`fbcon/cursor_blink` permissions reset at reboot

Question

Context

I need to stop the cursor from blinking on an external screen of my raspberry-pi in order to display a home-made interface on /dev/fb0.

For this purpose I created a group cursor_blink in which I put my user and changed the permissions of the file /sys/class/graphics/fbcon/cursor_blink as follow:

chown root:cursor_blink /sys/class/graphics/fbcon/cursor_blink
chmod 664 /sys/class/graphics/fbcon/cursor_blink

So my user in the group cursor_blink can write 1 or 0 to display and hide the cursor from the screen.

Problem

I had this working, but reinstalling it on another system makes that this file is now reset to the default permissions every time I reboot, the mode becomes again 600 and the owner root:root after reboot instead of 660 and root:cursor_blink

It seems that the file is recreated (some digging in the last edit times with stat corroborate this element).

Question

Is there a way to keep the permissions as set, and prevent them of being reset ?

Answer 1

For the moment the solution I found is to add a crontab task to correct the permissions at boot:

crontab -e

# ...
# add this line at the end of the file :

@reboot chown root:cursor_blink /sys/class/graphics/fbcon/cursor_blink && \
        chmod 664 /sys/class/graphics/fbcon/cursor_blink

Prerequisite: The group cursor_blink should be created and the user should be added to it before: usermod -a -G user cursor_blink.

If you have a better solution, feel free to add.