Dim screen when user is idle

Create the user profile which contains the following lines:

user-db:user
system-db:local

local is the name of a dconf database.

Create the directory /etc/dconf/db/local.d/ if it does not already exist.

Create the key file /etc/dconf/db/local.d/00-power to provide information for the local database.

# Specify the dconf path
[org/gnome/settings-daemon/plugins/power]

# Enable screen dimming
idle-dim=true

# Set brightness after dimming
idle-brightness=30

Create the key file /etc/dconf/db/local.d/00-session to provide information for the local database.

# Specify the dconf path
[org/gnome/desktop/session]

# The number of seconds of inactivity before the session is considered idle
idle-delay=uint32 300

You must include the uint32 along with the integer key values as shown.

To prevent the user from overriding these settings, create the file /etc/dconf/db/local.d/locks/power-saving with the following content:

# Lock screen dimming and idle timeout
/org/gnome/settings-daemon/plugins/power/idle-dim
/org/gnome/settings-daemon/plugins/power/idle-brightness
/org/gnome/desktop/session/idle-delay

If you want to let the user change these settings, skip this step.

Update the system databases:

# dconf update

Users must log out and back in again before the system-wide settings take effect.