working through CC's post right now, but thought i would share. best of luck!

running Linux Mint Debian (amd64) on a Thinkpad x120e

My goodness. This is hardcore. The link talks about learning a whole new language. I think I'll stick to changing the brightness manually for now! — LondonRob, Jul 26 '14 at 23:05

How do I set default brightness after boot?

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