Turning on the numeric keypad by default in Debian with Plasma

Every time we switch on a classroom computer running Debian with the Plasma desktop, the numeric keypad starts switched off. Students type their password using the numbers on the right, nothing appears, and they have to press Num Lock before trying again. It’s a small thing, but across twenty computers several times a day it gets annoying. Let’s see how to leave it on by default, both on the login screen and inside the desktop.

Why one setting isn’t enough

NumLock has to be turned on at two different moments:

• On the login screen (SDDM), which is where the password is typed.
• In the Plasma session, which may reset the keyboard state when it starts.

On top of that, Debian 13 starts Plasma on Wayland by default, and the classic numlockx tool doesn’t work there: it only works in X11 sessions. That’s why the script does four things, so it works in every case.

What the script does

1. Installs numlockx, the small utility that turns NumLock on under X11.
2. Configures SDDM by creating /etc/sddm.conf.d/numlock.conf with the option Numlock=on, so the keypad is already on at the login screen.
3. Creates a system-wide autostart entry in /etc/xdg/autostart/numlockx.desktop, which runs numlockx on whenever any user logs into an X11 session.
4. Sets Plasma’s default value in /etc/xdg/kcminputrc with NumLock=0 in the [Keyboard] section. Plasma reads 0 as “turn on at startup” (1 is off and 2 leaves it unchanged). This is the part that also works on Wayland.

Since everything is stored under /etc, the setting applies to every user on the computer, including users created later.

The script

Download it from the link at the top (activar-numlock.sh) or copy its contents into a file with the same name (the script’s messages are in Galician):

#!/bin/bash
# Activa o NumLock por defecto (pantalla de inicio SDDM + sesión KDE/X11)
# Equivalente local do playbook de Ansible da aula.
# Uso: sudo bash activar-numlock.sh

set -e

if [ "$(id -u)" -ne 0 ]; then
    echo "Este script debe executarse como root: sudo bash $0" >&2
    exit 1
fi

echo "[1/4] Instalando numlockx..."
apt-get update -qq
apt-get install -y numlockx

echo "[2/4] Configurando SDDM (pantalla de inicio)..."
install -d -m 0755 /etc/sddm.conf.d
cat > /etc/sddm.conf.d/numlock.conf <<'EOF'
[General]
Numlock=on
EOF
chmod 0644 /etc/sddm.conf.d/numlock.conf

echo "[3/4] Creando autostart global (numlockx on ao iniciar sesión)..."
cat > /etc/xdg/autostart/numlockx.desktop <<'EOF'
[Desktop Entry]
Type=Application
Name=Activar NumLock Aula
Exec=numlockx on
Icon=keyboard
NoDisplay=true
X-GNOME-Autostart-enabled=true
X-KDE-autostart-after=panel
EOF
chmod 0644 /etc/xdg/autostart/numlockx.desktop

echo "[4/4] Valor por defecto de KDE Plasma (tamén funciona en Wayland)..."
# NumLock=0 -> activado ao iniciar Plasma (1 = desactivado, 2 = sen cambios)
if [ -f /etc/xdg/kcminputrc ] && grep -q '^\[Keyboard\]' /etc/xdg/kcminputrc; then
    sed -i '/^\[Keyboard\]/,/^\[/{/^NumLock=/d}' /etc/xdg/kcminputrc
    sed -i '/^\[Keyboard\]/a NumLock=0' /etc/xdg/kcminputrc
else
    printf '\n[Keyboard]\nNumLock=0\n' >> /etc/xdg/kcminputrc
fi

# Activalo xa na sesión actual, se hai unha sesión X aberta
if [ -n "$SUDO_USER" ] && [ -n "$DISPLAY" ]; then
    sudo -u "$SUDO_USER" DISPLAY="$DISPLAY" numlockx on 2>/dev/null || true
fi

echo "Feito: NumLock configurado en $(hostname). Pecha sesión ou reinicia para comprobalo."

How to run it

Open a terminal (Konsole) and go to the folder where you saved the file. For example, if you left it in Downloads:

cd ~/Downloads

First give it execute permission, so the system treats it as a program rather than a plain text file:

chmod +x activar-numlock.sh

You can check it has the permission with ls -l activar-numlock.sh: there should be an x at the start of the line, for example -rwxr-xr-x.

Now run it as administrator with sudo, because it changes system files in /etc and installs a package:

sudo ./activar-numlock.sh

The leading ./ means the script is in the current folder. It will ask for your password and show steps 1 to 4 as it goes. If you run it without sudo, the script itself warns that it must run as root and does nothing.

When it finishes, log out or restart the computer. The keypad should already be on at the login screen, and it will stay on once you’re in the desktop.

If a user still has NumLock off

The /etc/xdg/kcminputrc file only sets the default value. If a user changed this option before, their personal settings (~/.config/kcminputrc) take priority. In that case, go to System Settings → Keyboard and set NumLock on Plasma Startup to Turn on. You can also delete the NumLock= line from that personal file so it picks up the system value again.

What if you have many computers? Use Ansible

If you manage the classroom with Ansible, there’s no need to go computer by computer: the playbook numlock-aula.yaml applies the setting to all of them at once from the teacher’s computer.

---
- name: Configurar e activar NumLock permanente na aula
  hosts: aula
  remote_user: root
  gather_facts: no  # Non necesitamos recoller facts, así vai máis rápido

  tasks:
    - name: Instalar numlockx para asegurar o control do teclado
      apt:
        name: numlockx
        state: present
        update_cache: yes

    - name: Asegurar que o directorio de configuración de SDDM existe
      file:
        path: /etc/sddm.conf.d
        state: directory
        mode: '0755'

    - name: Configurar SDDM para activar NumLock na pantalla de inicio
      copy:
        dest: /etc/sddm.conf.d/numlock.conf
        content: |
          [General]
          Numlock=on
        mode: '0644'

    - name: Crear activación forzada no Autostart global do sistema
      copy:
        dest: /etc/xdg/autostart/numlockx.desktop
        content: |
          [Desktop Entry]
          Type=Application
          Name=Activar NumLock Aula
          Exec=numlockx on
          Icon=keyboard
          NoDisplay=true
          X-GNOME-Autostart-enabled=true
          X-KDE-autostart-after=panel
        mode: '0644'

    - name: Valor por defecto de KDE Plasma (NumLock activado, tamén en Wayland)
      ini_file:
        path: /etc/xdg/kcminputrc
        section: Keyboard
        option: NumLock
        value: '0'  # 0 = activado, 1 = desactivado, 2 = sen cambios
        no_extra_spaces: yes
        mode: '0644'

    - name: Notificar fin do proceso
      debug:
        msg: "Configuración do NumLock aplicada e persistente en {{ inventory_hostname }}"

To use it you need an inventory with a group called aula and SSH access as root to the computers. For example, a file called inventario:

[aula]
pc01
pc02
pc03

Then run it like this (the .yaml file doesn’t need execute permission, because Ansible reads it):

ansible-playbook -i inventario numlock-aula.yaml

The playbook does the same four steps as the script, including the /etc/xdg/kcminputrc one, so it works the same in X11 and Wayland sessions. It uses the ini_file module, which comes with the usual Ansible install (Debian’s ansible package).