fix(flannel): default the interface to each host's default IPv4 interface (#689)

* fix(flannel): default the interface to each host's default IPv4 interface

- Replace the hardcoded flannel_iface: eth0 with a per-host default derived
  from ansible_facts.default_ipv4.interface
- KVM/cloud hosts that are not named eth0 (e.g. enp1s0, ens3) now resolve the
  interface automatically instead of failing the k3s_node_ip lookup
- Update the commented calico_iface / cilium_iface examples to match
- Co-authored-by: Fritz Dunkel <677609+FinalDoom@users.noreply.github.com>
- Fixes #621

* test(flannel): add regression test for per-host interface default

- Add a focused test that renders the sample inventory's flannel_iface
  expression against fake ansible facts
- Assert a non-eth0 host (enp1s0, ens3) resolves its own interface and that
  the expression defaults from ansible_facts.default_ipv4.interface
- Wire it as a local pre-commit hook (default-interface-test)

* test(molecule): assert nodes register a non-loopback InternalIP

- Add a flannel-scenario verify assertion that every node reports an
  InternalIP derived from its configured flannel_iface
- Guards against k3s binding to 127.0.0.1 instead of the cluster interface
- Complements the pre-commit default-interface test with an end-to-end check

.github/ISSUE_TEMPLATE.md

@@ -1,85 +0,0 @@
-
-<!-- It's a good idea to check this post first for general troubleshooting https://github.com/timothystewart6/k3s-ansible/discussions/19   -->
-
-<!--- Provide a general summary of the issue in the Title above -->
-
-## Expected Behavior
-
-<!--- Tell us what should happen -->
-
-## Current Behavior
-<!--- Tell us what happens instead of the expected behavior -->
-
-## Steps to Reproduce
-
-<!--- reproduce this bug. Include code to reproduce, if relevant -->
-
-1.
-2.
-3.
-4.
-
-## Context (variables)
-<!--- please include which OS, along with the variables used when running the playbook -->
-
-Operating system:
-
-Hardware:
-
-### Variables Used
-
-`all.yml`
-
-```yml
-k3s_version: ""
-ansible_user: NA
-systemd_dir: ""
-
-flannel_iface: ""
-
-#calico_iface: ""
-calico_ebpf: ""
-calico_cidr: ""
-calico_tag: ""
-
-apiserver_endpoint: ""
-
-k3s_token: "NA"
-
-extra_server_args: ""
-extra_agent_args: ""
-
-kube_vip_tag_version: ""
-
-kube_vip_cloud_provider_tag_version: ""
-kube_vip_lb_ip_range: ""
-
-metal_lb_speaker_tag_version: ""
-metal_lb_controller_tag_version: ""
-
-metal_lb_ip_range: ""
-```
-
-### Hosts
-
-`host.ini`
-
-```ini
-[master]
-IP.ADDRESS.ONE
-IP.ADDRESS.TWO
-IP.ADDRESS.THREE
-
-[node]
-IP.ADDRESS.FOUR
-IP.ADDRESS.FIVE
-
-[k3s_cluster:children]
-master
-node
-```
-
-## Possible Solution
-<!--- Not obligatory, but suggest a fix/reason for the bug, -->
-
-- [ ] I've checked the [General Troubleshooting Guide](https://github.com/timothystewart6/k3s-ansible/discussions/20)

.github/ISSUE_TEMPLATE/bug_report.yml

@@ -0,0 +1,102 @@
+---
+name: Bug report
+description: Report a reproducible problem with the playbooks, roles, or generated resources.
+title: "[Bug]: "
+labels:
+  - bug
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Thanks for reporting a problem. Search existing issues and review the troubleshooting link first.
+        Remove credentials, tokens, public IP addresses, and private hostnames from all fields and logs.
+
+  - type: checkboxes
+    id: prerequisites
+    attributes:
+      label: Prerequisites
+      options:
+        - label: I searched existing issues and discussions for this problem.
+          required: true
+        - label: I reviewed the troubleshooting guidance linked from the issue chooser.
+          required: true
+        - label: I removed secrets and identifying infrastructure details from this report.
+          required: true
+
+  - type: textarea
+    id: summary
+    attributes:
+      label: Problem summary
+      description: Describe what failed and its impact.
+      placeholder: A concise description of the problem and affected nodes or components.
+    validations:
+      required: true
+
+  - type: textarea
+    id: expected
+    attributes:
+      label: Expected behavior
+      description: What should have happened?
+    validations:
+      required: true
+
+  - type: textarea
+    id: reproduction
+    attributes:
+      label: Steps to reproduce
+      description: Provide the smallest reliable sequence that reproduces the issue.
+      placeholder: |
+        1. Configure ...
+        2. Run ...
+        3. Observe ...
+    validations:
+      required: true
+
+  - type: input
+    id: revision
+    attributes:
+      label: Repository revision
+      description: Release, tag, branch, or commit SHA used.
+      placeholder: v1.36.2+k3s1+tt1 or a commit SHA
+    validations:
+      required: true
+
+  - type: input
+    id: ansible-version
+    attributes:
+      label: Ansible version
+      description: Output of `ansible --version`, shortened to version and Python details.
+      placeholder: ansible-core 2.18.0, Python 3.12
+    validations:
+      required: true
+
+  - type: textarea
+    id: environment
+    attributes:
+      label: Environment
+      description: Include target OS and version, architecture, node counts, platform, and network provider.
+      placeholder: Debian 13, amd64, 3 control nodes and 2 agents, bare metal, Cilium
+    validations:
+      required: true
+
+  - type: textarea
+    id: configuration
+    attributes:
+      label: Relevant sanitized configuration
+      description: Include only variables and inventory groups needed to reproduce the problem.
+      render: yaml
+    validations:
+      required: true
+
+  - type: textarea
+    id: logs
+    attributes:
+      label: Relevant logs or task output
+      description: Include the failing task and surrounding output. Redact sensitive or identifying values.
+      render: shell
+
+  - type: textarea
+    id: context
+    attributes:
+      label: Additional context
+      description: Add attempted fixes, suspected causes, regressions, or other useful context.

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,9 @@
+---
+blank_issues_enabled: false
+contact_links:
+  - name: Troubleshooting and support
+    url: https://github.com/timothystewart6/k3s-ansible/discussions/20
+    about: Review common troubleshooting guidance and ask configuration or usage questions.
+  - name: General discussions
+    url: https://github.com/timothystewart6/k3s-ansible/discussions
+    about: Discuss ideas and questions that are not confirmed bugs or concrete feature requests.

.github/ISSUE_TEMPLATE/feature_request.yml

@@ -0,0 +1,55 @@
+---
+name: Feature request
+description: Propose a focused improvement to supported repository behavior.
+title: "[Feature]: "
+labels:
+  - enhancement
+body:
+  - type: markdown
+    attributes:
+      value: |
+        Describe the use case before proposing an implementation. Search existing issues and discussions first.
+
+  - type: checkboxes
+    id: prerequisites
+    attributes:
+      label: Prerequisites
+      options:
+        - label: I searched existing issues and discussions for this request.
+          required: true
+        - label: This request is about reusable project behavior, not support for one private environment.
+          required: true
+
+  - type: textarea
+    id: problem
+    attributes:
+      label: Problem or use case
+      description: What limitation exists, who encounters it, and why does it matter?
+    validations:
+      required: true
+
+  - type: textarea
+    id: proposal
+    attributes:
+      label: Proposed behavior
+      description: Describe the desired user-visible result. Include example variables or commands when useful.
+    validations:
+      required: true
+
+  - type: textarea
+    id: alternatives
+    attributes:
+      label: Alternatives considered
+      description: Describe workarounds or other designs and their tradeoffs.
+
+  - type: textarea
+    id: compatibility
+    attributes:
+      label: Compatibility and operational impact
+      description: Note affected operating systems, architectures, CNIs, existing clusters, or reset behavior.
+
+  - type: textarea
+    id: context
+    attributes:
+      label: Additional context
+      description: Add relevant upstream documentation, examples, or prior discussion.

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,15 +1,46 @@
-# Proposed Changes
+## Summary
-<!--- Provide a general summary of your changes -->
+
+<!-- Explain the problem and the resulting behavior. Keep implementation details in the sections below. -->
+
+## Changes
 
--
--
 -
 
-## Checklist
+## Related issues
 
-- [ ] Tested locally
+<!-- Use "Fixes #123" when this pull request should close an issue. Write "None" when not applicable. -->
-- [ ] Ran `site.yml` playbook
+
-- [ ] Ran `reset.yml` playbook
+## Testing
-- [ ] Did not add any unnecessary changes
+
-- [ ] Ran pre-commit install at least once before committing
+<!-- List exact commands, scenarios, and relevant manual checks. Do not check a box for a test that was not run. -->
-- [ ] 🚀
+
+- [ ] `pre-commit run --all-files`
+- [ ] Relevant Ansible syntax checks
+- [ ] Relevant focused regression tests
+- [ ] Relevant Molecule scenario
+- [ ] Provisioning tested against a non-production cluster
+- [ ] Reset behavior tested against a non-production cluster
+
+Not run, with reason:
+
+## Risk and compatibility
+
+<!-- Cover existing clusters, upgrades, networking, supported platforms, security, and rollback. Write "None" when a
+category is not affected. -->
+
+- Existing cluster or upgrade impact:
+- Networking or CNI impact:
+- Security impact:
+- Rollback plan:
+
+## Documentation
+
+<!-- Identify updated docs and sample configuration, or explain why no documentation change is needed. -->
+
+## Final checklist
+
+- [ ] The change is focused and contains no unrelated edits.
+- [ ] Tests cover new behavior or a regression, where applicable.
+- [ ] User-facing variables are documented in role defaults, sample inventory, and the README.
+- [ ] Logs, examples, and configuration contain no secrets or identifying infrastructure details.
+- [ ] Generated files and local environment files are not included.

.github/copilot-instructions.md

@@ -0,0 +1,6 @@
+# GitHub Copilot instructions
+
+Read and follow the repository's root-level `AGENTS.md` before proposing or making changes. It is the canonical guide
+for architecture, safety, implementation, validation, and documentation expectations.
+
+Do not duplicate repository guidance here. If instructions need to change, update `AGENTS.md`.

.github/scripts/test-default-interface.py

@@ -0,0 +1,90 @@
+#!/usr/bin/env python3
+"""Assert the sample inventory resolves the flannel interface per host.
+
+flannel_iface defaults to the host's default IPv4 interface rather than a
+hardcoded eth0. This test extracts the flannel_iface expression from the
+sample inventory and proves that a host whose primary interface is not named
+eth0 (e.g. enp1s0, ens3) resolves the interface from ansible facts.
+"""
+
+from __future__ import print_function
+
+import os
+import re
+import subprocess
+
+from jinja2 import Environment, StrictUndefined
+
+
+def repo_root():
+    return subprocess.check_output(
+        ["git", "rev-parse", "--show-toplevel"], text=True
+    ).strip()
+
+
+def fail(message):
+    raise SystemExit("default-interface test failed: " + message)
+
+
+class FakeAnsibleFacts(object):
+    """Stand-in for the per-host ``ansible_facts`` dict."""
+
+    def __init__(self, default_iface, iface_ip):
+        self._default = {"interface": default_iface, "address": iface_ip}
+        self._ifaces = {
+            default_iface: {"ipv4": {"address": iface_ip}},
+        }
+
+    @property
+    def default_ipv4(self):
+        return self._default
+
+    def __getitem__(self, key):
+        return self._ifaces[key]
+
+
+def read_all_yml(root):
+    path = os.path.join(root, "inventory", "sample", "group_vars", "all.yml")
+    with open(path, "r") as handle:
+        return handle.read()
+
+
+def extract_value(content, key):
+    # Match a quoted value assigned to the key, e.g. flannel_iface: "...".
+    match = re.search(r"^%s:\s*\"(.+)\"\s*$" % re.escape(key), content, re.M)
+    if not match:
+        fail("could not find %s in the sample inventory" % key)
+    return match.group(1)
+
+
+def resolve(env, expression, facts):
+    template = env.from_string(expression)
+    return template.render(ansible_facts=facts)
+
+
+def main():
+    root = repo_root()
+    content = read_all_yml(root)
+    env = Environment(undefined=StrictUndefined)
+
+    flannel_expr = extract_value(content, "flannel_iface")
+    if "default_ipv4.interface" not in flannel_expr:
+        fail("flannel_iface no longer defaults from ansible facts")
+
+    # A host whose primary interface is enp1s0 (the core #621 scenario).
+    facts = FakeAnsibleFacts("enp1s0", "192.168.30.11")
+    resolved = resolve(env, flannel_expr, facts)
+    if resolved != "enp1s0":
+        fail("flannel_iface resolved to %r, expected enp1s0" % resolved)
+
+    # A different host with a different interface must resolve independently.
+    facts2 = FakeAnsibleFacts("ens3", "192.168.30.12")
+    resolved2 = resolve(env, flannel_expr, facts2)
+    if resolved2 != "ens3":
+        fail("flannel_iface resolved to %r, expected ens3" % resolved2)
+
+    print("default-interface regression test passed")
+
+
+if __name__ == "__main__":
+    main()

.github/workflows/ci.yml

@@ -14,6 +14,7 @@ on:
       - '**/FUNDING.yml'
       - '**/host.ini'
       - '**/*.md'
+      - '.github/ISSUE_TEMPLATE/**'
       - '**/.editorconfig'
       - '**/ansible.example.cfg'
       - '**/deploy.sh'

.pre-commit-config.yaml

@@ -84,3 +84,11 @@ repos:
         language: system
         pass_filenames: false
         files: ^roles/k3s_server/tasks/metallb\.yml$|^\.github/scripts/test-metallb-remote-read\.sh$
+      - id: default-interface-test
+        name: default interface test
+        entry: python3 .github/scripts/test-default-interface.py
+        language: python
+        additional_dependencies:
+          - Jinja2>=3.1
+        pass_filenames: false
+        files: ^inventory/sample/group_vars/all\.yml$|^\.github/scripts/test-default-interface\.py$

AGENTS.md

@@ -0,0 +1,130 @@
+# Agent Guide
+
+This file is the canonical repository guide for coding agents and automated contributors. Read it before making
+changes. Human contributors should also review [CONTRIBUTING.md](CONTRIBUTING.md).
+
+## Project overview
+
+This repository is an Ansible collection that provisions and resets highly available k3s clusters. It supports
+multiple networking choices, including Flannel, Calico, Cilium, kube-vip, and MetalLB.
+
+The main entry points are:
+
+- `site.yml`: provision or update a cluster.
+- `reset.yml`: remove k3s from a cluster.
+- `reboot.yml`: reboot cluster nodes.
+- `inventory/sample/`: example inventory and variables.
+- `roles/`: reusable Ansible roles used by the playbooks.
+- `molecule/`: integration scenarios run by CI.
+- `.github/scripts/`: CI support scripts and focused regression tests.
+
+## Source of truth
+
+- Role defaults belong in `roles/<role>/defaults/main.yml`.
+- Tasks belong in `roles/<role>/tasks/` and handlers in `roles/<role>/handlers/`.
+- Example user configuration belongs in `inventory/sample/`.
+- User-facing setup and variable documentation belongs in `README.md`.
+- Contributor workflows and review expectations belong in `CONTRIBUTING.md`.
+- Agent-specific repository instructions belong in this file.
+
+Keep `CLAUDE.md` and `.github/copilot-instructions.md` as small pointers to this file. Do not duplicate these
+instructions in tool-specific files.
+
+## Development setup
+
+Use a Python virtual environment. Do not commit the environment, generated logs, inventories, kubeconfigs, or
+credentials.
+
+```bash
+python3 -m venv .env
+source .env/bin/activate
+python3 -m pip install -r requirements.txt
+ansible-galaxy collection install -r collections/requirements.yml
+pre-commit install
+```
+
+`ansible.cfg` is intentionally ignored. Copy `ansible.example.cfg` when local configuration is needed.
+
+## Working rules
+
+1. Inspect the current branch and worktree before editing. Preserve unrelated user changes.
+2. Keep changes focused. Avoid drive-by formatting or dependency updates.
+3. Never add real IP addresses, hostnames, tokens, private keys, kubeconfigs, or inventory secrets.
+4. Use placeholders in examples and redact sensitive values from logs and issue reports.
+5. Preserve idempotence. An already-converged host should not report changes without a real state transition.
+6. Prefer Ansible modules over `ansible.builtin.command` or `ansible.builtin.shell`. When a command is required,
+   define accurate `changed_when` and `failed_when` behavior.
+7. Use fully qualified collection names, such as `ansible.builtin.copy`.
+8. Put configurable values in role defaults or inventory variables. Avoid embedding environment-specific values in
+   tasks and templates.
+9. Maintain compatibility with the operating systems and architectures listed in `README.md`.
+10. Do not weaken lint rules, tests, or CI checks to make a change pass.
+
+## Change guidance
+
+### Ansible tasks and roles
+
+- Use descriptive task names in sentence case.
+- Use YAML booleans (`true` and `false`) rather than aliases.
+- Quote file modes, for example `mode: "0644"`.
+- Notify handlers only when the managed resource changes.
+- Use `become: true` only where privilege escalation is needed.
+- Update role defaults, sample inventory, and the README together when adding or renaming user-facing variables.
+- Check reset behavior when provisioning introduces persistent services, files, mounts, or network state.
+
+### Templates and manifests
+
+- Keep Jinja logic small and readable. Move complicated decisions into task variables where practical.
+- Render valid YAML after Jinja evaluation.
+- Preserve explicit handling for optional and undefined variables.
+- Add or update a focused test under `.github/scripts/` when changing generated Kubernetes manifests or bootstrap
+  behavior.
+
+### Molecule scenarios
+
+- Reuse `molecule/resources/` for shared behavior.
+- Put scenario-specific inputs in `molecule/<scenario>/overrides.yml` and `verify-vars.yml`.
+- Update `molecule/README.md` when adding, removing, or materially changing a scenario.
+- Clean up resources created by tests, including failure paths.
+
+## Validation
+
+Run the smallest relevant checks while iterating, then run the complete local validation before considering a change
+ready:
+
+```bash
+pre-commit run --all-files
+```
+
+For playbook or role changes, also run syntax checks with a non-sensitive inventory:
+
+```bash
+ansible-playbook site.yml --syntax-check -i inventory/sample/hosts.ini
+ansible-playbook reset.yml --syntax-check -i inventory/sample/hosts.ini
+```
+
+Run focused regression scripts when their related files change. The mapping is defined in
+`.pre-commit-config.yaml`.
+
+Molecule tests require Vagrant, VirtualBox, host-only networking, and substantial local resources. Run the most
+relevant scenario when that environment is available:
+
+```bash
+molecule test --scenario-name <scenario>
+```
+
+If a required test can't be run locally, state exactly which check was skipped and why. Never claim a check passed
+unless it was executed.
+
+## Documentation and review
+
+- Keep commands copyable and examples free of secrets.
+- Update documentation in the same change as user-visible behavior.
+- Explain behavior changes, compatibility concerns, operational risks, and rollback steps in the pull request.
+- Use conventional commit messages with a scope, for example `fix(k3s-server): handle an existing token safely`.
+- Do not commit, push, open a pull request, or modify remote resources unless the user explicitly requests it.
+
+## Definition of done
+
+A change is ready for review when it is focused, documented, linted, tested in proportion to its risk, and shown in a
+clean diff with no secrets or generated artifacts.

CLAUDE.md

@@ -0,0 +1,3 @@
+@AGENTS.md
+
+`AGENTS.md` is the canonical repository guide. Follow it for all work in this repository.

CONTRIBUTING.md

@@ -0,0 +1,94 @@
+# Contributing to k3s-ansible
+
+Thank you for improving k3s-ansible. Contributions should be focused, safe to apply to existing clusters, and tested
+in proportion to their operational impact.
+
+## Before opening an issue
+
+- Search existing issues and discussions for the same behavior.
+- Review the [troubleshooting discussion](https://github.com/timothystewart6/k3s-ansible/discussions/20).
+- Remove tokens, credentials, public IP addresses, private hostnames, and other sensitive values from logs and
+  configuration.
+- For support requests, include the k3s-ansible revision, Ansible version, target operating system, architecture,
+  network provider, relevant sanitized variables, and a minimal reproduction.
+
+Use the bug report template for reproducible defects and the feature request template for proposed behavior.
+
+## Development environment
+
+Fork and clone the repository, then create a branch from the latest `master`:
+
+```bash
+git switch master
+git pull --ff-only
+git switch -c <type>/<short-description>
+```
+
+Create a Python environment and install the pinned development dependencies:
+
+```bash
+python3 -m venv .env
+source .env/bin/activate
+python3 -m pip install -r requirements.txt
+ansible-galaxy collection install -r collections/requirements.yml
+pre-commit install
+```
+
+Copy `ansible.example.cfg` to the ignored `ansible.cfg` file if local Ansible configuration is needed. Start custom
+inventories from `inventory/sample/`, keep them out of Git, and never use production credentials in tests.
+
+## Making changes
+
+- Keep each pull request focused on one problem or feature.
+- Follow [AGENTS.md](AGENTS.md) for repository structure, implementation conventions, and safety requirements.
+- Preserve idempotence and existing-cluster compatibility.
+- Add or update tests for behavior changes and regressions.
+- Update role defaults, sample inventory, and documentation when user-facing variables change.
+- Consider both provisioning and reset behavior for persistent resources.
+- Avoid unrelated reformatting and generated files.
+
+## Validation
+
+Run all pre-commit checks before submitting a pull request:
+
+```bash
+pre-commit run --all-files
+```
+
+For playbook or role changes, run syntax checks:
+
+```bash
+ansible-playbook site.yml --syntax-check -i inventory/sample/hosts.ini
+ansible-playbook reset.yml --syntax-check -i inventory/sample/hosts.ini
+```
+
+Run the most relevant Molecule scenario when Vagrant, VirtualBox, and the required host networking are available:
+
+```bash
+molecule test --scenario-name <scenario>
+```
+
+See [molecule/README.md](molecule/README.md) for scenario details and local requirements. Pull requests should list
+every check that was run and clearly identify checks that could not be run locally.
+
+## Commits and pull requests
+
+Use a conventional commit subject with a scope:
+
+```text
+type(scope): short description
+```
+
+Common types are `feat`, `fix`, `refactor`, `test`, `docs`, and `chore`. Write subjects in the imperative mood and
+keep commits logically focused.
+
+Pull requests should:
+
+- Describe the problem and the resulting behavior.
+- Identify compatibility, security, networking, and upgrade risks.
+- Include testing evidence without sensitive data.
+- Call out documentation and sample configuration changes.
+- Link related issues with `Fixes #<issue>` when applicable.
+- Avoid checking boxes for tests that were not run.
+
+Maintainers may ask for a change to be split when unrelated work makes it difficult to review or roll back.

README.md

@@ -2,51 +2,66 @@
 
 ![Fully Automated K3S etcd High Availability Install](https://img.youtube.com/vi/CbkEWcUZ7zM/0.jpg)
 
-This playbook will build an HA Kubernetes cluster with `k3s`, `kube-vip` and MetalLB via `ansible`.
+This Ansible collection builds a highly available Kubernetes cluster with k3s. It supports kube-vip for the control
+plane virtual IP, multiple CNI options, and either MetalLB or kube-vip for service load balancing.
 
 This is based on the work from [this fork](https://github.com/212850a/k3s-ansible) which is based on the work from [k3s-io/k3s-ansible](https://github.com/k3s-io/k3s-ansible). It uses [kube-vip](https://kube-vip.io/) to create a load balancer for control plane, and [metal-lb](https://metallb.universe.tf/installation/) for its service `LoadBalancer`.
 
-If you want more context on how this works, see:
+For more context on how it works, see:
 
 📄 [Documentation](https://technotim.com/posts/k3s-etcd-ansible/) (including example commands)
 
 📺 [Watch the Video](https://www.youtube.com/watch?v=CbkEWcUZ7zM)
 
+## Project guides
+
+- [Getting started](#-getting-started)
+- [Configuration variables](#variables)
+- [Upgrading an existing cluster](#-upgrading-an-existing-cluster)
+- [Local Molecule testing](molecule/README.md)
+- [Contributing guidelines](CONTRIBUTING.md)
+- [Repository guide for coding agents](AGENTS.md)
+
 ## 📖 k3s Ansible Playbook
 
-Build a Kubernetes cluster using Ansible with k3s. The goal is easily install a HA Kubernetes cluster on machines running:
+Build a Kubernetes cluster using Ansible and k3s. The goal is to make a highly available cluster straightforward to
+install on machines running:
 
 - [x] Debian (tested on version 13)
 - [x] Ubuntu (tested on version 26.04 LTS)
 - [x] Rocky (tested on version 10)
 
-on processor architecture:
+Supported processor architectures are:
 
-- [X] x64
+- [x] x64
-- [X] arm64
+- [x] arm64
-- [X] armhf
+- [x] armhf
 
 ## ✅ System requirements
 
-- Control Node (the machine you are running `ansible` commands) must have Ansible 2.11+ If you need a quick primer on Ansible [you can check out my docs and setting up Ansible](https://technotim.com/posts/ansible-automation/).
+- The control node, which runs the Ansible commands, must have Ansible 2.11 or newer. For a quick primer, see
+  [setting up Ansible](https://technotim.com/posts/ansible-automation/).
 
-- You will also need to install collections that this playbook uses by running `ansible-galaxy collection install -r ./collections/requirements.yml` (important❗)
+- Install the required collections with
+  `ansible-galaxy collection install -r ./collections/requirements.yml`.
 
 - [`netaddr` package](https://pypi.org/project/netaddr/) must be available to Ansible. If you have installed Ansible via apt, this is already taken care of. If you have installed Ansible via `pip`, make sure to install `netaddr` into the respective virtual environment.
 
-- `server` and `agent` nodes should have passwordless SSH access, if not you can supply arguments to provide credentials `--ask-pass --ask-become-pass` to each command.
+- Server and agent nodes should support passwordless SSH access. Otherwise, pass `--ask-pass --ask-become-pass` to
+  each playbook command.
 
 ## 🚀 Getting Started
 
 ### 🍴 Preparation
 
-First create a new directory based on the `sample` directory within the `inventory` directory:
+Create a cluster-specific inventory from the sample. The `inventory/` directory ignores custom inventory content so
+credentials and environment details aren't committed accidentally.
 
 ```bash
 cp -R inventory/sample inventory/my-cluster
 ```
 
-Second, edit `inventory/my-cluster/hosts.ini` to match the system information gathered above
+Edit `inventory/my-cluster/hosts.ini` to match the target hosts.
 
 For example:
 
@@ -67,9 +82,10 @@ node
 
 If multiple hosts are in the master group, the playbook will automatically set up k3s in [HA mode with etcd](https://rancher.com/docs/k3s/latest/en/installation/ha-embedded/).
 
-Finally, copy `ansible.example.cfg` to `ansible.cfg` and adapt the inventory path to match the files that you just created.
+Copy `ansible.example.cfg` to `ansible.cfg`, then update its inventory path. The local `ansible.cfg` file is ignored by
+Git.
 
-This requires at least k3s version `1.19.1` however the version is configurable by using the `k3s_version` variable.
+The minimum k3s version is `1.19.1`. Select the desired version with the `k3s_version` variable.
 
 If needed, you can also edit `inventory/my-cluster/group_vars/all.yml` to match your environment.
 
@@ -81,7 +97,8 @@ Start provisioning of the cluster using the following command:
 ansible-playbook site.yml -i inventory/my-cluster/hosts.ini
 ```
 
-After deployment control plane will be accessible via virtual ip-address which is defined in inventory/group_vars/all.yml as `apiserver_endpoint`
+After deployment, the control plane is accessible through the virtual IP defined by `apiserver_endpoint` in the
+inventory variables.
 
 ### 🔥 Remove k3s cluster
 
@@ -89,7 +106,7 @@ After deployment control plane will be accessible via virtual ip-address which i
 ansible-playbook reset.yml -i inventory/my-cluster/hosts.ini
 ```
 
->You should also reboot these nodes due to the VIP not being destroyed
+> Reboot the nodes after reset because the virtual IP may remain configured.
 
 ## 🔁 Upgrading an existing cluster
 
@@ -124,13 +141,21 @@ To copy your `kube config` locally so that you can access your **Kubernetes** cl
 ```bash
 scp debian@master_ip:/etc/rancher/k3s/k3s.yaml ~/.kube/config
 ```
-If you get file Permission denied, go into the node and temporarly run:
+If the copy fails with a permission error, grant the SSH user temporary read access using the least permissive method
+available for the target system. Restore the original ownership and permissions immediately after copying. Avoid
+world-writable permissions on the kubeconfig because it contains cluster credentials.
+
+For example, copy the file to a temporary user-readable path from the control node:
+
 ```bash
-sudo chmod 777 /etc/rancher/k3s/k3s.yaml
+ssh debian@master_ip 'sudo install -o "$(id -un)" -m 0600 /etc/rancher/k3s/k3s.yaml /tmp/k3s.yaml'
 ```
-Then copy with the scp command and reset the permissions back to:
+
+Copy `/tmp/k3s.yaml`, then remove the temporary remote copy:
+
 ```bash
-sudo chmod 600 /etc/rancher/k3s/k3s.yaml
+scp debian@master_ip:/tmp/k3s.yaml ~/.kube/config
+ssh debian@master_ip rm -f /tmp/k3s.yaml
 ```
 
 You'll then want to modify the config to point to master IP by running:
@@ -150,7 +175,7 @@ See the commands [here](https://technotim.com/posts/k3s-etcd-ansible/#testing-yo
 | `download` | `k3s_version` | string | ❌ | Required | K3s binaries version |
 | `k3s_agent`, `k3s_server`, `k3s_server_post` | `apiserver_endpoint` | string | ❌ | Required | Virtual ip-address configured on each master |
 | `k3s_agent` | `extra_agent_args` | string | `null` | Not required | Extra arguments for agents nodes |
-| `k3s_agent`, `k3s_server` | `group_name_master` | string | `null` | Not required | Name othe master group |
+| `k3s_agent`, `k3s_server` | `group_name_master` | string | `null` | Not required | Name of the master group |
 | `k3s_agent` | `k3s_token` | string | `null` | Not required | Token used to communicate between masters |
 | `k3s_agent`, `k3s_server` | `proxy_env` | dict | `null` | Not required | Internet proxy configurations |
 | `k3s_agent`, `k3s_server` | `proxy_env.HTTP_PROXY` | string | ❌ | Required | HTTP internet proxy |
@@ -227,9 +252,11 @@ It is run automatically in CI, but you can also run the tests locally.
 This might be helpful for quick feedback in a few cases.
 You can find more information about it [here](molecule/README.md).
 
-### Pre-commit Hooks
+### Pre-commit hooks
 
-This repo uses `pre-commit` and `pre-commit-hooks` to lint and fix common style and syntax errors.  Be sure to install python packages and then run `pre-commit install`.  For more information, see [pre-commit](https://pre-commit.com/)
+This repository uses `pre-commit` to check style, syntax, Ansible content, and shell scripts. Install the Python
+dependencies, run `pre-commit install` once, and run `pre-commit run --all-files` before submitting a change. See
+[CONTRIBUTING.md](CONTRIBUTING.md) for the complete development workflow.
 
 ## 🌌 Ansible Galaxy
 

inventory/sample/group_vars/all.yml

@@ -8,16 +8,18 @@ systemd_dir: /etc/systemd/system
 system_timezone: Your/Timezone
 
 # interface which will be used for flannel
-flannel_iface: eth0
+# Defaults to each host's default IPv4 interface (e.g. eth0, enp1s0, ens3)
+# so KVM/cloud hosts without eth0 work out of the box. Override per-host if needed.
+flannel_iface: "{{ ansible_facts.default_ipv4.interface }}"
 
 # uncomment calico_iface to use tigera operator/calico cni instead of flannel https://docs.tigera.io/calico/latest/about
-# calico_iface: "eth0"
+# calico_iface: "{{ ansible_facts.default_ipv4.interface }}"
 calico_ebpf: false # use eBPF dataplane instead of iptables
 calico_tag: v3.32.1 # calico version tag
 
 # uncomment cilium_iface to use cilium cni instead of flannel or calico
 # ensure v4.19.57, v5.1.16, v5.2.0 or more recent kernel
-# cilium_iface: "eth0"
+# cilium_iface: "{{ ansible_facts.default_ipv4.interface }}"
 cilium_mode: native # native when nodes are on the same subnet or use BGP, otherwise set tunnel
 cilium_tag: v1.20.0 # cilium version tag
 cilium_cli_tag: v0.19.7 # cilium cli version tag
@@ -47,7 +49,9 @@ kube_vip_bgp_as: "64513"  # Defines the AS for the BGP server
 kube_vip_bgp_peeraddress: "192.168.30.1"  # Defines the address for the BGP peer
 kube_vip_bgp_peeras: "64512"  # Defines the AS for the BGP peer
 
-# apiserver_endpoint is virtual ip-address which will be configured on each master
+# apiserver_endpoint is virtual ip-address which will be configured on each master.
+# This must be a free, routable IP on your network (not already assigned to a host
+# or service), and is used by kube-vip / MetalLB to expose the Kubernetes API.
 apiserver_endpoint: 192.168.30.222
 
 # k3s_token is required  masters can talk together securely

molecule/resources/verify_from_outside/tasks/test/verify-components.yml

@@ -38,6 +38,30 @@
           loop_control:
             label: "{{ item.metadata.name }} ready"
 
+        - name: Assert every node registered a node IP from its interface
+          # Each k3s node is launched with --node-ip derived from flannel_iface.
+          # Confirm every node carries a real InternalIP (not a loopback), which
+          # proves k3s bound to the cluster interface rather than defaulting to 127.0.0.1.
+          ansible.builtin.assert:
+            that: >-
+              (node_internal_ips | length) >= 1 and
+              (node_internal_ips | reject('eq', '127.0.0.1') | list | length) == node_internal_ips | length
+            success_msg: "{{ item.metadata.name }} is bound to {{ node_internal_ips | join(', ') }}"
+            fail_msg: >-
+              {{ item.metadata.name }} has no non-loopback InternalIP
+              (got: {{ node_internal_ips | join(', ') }})
+          vars:
+            node_internal_ips: >-
+              {{
+                (item.status.addresses | default([]))
+                | selectattr('type', 'equalto', 'InternalIP')
+                | map(attribute='address')
+                | list
+              }}
+          loop: "{{ verify_nodes.resources }}"
+          loop_control:
+            label: "{{ item.metadata.name }} InternalIP"
+
         - name: Get any Calico namespaces with Flannel enabled
           kubernetes.core.k8s_info:
             kind: Namespace
@@ -219,12 +243,26 @@
             namespace: metallb-system
             kubeconfig: "{{ kubecfg_path }}"
           register: metallb_info
+          until: metallb_info.resources | length > 0
+          retries: 15
+          delay: 10
           loop:
             - { kind: Deployment, name: controller }
             - { kind: DaemonSet, name: speaker }
           loop_control:
             label: "{{ item.kind }}/{{ item.name }}"
 
+        - name: Fail with a clear message if MetalLB resources are missing
+          ansible.builtin.fail:
+            msg: >-
+              Did not find {{ item.kind | lower }} {{ item.name }} in
+              metallb-system. Expected MetalLB to be deployed in this
+              scenario (verify_lb: {{ verify_lb }}).
+          when: item.resources | length == 0
+          loop: "{{ metallb_info.results }}"
+          loop_control:
+            label: "{{ item.item.kind }}/{{ item.item.name }}"
+
         - name: Assert MetalLB controller and speaker use the expected image tags
           ansible.builtin.assert:
             that:

roles/k3s_agent/templates/k3s.service.j2

@@ -11,7 +11,7 @@ ExecStartPre=-/sbin/modprobe overlay
 ExecStart=/usr/local/bin/k3s agent \
   --server https://{{ apiserver_endpoint | ansible.utils.ipwrap }}:6443 \
   {% if is_pxe_booted | default(false) %}--snapshotter native \
-  {% endif %}--token {{ hostvars[groups[group_name_master | default('master')][0]]['token'] | default(k3s_token) }} \
+  {% endif %}--token {{ hostvars[groups[group_name_master | default('master')][0]]['token'] | default(k3s_token) | replace( '%', '%%' ) }} \
   {{ extra_agent_args }}
 KillMode=process
 Delegate=yes

roles/k3s_server/defaults/main.yml

@@ -33,7 +33,7 @@ server_init_args: >-
     {% else %}
       --server https://{{ hostvars[groups[group_name_master | default('master')][0]].k3s_node_ip | split(",") | first | ansible.utils.ipwrap }}:6443
     {% endif %}
-    --token {{ k3s_token }}
+    --token {{ k3s_token | replace('%', '%%') }}
   {% endif %}
   {{ extra_server_args }}
 

roles/k3s_server/tasks/main.yml

@@ -27,7 +27,7 @@
 - name: Deploy metallb manifest
   ansible.builtin.include_tasks: metallb.yml
   tags: metallb
-  when: kube_vip_lb_ip_range is not defined and (not cilium_bgp or cilium_iface is not defined)
+  when: kube_vip_lb_ip_range is not defined and (cilium_bgp is not defined or cilium_iface is not defined)
 
 - name: Deploy kube-vip manifest
   ansible.builtin.include_tasks: kube-vip.yml

roles/k3s_server_post/tasks/main.yml

@@ -12,7 +12,7 @@
 - name: Deploy metallb pool
   ansible.builtin.include_tasks: metallb.yml
   tags: metallb
-  when: kube_vip_lb_ip_range is not defined and (not cilium_bgp or cilium_iface is not defined)
+  when: kube_vip_lb_ip_range is not defined and (cilium_bgp is not defined or cilium_iface is not defined)
 
 - name: Remove tmp directory used for manifests
   ansible.builtin.file:

roles/prereq/tasks/main.yml

@@ -33,6 +33,27 @@
     reload: true
   tags: sysctl
 
+- name: Check if br_netfilter module exists
+  ansible.builtin.shell: |
+    set -o pipefail
+    find /lib/modules/$(uname -r) -name "br_netfilter.ko*" | wc -l
+  args:
+    executable: /bin/bash
+  register: br_netfilter_exists
+  changed_when: false
+  when: ansible_os_family == "RedHat"
+  tags: sysctl
+
+- name: Install kernel-modules-extra if br_netfilter missing
+  ansible.builtin.yum:
+    name: kernel-modules-extra
+    state: present
+    update_cache: true
+  register: kernel_modules_installed
+  when:
+    - ansible_os_family == "RedHat"
+    - br_netfilter_exists.stdout | int == 0
+
 - name: Add br_netfilter to /etc/modules-load.d/
   ansible.builtin.copy:
     content: br_netfilter