k3s-io/k3s · error

Rootless is not supported on windows

Error message

Rootless is not supported on windows

What it means

k3s rootless package (pkg/rootless/rootless_windows.go): the Windows build of k3s ships a stub Rootless() that panics immediately, because rootless mode (user-namespace, slirp/netavark networking) is implemented only for Linux. Seeing this panic means the Windows binary executed code that should only run on Linux builds.

Source

Thrown at pkg/rootless/rootless_windows.go:4

package rootless

func Rootless(stateDir string, enableIPv6 bool) error {
	panic("Rootless is not supported on windows")
}

View on GitHub (pinned to 6ba341e396)

Solutions

1. Do not enable rootless mode on Windows: remove the --rootless flag / disable the rootless start path for windows builds
2. Guard the call site: only invoke Rootless when runtime.GOOS == 'linux' (or move it behind a linux build tag)
3. Run the rootless control plane on a Linux host or VM; Windows nodes should join an existing cluster as agents without rootless

Example fix

// before
if err := rootless.Rootless(stateDir, enableIPv6); err != nil {
    return err
}

// after
if runtime.GOOS != "linux" {
    return fmt.Errorf("rootless mode is only supported on linux, current GOOS: %s", runtime.GOOS)
}
if err := rootless.Rootless(stateDir, enableIPv6); err != nil {
    return err
}

if runtime.GOOS != "linux" {
    return fmt.Errorf("rootless mode requires linux; refusing on %s", runtime.GOOS)
}
return rootless.Rootless(stateDir, enableIPv6)

func supportsRootless() bool {
    return runtime.GOOS == "linux"
}

When it happens

Trigger: Compiling k3s for GOOS=windows and starting it with rootless enabled (the Rootless function invoked during startup); invoking pkg/rootless.Rootless from cross-platform tooling or tests that do not guard on runtime.GOOS.

Common situations: Experimental Windows k3s builds where a start path enables rootless; CI matrix builds running windows binaries against linux-only flags; code changes that call Rootless without a build-tag guard.

Related errors

• Rootless is not supported on windows
• delegated cgroup v2 controllers are required for rootless
• Failed to create image import watcher:
• failed to start etcd client
• failed to start wrangler controllers

AI-assisted analysis of k3s-io/k3s@6ba341e396 (2026-08-15). Data as JSON: /api/errors/1699b996a707b282. Report an issue: GitHub.