Design — MAISON-015: Linux runtime activation verification

Metadata

• Beads feature root: maison-mol-cg3x
• Feature slug: maison-015-linux-runtime-verification
• Design path: docs/src/features/maison-015-linux-runtime-verification/design.md
• Implemented record: docs/src/features/maison-015-linux-runtime-verification/index.md
• Base branch: dev
• Status: draft
• Review priority: P1

Feature Summary

Verify Linux runtime state after activation rather than only writing configuration files.

User Intent

Writing /etc/hostname does not necessarily update the active hostname; writing /etc/timezone does not establish /etc/localtime; SSH reload failures are suppressed.

Goals

• Post-activation checks verify active hostname, timezone, SSH configuration, and service unit state.
• Native system-manager options are used where possible.
• SSH reload failures are surfaced.

Non-Goals

• Replacing system-manager activation as the Linux system layer.
• Supporting Linux hosts without systemd; MAISON-015 supports systemd-backed Linux hosts only.

User-Facing Behavior

Operators keep using maison and mise tasks as the command surface. The feature changes the underlying safety, validation, or documentation contract named above without requiring operators to learn an unrelated tool. When behavior is unsafe or unsupported, Maison fails with an actionable message instead of silently continuing.

Requirements

Functional Requirements

• Linux activation requires systemd as the running init system and fails with an actionable diagnostic when systemd or systemctl is unavailable; no non-systemd fallback is supported.
• Use system-manager/native mechanisms for hostname, timezone, SSH config, and services where available.
• After activation, verify that hostname --static equals the configured host name and that the active timezone is America/New_York through systemd’s runtime state and /etc/localtime.
• Validate the active SSH configuration with sshd -t, reload or restart the active ssh.service or sshd.service, and fail activation when the check or reload fails; no SSH reload failure may be suppressed.
• Verify that system-manager.target and the Maison-managed prefill-authorized-keys.service reach an active state.
• Activation fails or reports a clear degraded state when runtime checks do not match intended configuration.
• Tests cover active hostname, /etc/localtime, SSH reload failure, and active service unit verification.

Quality Requirements

• Preserve Maison’s Nix/Lix system ownership and mise user ownership boundary.
• Prefer tested Python stdlib implementations for stateful behavior. Python task files under .mise/tasks/ are acceptable, including usage comments for argument validation and mise templating or sandboxing where useful.
• Do not introduce a Rust helper unless a later design proves Python cannot safely satisfy the filesystem or privilege boundary.
• Keep implementation small, reviewable, and covered by behavioral or fault-injection tests before relying on it.

Compatibility and Migration Requirements

• Preserve supported platforms: aarch64-darwin, aarch64-linux, and x86_64-linux.
• Preserve the absence of Home Manager.
• Update existing commands in place rather than introducing parallel legacy paths.
• Public Maison remains generic and public-safe; personal/site configuration belongs in a private overlay where relevant.

Existing Context

Maison currently documents a two-layer architecture where Nix/Lix owns privileged system state and mise owns user state. The review of commit ded7bbb745f34f1059930fc48eadafe267399ab2 identified this feature as required work. Existing reader documentation under docs/ describes the target operations and must be reconciled with delivered behavior.

Proposed Design

Extend nix/modules/linux/system.nix with one systemd-backed activation verification path. A pre-activation assertion requires a running systemd instance and systemctl; a host without that runtime fails before Maison replaces system files. Use system-manager’s Nix module mechanisms for the managed service units, source the managed timezone data into /etc/localtime while retaining the compatibility /etc/timezone file, and keep hostname configuration tied to the inventory host name.

The existing prefill-authorized-keys.service validates sshd -t and reloads or restarts the active SSH unit without suppressing failure. A dependent maison-runtime-verification.service runs after that service and verifies the active static hostname, systemd-reported timezone, /etc/localtime, system-manager.target, and prefill-authorized-keys.service. It exits non-zero with a field-specific diagnostic for any mismatch. The same system-manager activation service is used by local activation and deploy-rs remote activation; no separate deployment or non-systemd verification pipeline is introduced.

Architecture Consistency

Existing Patterns Reused

• Nix/Lix remains the privileged system layer.
• mise remains the user command and package/dotfile layer.
• maison check remains the repository-wide validation entrypoint.
• Python is the preferred home for stateful behavior that needs tests, parsing, locks, manifests, or recovery.

Invariants Preserved

• A file, package, service, or preference has exactly one owner.
• Intel macOS remains unsupported.
• Remote deployment remains split between deploy-rs system-profile handling and Maison repository/user handling.
• Public Maison does not contain private infrastructure identity or trusted access material.

New Decisions Introduced

• This feature adopts the concrete behavior described in Proposed Design as the supported Maison contract.

Architecture Documentation Changes

Update the architecture and operations pages named in Documentation Impact so current reader-facing docs match the implemented behavior.

Operational Considerations

Operators should receive explicit errors, recovery instructions, and validation evidence for this feature’s failure modes. Recovery docs must distinguish Nix generation behavior, repository/source behavior, user convergence behavior, and external package-manager side effects when those concerns apply.

Documentation Impact

Validation Strategy

• Nix/system-manager checks for generated activation verification and systemd-only assertions.
• Behavioral tests simulating hostname/timezone/SSH/service mismatch, missing systemd, and reload failure.
• mise -E dev run check and uv run scripts/check-docs.py.

Implementation Decomposition

• maison-015-linux-runtime-verification runtime-contract — Add Linux runtime verification tests.
• maison-015-linux-runtime-verification runtime-implementation — Implement Linux post-activation runtime checks.

Dependencies and Parallelism

This feature follows the Maison review order. Its implementation tasks depend on specification reconciliation. Sibling implementation tasks may run in parallel only when they do not edit the same command path, test file, or documentation page.

Rollout and Migration

Roll out by updating tests and docs first, then replacing the existing implementation path. Existing commands keep their names unless a feature explicitly narrows unsafe behavior.

Risks and Tradeoffs

• Safety fixes may temporarily reduce permissive behavior that previously appeared to work.
• Deployment and recovery changes require fault-injection coverage because ordinary happy-path tests are insufficient.
• Keeping shell and mise task compatibility while moving logic into Python may require small adapter changes.

Rejected Alternatives

• Broad rewrite before fixing the review findings.
• Preserving unsafe legacy paths as supported behavior.
• Storing private infrastructure identity in public Maison defaults.

Open Questions

None.

Deferred Decisions

None.

Planning Record

Questions Asked and Answers

• Stateful Maison behavior should move into tested Python implementations. .mise/tasks/ may contain Python task files and may use usage comments, task templating, and sandboxing.
• The default privileged deployment account is maison-deploy.
• Maison is the reusable vehicle; a tracked private overlay repository is the driver for personal/site configuration.
• Fresh setup supports --overlay <git-url-or-path>, prompts only when interactive, and fails clearly when a required overlay is missing in non-interactive mode.
• Public examples should be real workable starter configurations without personal infrastructure identity.

Assumptions

• The reviewed commit and review summary are authoritative planning evidence for this remediation roadmap.
• Feature branches should base on dev.

Design Changes During Planning

• The private inventory model changed from untracked local TOML to a tracked private overlay repository to preserve Maison’s durability and replication goals.

Source Material

• Maison review summary for commit ded7bbb745f34f1059930fc48eadafe267399ab2.
• Current Maison documentation under README.md and docs/.