Improvements

tasks/main.yml

 ---
 # tasks file for sti_it.ldap_authentication
 - name: install required packages
-  apt:
-    pkg:
+  apt: 
+    name: "{{ item }}"
+    update_cache: yes
+    state: present
+  loop:
     - sssd
     - libpam-sss
     - libnss-sss
     - sssd-tools
     - autofs-ldap
     - ldap-utils
+  when: ansible_os_family == 'Debian'
 
 - name: make sure that the CA certs path exists
   file:

vars/main.yml

----
-# vars file for sti_it.ldap_authentication