Enable display manager lightdm by default

tasks/xfce4_configuration.yml

@@ -9,3 +9,38 @@
   service: name="gdm" state="restarted"
   when: _shell_output.changed
 
+- name: Install lightdm
+  apt:
+    name: ["lightdm"]
+    state: present
+
+- name: Check current display manager
+  shell: "cat /etc/X11/default-display-manager"
+  register: _current_display_manager
+  changed_when: false
+
+- name: Switch to lightdm as default display manager
+  block:
+  - name: Set default display manager
+    copy:
+      dest: "/etc/X11/default-display-manager"
+      content: "/usr/sbin/lightdm"
+      owner: root
+      mode: 0644
+
+  - name: reconfigure display manager
+    shell: "DEBIAN_FRONTEND=noninteractive DEBCONF_NONINTERACTIVE_SEEN=true /usr/sbin/dpkg-reconfigure lightdm"
+
+  - name: Stop and disable gdm
+    service:
+      name: gdm
+      state: stopped
+      enabled: false
+
+  - name: Start and enable lightdm
+    service:
+      name: lightdm
+      state: started
+      enabled: true
+
+  when: _current_display_manager.stdout != "/usr/sbin/lightdm"