ansible-roles/deb-set-hostname/tasks/main.yml

---
- name: Set the hostname
  hostname: name={{ hostname }}
  when: hostname is defined
  tags: bootstrap

- name: Add the hostname to /etc/hosts
  shell: grep -v {{ ansible_default_ipv4.address }} /etc/hosts > /etc/hosts.tmp ; echo "{{ ansible_default_ipv4.address }} {{ hostname }} {{ ansible_hostname }}" >> /etc/hosts.tmp ; /bin/mv /etc/hosts.tmp /etc/hosts
  when: hostname is defined
  tags: bootstrap