Dominik Schön
5cf6a573f1
New patterns: - PAT-008: Ansible default_ipv6 fact missing on fresh VMs - PAT-009: Stale NBD devices after RBD volume swap Updated: - index.md: added PAT-008, PAT-009 - log.md: retrospective entry with 4 solution docs + 2 patterns - Solution docs dispatched to ~/docs/solutions/
60 lines
1.9 KiB
Markdown
60 lines
1.9 KiB
Markdown
---
|
|
pattern_id: PAT-008
|
|
title: "Ansible default_ipv6 fact missing on fresh VMs → lablabs.rke2 role fails"
|
|
category: tooling
|
|
severity: medium
|
|
status: active
|
|
first_observed: 2026-07-21
|
|
last_updated: 2026-08-30
|
|
related_systems: [rke2-kubernetes]
|
|
related_solution_docs:
|
|
- docs/solutions/bug-fixes/2026-07-21-ansible-rke2-default-ipv6-bug.md
|
|
related_skills: []
|
|
---
|
|
|
|
# Ansible default_ipv6 fact missing on fresh VMs → lablabs.rke2 role fails
|
|
|
|
## Symptom
|
|
|
|
The `lablabs.rke2` Ansible role fails on freshly provisioned VMs with a Jinja2 error:
|
|
```
|
|
ansible_facts['default_ipv6']['address']
|
|
```
|
|
The `default_ipv6` fact doesn't exist on VMs without IPv6 configured, causing the
|
|
`meta/argument_specs.yml` validation to crash.
|
|
|
|
## Root Cause
|
|
|
|
The `lablabs.rke2` role's `meta/argument_specs.yml` references
|
|
`ansible_facts['default_ipv6']['address']` with a hardcoded default. On fresh VMs
|
|
without IPv6, `ansible_facts['default_ipv6']` is undefined → Jinja2 raises
|
|
`UndefinedError`.
|
|
|
|
A `pre_task` setting `default_ipv6` via `combine()` doesn't help because the
|
|
argument_specs validation runs BEFORE pre_tasks — it re-collects facts and
|
|
overwrites the pre_task fix.
|
|
|
|
## Mitigation
|
|
|
|
Patch `meta/argument_specs.yml` directly in the role:
|
|
```yaml
|
|
# Replace:
|
|
default: "{{ ansible_facts['default_ipv6']['address'] }}"
|
|
# With:
|
|
default: "{{ ansible_facts.default_ipv6.address | default(None) }}"
|
|
```
|
|
|
|
Or: enable IPv6 on the target VMs (faster workaround, no role patching needed).
|
|
|
|
## Prevention
|
|
|
|
- Pin Ansible roles and patch argument_specs when they assume facts that may not exist
|
|
- Test roles on fresh VMs without IPv6 before production use
|
|
- Consider forking the role with the fix upstream
|
|
|
|
## Evidence
|
|
|
|
- Observed during GPU worker provisioning (worker-04/05, Jul 2026)
|
|
- Solution doc: `docs/solutions/bug-fixes/2026-07-21-ansible-rke2-default-ipv6-bug.md`
|
|
- Session: @session:default/20260721_115501_78b25032
|