installation: switch to YAML config files by default

[patrick-stephens]

See fluent/fluent-bit#9837, update to use YAML config by default.

I have not tackled providing YAML config for all installation options in the docs, this is mostly to cover the upgrade impact. Ideally @fluent/chronosphere-tech-writers we can also update all the legacy config in the docs to also have a YAML config example by default.

Summary by CodeRabbit

• Documentation
  • Added Fluent Bit v4.0+ upgrade notes explaining YAML configuration is now the default format. Includes platform-specific guidance for Linux (systemd override required), Windows, and macOS container deployments to ensure configuration compatibility.

[alexakreizinger]

made a few suggestions for clarity—although let me know if I misunderstood anything and made suggestions that don't make sense 😅

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds upgrade documentation for Fluent Bit v4.0+ explaining that configuration files now default to YAML format with .yaml extension, and provides platform-specific instructions for users who need to revert to legacy .conf configurations via systemd overrides on Linux or container defaults.

Changes

Fluent Bit v4.0+ Upgrade Notes

Layer / File(s)	Summary
Fluent Bit v4.0+ Configuration Format Upgrade Notes installation/upgrade-notes.md	New section documents the shift from .conf to .yaml configuration format default, with platform-specific guidance for Linux systemd units (-c <legacy config file>), Windows, and macOS container behaviors.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

🐰 A config in YAML, so clean and so bright,
The upgrade notes whisper: "Here's how to write!"
For Linux and Windows, containers galore,
We document paths that users adore. 📝✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the main change: documenting Fluent Bit's switch to YAML configuration files by default, which directly aligns with the upgrade note added to the documentation.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch 9714_switch_yaml_default_systemd

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@installation/upgrade-notes.md`:
- Around line 21-22: Remove the redundant "by default" from the sentence that
currently reads "Similarly, in Windows and macOS container environments, the
default launch command uses YAML configuration files by default." — change it to
"Similarly, in Windows and macOS container environments, the default launch
command uses YAML configuration files." Alternatively, if you want parallel
structure with the Linux guidance, rephrase to "Similarly, in Windows and macOS
container environments, use YAML configuration files for the default launch
command."

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 3dc17bbf-93a6-450b-ab44-17b60f1e2990

📥 Commits

Reviewing files that changed from the base of the PR and between c576098 and 91bd8cf.

📒 Files selected for processing (1)

• installation/upgrade-notes.md

[coderabbitai]

⚠️ Potential issue | 🟡 Minor | ⚡ Quick win

Remove redundant "by default".

The phrase "by default" appears twice in this sentence and is also redundant with line 14, which already establishes that YAML is the default format. This reduces clarity.

✏️ Proposed fix to remove redundancy

-Similarly, in Windows and macOS container environments, the default launch command uses YAML configuration files
-by default.
+Similarly, in Windows and macOS container environments, the default launch command uses YAML configuration files.

Or alternatively, for better parallel structure with the Linux guidance:

-Similarly, in Windows and macOS container environments, the default launch command uses YAML configuration files
-by default.
+In Windows and macOS container environments, the default launch command uses YAML configuration files.

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change

	Similarly, in Windows and macOS container environments, the default launch command uses YAML configuration files
	by default.
	Similarly, in Windows and macOS container environments, the default launch command uses YAML configuration files.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@installation/upgrade-notes.md` around lines 21 - 22, Remove the redundant "by
default" from the sentence that currently reads "Similarly, in Windows and macOS
container environments, the default launch command uses YAML configuration files
by default." — change it to "Similarly, in Windows and macOS container
environments, the default launch command uses YAML configuration files."
Alternatively, if you want parallel structure with the Linux guidance, rephrase
to "Similarly, in Windows and macOS container environments, use YAML
configuration files for the default launch command."