fix(initsystem): don't let SysVinit match systemd hosts (#409)

[vikramhh]

Implements fix suggestion 2 from #409 — the maintainer-preferred direction (#409 (comment)).

Problem

In a mixed Linux+Windows cluster, rig could resolve SysVinit instead of Systemd for a systemd Linux host. SysVinit's probe test -d /etc/init.d succeeds on virtually every systemd distro (the directory is kept for LSB compatibility), so SysVinit matches systemd hosts. Because plumbing.Provider.Get moves a matching factory to the front of the shared registry (a homogeneity optimization), once a Windows host resolves — swapping WinSCM to the front and demoting Systemd behind SysVinit — a subsequently resolved systemd host matches SysVinit first. Service.IsRunning() then probes /etc/init.d/<svc> and returns false for a running systemd service, and Start/Stop/Restart/Enable/Disable target the wrong init system.

Fix

Make SysVinit detection specific: require systemd to be absent (stat /run/systemd/system fails) in addition to /etc/init.d existing, mirroring RegisterSystemd's probe. A systemd host now never resolves to SysVinit regardless of factory order — leaving the move-to-front optimization and the registration order untouched, as suggested in the issue.

Tests

• SysVinit not detected when systemd is present — SysVinit declines on a host where both /etc/init.d and systemd are present.
• Systemd wins on a systemd host after a Windows host resolved first (issue #409) — regression test that reproduces the mixed-cluster scenario using the default registry order.

The regression test fails on main (resolves to sysvinit) and passes with this change. go test ./initsystem/..., go vet, and gofmt are all clean.

Fixes #409

[vikramhh]

Heads-up: the failing schema-validation check is a pre-existing/flaky failure (go: updates to go.mod needed / go mod tidy), unrelated to this PR — it's also red on #402 and #403, and this change touches no imports or go.mod. All other checks (Lint, DCO, unit, integration-test-linux across alpine/debian12/ubuntu24.04, and windows) are green.

[Copilot]

Pull request overview

This PR fixes init-system detection so that SysVinit no longer matches systemd-based Linux hosts, preventing incorrect ServiceManager selection in mixed Windows+Linux environments where the provider’s move-to-front optimization can reorder factory precedence.

Changes:

• Tighten SysVinit detection by requiring /etc/init.d to exist and systemd to be absent (stat /run/systemd/system must fail).
• Add unit tests covering (1) SysVinit declining when systemd is present and (2) the mixed-cluster regression scenario from #409.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
initsystem/sysvinit.go	Makes SysVinit probing systemd-aware so it can’t shadow Systemd due to registry ordering.
initsystem/service_ops_test.go	Adds targeted detector + regression tests reproducing and preventing the mixed Windows/Linux misdetection.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.