* The problem
I've defined the following udev-rule in my configuration (full
configuration attached)
#+BEGIN_SRC scheme
(... some omitted lines ...)
(udev-service-type
config =>
(udev-configuration
(inherit config)
;; SEE:
https://unix.stackexchange.com/questions/459874/udev-doesnt-want-to-run-chgrp-and-chmod
(rules
`(,(udev-rule
"90-backlight.rules"
(string-append
"ACTION==\"add\","
"SUBSYSTEM==\"backlight\","
"RUN+=\"/run/current-system/profile/bin/chgrp video
/sys/class/backlight/intel_backlight/brightness\""
"\n"
))
,@(udev-configuration-rules config)
(... some omitted lines ...)
#+END_SRC
This made it possible to change the gorup for the file (see proof below)
#+BEGIN_SRC sh
ls -l /sys/class/backlight/intel_backlight/brightness
#+END_SRC
#+RESULTS:
#+BEGIN_EXAMPLE
-rw-r--r-- 1 root video 4096 Sep 17 20:48
/sys/class/backlight/intel_backlight/brightness
#+END_EXAMPLE
I'm user =rdrg= (see proof below)
#+BEGIN_SRC sh
whoami
#+END_SRC
#+RESULTS:
#+begin_example
rdrg
#+end_example
I belong to group =video= (see proof below)
#+BEGIN_SRC sh
cat /etc/group
#+END_SRC
#+RESULTS:
#+begin_example
root:x:0:
wheel:x:999:rdrg,rdrg-experiments
users:x:998:
nogroup:x:997:
tty:x:996:
dialout:x:995:
kmem:x:994:
input:x:993:
video:x:992:rdrg,rdrg-experiments,gdm
audio:x:991:rdrg,rdrg-experiments
netdev:x:990:rdrg,rdrg-experiments
lp:x:989:
disk:x:988:
floppy:x:987:
cdrom:x:986:
tape:x:985:
kvm:x:984:guixbuilder01,guixbuilder02,guixbuilder03,guixbuilder04,guixbuilder05,guixbuilder06,guixbuilder07,guixbuilder08,guixbuilder09,guixbuilder10
guixbuild:x:3:guixbuilder01,guixbuilder02,guixbuilder03,guixbuilder04,guixbuilder05,guixbuilder06,guixbuilder07,guixbuilder08,guixbuilder09,guixbuilder10
messagebus:x:983:
polkitd:x:982:
geoclue:x:981:
colord:x:980:
avahi:x:979:
scanner:x:978:
gdm:x:977:
sshd:x:976:
#+end_example
But I can't edit that file as a regular user (see proof below)
#+BEGIN_SRC sh
echo 0 > /sys/class/backlight/intel_backlight/brightness
echo Exit code: $?
#+END_SRC
#+RESULTS:
#+BEGIN_EXAMPLE
bash: /sys/class/backlight/intel_backlight/brightness: Permission denied
Exit code: 1
#+END_EXAMPLE
It is worth mentioning that I can edit that file as =sudo=
#+BEGIN_SRC sh
echo 0 | sudo tee /sys/class/backlight/intel_backlight/brightness
echo Exit code: $?
#+END_SRC
#+RESULTS:
#+BEGIN_EXAMPLE
0
Exit code: 0
#+END_EXAMPLE
* The questions
1. Why can't I edit =/sys/class/backlight/intel_backlight/brightness=
even though the file belongs to the =video= group?
2. What's the proper way to make it possible to edit
=/sys/class/backlight/intel_backlight/brightness=? I need to do this
because I want to define a keybinding in my windows manager that
changes the brightness.
(use-modules (gnu))
(use-service-modules
networking
ssh
avahi
;; sddm-service-type
sddm
;; gdm-service-type
xorg
;; %desktop-services
desktop)
(use-package-modules
ssh
certs)
(define %my-services
;; We need to modify the service. Otherwise, we get the following
;; error
;;
;; guix system: error: service 'guix-daemon' provided more than once
(modify-services
%desktop-services
(delete gdm-service-type)
(guix-service-type
config =>
(guix-configuration
(inherit config)
(discover? #t)
(authorized-keys
(append (list (local-file "./public-keys/delta.pub"))
%default-authorized-guix-keys
(udev-service-type
config =>
(udev-configuration
(inherit config)
;; SEE: https://unix.stackexchange.com/questions/459874/udev-doesnt-want-to-run-chgrp-and-chmod
(rules
`(,(udev-rule
"90-backlight.rules"
(string-append
"ACTION==\"add\","
"SUBSYSTEM==\"backlight\","
"RUN+=\"/run/current-system/profile/bin/chgrp video /sys/class/backlight/intel_backlight/brightness\""
"\n"))
,@(udev-configuration-rules config)))
(operating-system
(host-name "sony")
(locale "en_US.utf8")
(timezone "America/Lima")
(bootloader
(bootloader-configuration
(bootloader grub-efi-bootloader)
(targets '("/boot/efi"
(file-systems
(cons*
(file-system
(device (file-system-label "my-efi"))
(mount-point "/boot/efi")
(type "vfat"))
(file-system
(device (file-system-label "my-root"))
(mount-point "/")
(type "ext4"))
(file-system
(device (file-system-label "my-home"))
(mount-point "/home")
(type "ext4"))
%base-file-systems))
(users
(cons
(user-account
(name "rdrg")
(comment "This is a comment for user rdrg")
(group "users")
(supplementary-groups
'(;; Make the user a sudoer
"wheel"
;; Allow the user to play sound
"audio"
;; Allow the user to access the webcam
"video")))
%base-user-accounts))
;; Globally-installed packages
(packages
(cons*
;; This is mandatory. Otherw
