fix problem with host identification in /etc/hosts

[illmouse]

fix(hostname): correct hostname -f returning localhost on all supported OSes

Problem

The hostname role writes 127.0.0.1 localhost <hostname> to /etc/hosts.
glibc resolves hostname -f by returning the first alias on the 127.0.0.1
line whose aliases contain the short hostname — so it returns localhost,
not the actual hostname. Every cluster node reports its FQDN as localhost,
breaking software that keys on FQDN for node identity.

Affects all 7 supported distros (RedHat/CentOS/Rocky/Alma/Oracle ≥8, Ubuntu
≥22.04, Debian ≥11) — all glibc.

Fix

automation/roles/hostname/tasks/main.yml:

-        - { regexp: '^127\.0\.0\.1[ \t]+localhost', line: "127.0.0.1 localhost {{ ansible_hostname }}" }
+        - { regexp: '^127\.0\.0\.1\b', line: "127.0.0.1 {{ ansible_hostname }} localhost" }
1. Swap alias order — hostname is now the first alias, so hostname -f
returns the short hostname. localhost still resolves as the second alias.
2. Broaden regexp — ^127\.0\.0\.1\b replaces ^127\.0\.0\.1[ \t]+localhost.
The new line no longer matches the old regexp (it starts with
127.0.0.1 <hostname>, not 127.0.0.1 localhost), so without broadening
lineinfile would append a duplicate line on every run. \b prevents
matching 127.0.0.11.
Idempotency
Both edits ship together because they are coupled: the alias swap requires the
regexp broaden to stay idempotent (the new line must still match on the 2nd
converge, or lineinfile appends a duplicate → molecule idempotence action
fails).
Verification
- ansible-lint on automation/roles/hostname/ — 0 failures, 0 warnings
- make molecule-test (idempotence action catches duplicate-line regression)

[vitabaks]

Ok, thanks.