"Warning: no write permission" even with root

English Hardware
#1

First off Hello everyone on the forums.
I just installed 12.2 version on my Dell 14R N4010 laptop. I found that my brightness keys were not working. So I searched forums and found acpi_backlight=vendor and acpi_osi=linux option would work but it didn’t. Then I tried setting brightness using xbacklight. Still it wasn’t changing. Then I found that there is /sys/class/backlight/intel_backlight where I can specify actual_brightness.
I logged in as root and even after being root I get “Warning: no write permission” error while saving the file… I tried [SOLVED] Warning: No write permission… Even with root :frowning: - Ubuntu Forums](http://ubuntuforums.org/showthread.php?t=1711415) but in opensuse shutdown command doesn’t seem to have -rF option. Further, I tried this, But this doesn’t work for me either… What should I do to have read write access to / partition?

#2

Of course you cannot write to it since the file rights are set to read
only for that file, if you are root or not.


ls -l /sys/class/backlight/intel_backlight/actual_brightness

gives you -r–r–r–

If you want to change that try a


chmod u+w /sys/class/backlight/intel_backlight/actual_brightness

as root to make it writable. Be warned that I have no clue if it is safe
to do that.

–
PC: oS 12.2 x86_64 | i7-2600@3.40GHz | 16GB | KDE 4.8.4 | GeForce GT 420
ThinkPad E320: oS 12.2 x86_64 | i3@2.30GHz | 8GB | KDE 4.8.4 | HD 3000
eCAFE 800: oS 12.1 i586 | AMD Geode LX 800@500MHz | 512MB | KDE 3.5.10

#3

On 09/06/2012 12:06 PM, batbhai wrote:

> (http://ubuntuforums.org/showthread.php?t=1711415)
> (http://ubuntuforums.org/showthread.php?t=1711420)

as a general rule of thumb: use Ubuntu forums solutions when using
Ubuntu and use openSUSE forum solutions when using openSUSE…

its, kinda like: when driving a diesel vehicle use diesel…

forcing your searches to stay inside the openSUSE forums is easy, just
use google and their site specifier…just use a search string like:


site:forums.opensuse.org no write permission even as root

see for yourself:

https://www.google.com/search?q=site%3Aforums.opensuse.org+no+write+permission+even+as+root

by the way, i hope your “I logged in as root” does NOT mean you logged
into KDE, GNOME, LXDE or any other non-Windows desktop environment as
root! never do that, ever. if you don’t know how to avoid logging into
the GUI as root, please just ask…or see here: http://tinyurl.com/593e4c

–
dd http://tinyurl.com/DD-Caveat

#4

@martin_helm:
Thanks for replying mate!
I tried what you suggested but I get this error:
Could not create a backup file while saving /sys/class/backlight/int…cklight/actual_brightness

#5

Do not use an editor for that file, the usual way to set something into
such files is to use the echo command like that


su -
echo 1234 > /sys/class/backlight/intel_backlight/actual_brightness

of course replace 1234 with the value you want.

–
PC: oS 12.2 x86_64 | i7-2600@3.40GHz | 16GB | KDE 4.8.4 | GeForce GT 420
ThinkPad E320: oS 12.2 x86_64 | i3@2.30GHz | 8GB | KDE 4.8.4 | HD 3000
eCAFE 800: oS 12.1 i586 | AMD Geode LX 800@500MHz | 512MB | KDE 3.5.10

#6

:smiley: I should have thought of googling like that…and nope I am not logging into GNOME as root. I had just su-ed to modify that file value…I chown-ed that directory recursively but still it gives me “Could not create a backup file while saving /sys/class/backlight/int…cklight/actual_brightness” … :frowning:
Btw, is there no other way to change backlight apart from what I mentioned?

acpi_osi=Linux acpi_backlight=vendor

generally worked for all the threads I read…What may have gone wrong with my laptop?
my bootloader line reads

resume=/dev/disk/by-id/ata-ST9320325AS_6VD9RZMM-part7 splash=silent quiet showopts acpi_osi=Linux acpi_backlight=vendor

Was I supposed to do something else?

#7

Thanks for replying but that still gives me:

echo: write error: Input/output error

:frowning:

#8

Am 06.09.2012 13:18, schrieb Martin Helm:
> Do not use an editor for that file, the usual way to set something into
> such files is to use the echo command like that
>


> su -
> echo 1234 > /sys/class/backlight/intel_backlight/actual_brightness
>

of course replace 1234 with the value you want.

Btw I am not sure if the actual_brightness is meant to be set at all,
how did you come to the conclusion to edit that file?
I think you should set the value in
/sys/class/backlight/intel_backlight/brightness
but before you tinker with all that files, what about telling us a bit
about your hardware? The following information would be a starting point


hwinfo --gfxcard
/sbin/lspci -nnk | grep VGA -A 2

and maybe you should even start a new thread which mentions your real
problem with the backlight instead of one which asks for a solution of a
side effect.

–
PC: oS 12.2 x86_64 | i7-2600@3.40GHz | 16GB | KDE 4.8.4 | GeForce GT 420
ThinkPad E320: oS 12.2 x86_64 | i3@2.30GHz | 8GB | KDE 4.8.4 | HD 3000
eCAFE 800: oS 12.1 i586 | AMD Geode LX 800@500MHz | 512MB | KDE 3.5.10

#9

O yes! I should’ve changed /sys/class/backlight/intel_backlight/brightness insted! That worked! I will start a new thread adding this to after.local doesn’t change the brightness at startup with my hwinfo.* Ich bin Ihnen sehr dankbar!* :slight_smile: