feat(hostname): manage hostnames and hosts

roles/hostname/README.md

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+# Hostname management role
+
+This role manages all hostnames of the target server,
+both `/etc/hostname` and additional hostnames in
+`/etc/hosts`.
+
+## Usage
+
+At the bare minimum, you need to specify `hostname_fqdn`,
+this is the primary hostname of the target, which ends up
+in `/etc/hostname`.
+
+You can specify additional hostnames for `/etc/hosts` in
+`hostname_extra_hosts` in the form of `{ip, fqdn, alias[] }`,
+following conventions usual for `/etc/hosts` (single IP,
+FQDN first and aliases as plain hostnames).
+
+## Gotchas
+
+This role uses the `hostnamectl` command installed by
+default on debian-like distros in order to ensure the
+new hostname is immediately set without needing to reboot.
+

roles/hostname/defaults/main.yml

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+---
+
+hostname_extra_hosts: []
+

roles/hostname/tasks/main.yml

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+---
+
+- name: Set /etc/hostname to FQDN of the server
+  copy:
+    dest: /etc/hostname
+    owner: root
+    group: root
+    mode: 0644
+    content: |
+      {{ hostname_fqdn }}
+
+- name: Ensure /etc/hosts contains all hostnames and aliases of the server
+  blockinfile:
+    dest: /etc/hosts
+    owner: root
+    group: root
+    mode: 0644
+    content: |
+      {% for host in hostname_hosts %}
+      {{ host.ip }}	{{ host.fqdn }}		{{ host.alias | default([]) | join(" ") }}
+      {% endfor %}
+    marker: "# {MARK} ANSIBLE MANAGED BLOCK"
+
+- name: Set hostname via hostnamectl to avoid a reboot
+  command:
+    cmd: "hostnamectl set-hostname {{ hostname_fqdn }}"
+

roles/hostname/vars/main.yml

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+---
+
+hostname_localhost:
+  ip: 127.0.0.1
+  fqdn: "localhost.localdomain"
+  alias: [ "localhost" ]
+hostname_hosts: "{{ [ hostname_localhost ] + hostname_extra_hosts }}"