TELEICU/Rollback strategy - Revision history

Admin: Fix Comparison table: convert Markdown pipe syntax to proper MediaWiki wikitable (via update-page on MediaWiki MCP Server)

2026-07-06T03:22:47Z

Fix Comparison table: convert Markdown pipe syntax to proper MediaWiki wikitable (via update-page on MediaWiki MCP Server)

← Older revision		Revision as of 08:52, 6 July 2026
Line 53:		Line 53:
	== Comparison ==		== Comparison ==

			{\| class="wikitable"
	\| Dimension \| Ansible \| NixOS \|
			\|-
	\|---\|---\|---\|
			! Dimension
⚫	~~\| Speed~~ \| Depends on pull interval ~~\| Instant (CLI) or at boot \|~~
			! Ansible
⚫	~~\| Completeness \| Idempotency-dependent~~ \| Full — complete generation restore \|
			! NixOS
⚫	~~\| Offline rollback \| Not possible (needs git access)~~ \| Yes — generation is in local store \|
			\|-
⚫	~~\| Granularity~~ \| Per-playbook or per-role ~~\| Full OS generation \|~~
			\| Speed
⚫	~~\| Safety \| Can leave partial state~~ \| Atomic — all-or-nothing \|
		⚫	\| Depends on pull interval
			\| Instant (CLI) or at boot
			\|-
			\| Completeness
			\| Idempotency-dependent
		⚫	\| Full — complete generation restore
			\|-
			\| Offline rollback
			\| Not possible (needs git access)
		⚫	\| Yes — generation is in local store
			\|-
			\| Granularity
		⚫	\| Per-playbook or per-role
			\| Full OS generation
			\|-
			\| Safety
			\| Can leave partial state
		⚫	\| Atomic — all-or-nothing
			\|}

	{{Navbox TELEICU}}		{{Navbox TELEICU}}

Admin: Fix 2 Mermaid diagrams: remove

 wrapping (via update-page on MediaWiki MCP Server)

2026-07-06T03:22:09Z

Fix 2 Mermaid diagrams: remove <pre> wrapping (via update-page on MediaWiki MCP Server)

← Older revision		Revision as of 08:52, 6 July 2026
Line 10:		Line 10:
	== Path A: Ansible ==		== Path A: Ansible ==

	<pre>
	{{#mermaid:flowchart LR		{{#mermaid:flowchart LR
	COMMIT["git revert<br/>offending commit"]		COMMIT["git revert<br/>offending commit"]
Line 19:		Line 18:
	COMMIT --> PUSH --> PULL --> CONVERGE		COMMIT --> PUSH --> PULL --> CONVERGE
	}}		}}
	</pre>

	Procedure:		Procedure:
Line 33:		Line 31:
	== Path B: NixOS ==		== Path B: NixOS ==

	<pre>
	{{#mermaid:flowchart LR		{{#mermaid:flowchart LR
	subgraph Methods["Rollback Methods"]		subgraph Methods["Rollback Methods"]
Line 45:		Line 42:
	COMIN --> DONE		COMIN --> DONE
	}}		}}
	</pre>

	Procedure:		Procedure:

Admin: Automated edit (via update-page on MediaWiki MCP Server)

2026-07-06T03:10:44Z

Automated edit (via update-page on MediaWiki MCP Server)

← Older revision		Revision as of 08:40, 6 July 2026
Line 64:		Line 64:
	\| Granularity \| Per-playbook or per-role \| Full OS generation \|		\| Granularity \| Per-playbook or per-role \| Full OS generation \|
	\| Safety \| Can leave partial state \| Atomic — all-or-nothing \|		\| Safety \| Can leave partial state \| Atomic — all-or-nothing \|

			{{Navbox TELEICU}}

	{{Related}}		{{Related}}

Admin: Create TELEICU rollback strategy reference (via create-page on MediaWiki MCP Server)

2026-07-06T02:55:54Z

Create TELEICU rollback strategy reference (via create-page on MediaWiki MCP Server)

New page

{{Doc header
|type=reference
|domain=teleicu
|title=Rollback strategy
|order=21
}}

How changes are rolled back in both migration paths.

== Path A: Ansible ==

<pre>
{{#mermaid:flowchart LR
COMMIT["git revert offending commit"]
PUSH["Push to repo"]
PULL["ansible-pull picks up revert"]
CONVERGE["Nodes converge to previous state"]

COMMIT --> PUSH --> PULL --> CONVERGE
}}
</pre>

Procedure:

# Identify the offending commit(s) in the ansible repo
# <code>git revert <commit-hash></code>
# Push to the relevant branch
# Nodes apply on next ansible-pull run (default: 15-30 min timer)
# For urgent rollback: SSH into nodes and run <code>ansible-pull -U <repo></code> immediately

'''Limitation:''' If the change modified system state that is not idempotent, a simple revert may not fully restore. Ansible roles should be written idempotently.

== Path B: NixOS ==

<pre>
{{#mermaid:flowchart LR
subgraph Methods["Rollback Methods"]
CLI["nixos-rebuild switch --rollback (instant, from CLI)"]
BOOT["Boot menu (select prev generation at systemd-boot)"]
COMIN["comin rollback (point flake back to prior revision)"]
end

CLI --> DONE["Node returns to previous generation"]
BOOT --> DONE
COMIN --> DONE
}}
</pre>

Procedure:

* '''CLI rollback''': <code>nixos-rebuild switch --rollback</code> — switches to the previous generation immediately. No rebuild needed — the generation is already in the Nix store.
* '''Boot rollback''': Reboot and hold space during systemd-boot. Select the previous generation from the menu. Useful if the system is unbootable on the current generation.
* '''comin rollback''': Point the flake back to the previous revision in git. comin will pull and activate the older generation on next poll.

'''Key advantage:''' Every NixOS generation is atomic and bootable. Rollback is always available, even if the current generation is partially broken.

== Comparison ==

| Dimension | Ansible | NixOS |
|---|---|---|
| Speed | Depends on pull interval | Instant (CLI) or at boot |
| Completeness | Idempotency-dependent | Full — complete generation restore |
| Offline rollback | Not possible (needs git access) | Yes — generation is in local store |
| Granularity | Per-playbook or per-role | Full OS generation |
| Safety | Can leave partial state | Atomic — all-or-nothing |

{{Related}}