What causes "journald log monitoring only available on linux" in hashicorp/nomad?

Run the command on a Linux host with systemd/journald where the service actually exists.

journald log monitoring only available on linux

Error message

journald log monitoring only available on linux

What it means

NewExportMonitor in command/agent/monitor/export_monitor.go only supports journald-based log monitoring on Linux. If opts.ServiceName is non-empty (requesting journald log export) while runtime.GOOS is not linux, construction fails with this error. journald is a systemd/Linux facility so there is no implementation on other OSes.

Source

Thrown at command/agent/monitor/export_monitor.go:86

type ExportReader struct {
	io.Reader
	Cmd    *exec.Cmd
	UseCli bool
	Follow bool
}

// NewExportMonitor validates and prepares the appropriate reader before
// returning a new ExportMonitor or the appropriate error
func NewExportMonitor(opts MonitorExportOpts) (*ExportMonitor, error) {
	var (
		exportReader *ExportReader
		bufSize      int
	)

	if runtime.GOOS != "linux" &&
		opts.ServiceName != "" {
		return nil, errors.New("journald log monitoring only available on linux")
	}

	if opts.BufSize == 0 {
		bufSize = defaultBufSize
	} else {
		bufSize = opts.BufSize
	}

	if opts.OnDisk && opts.ServiceName == "" {
		e, prepErr := fileReader(opts)
		if prepErr != nil {
			return nil, prepErr
		}
		exportReader = e
	}

	if opts.ServiceName != "" && !opts.OnDisk {
		e, prepErr := cliReader(opts)

View on GitHub (pinned to 482b49bf1a)

Solutions

Run the command on a Linux host with systemd/journald where the service actually exists.
Remove the ServiceName option (or clear it) when monitoring is not needed on non-Linux platforms so journald monitoring is not requested.
Set the journald service name only via config applied to Linux clients, e.g. gate the config block by platform.
If on Linux this still fires, verify the build/runtime — it means runtime.GOOS reports non-linux, which should not occur on a standard Linux build.

Example fix

// before (on macOS)
NewExportMonitor(ExportMonitorOptions{ServiceName: "nomad-client.service", ...})
// after
if runtime.GOOS != "linux" {
    // drop journald option
    NewExportMonitor(ExportMonitorOptions{BufSize: 4096})
}

Defensive patterns

Strategy: validation

Validate before calling

if runtime.GOOS != "linux" && serviceName != "" {
    // skip or error before calling NewExportMonitor
    return errors.New("journald export requires linux; drop ServiceName or run on linux")
}

Try / catch

m, err := monitor.NewExportMonitor(opts)
if err != nil {
    if strings.Contains(err.Error(), "only available on linux") {
        log.Warn("journald monitoring unavailable on this OS; continuing without it")
        return nil
    }
    return err
}

Prevention

Only set ServiceName in configs deployed to Linux/systemd hosts.
Gate journald monitoring config by OS in provisioning tooling.
Run remote-monitoring commands on the Linux server, not a macOS workstation.

When it happens

Trigger: Requesting an export monitor with a ServiceName set (journald monitoring) on a Nomad agent/CLI running on darwin (macOS) or windows — e.g. running `nomad monitor`-style export with a systemd service name from a Mac.

Common situations: Developers running Nomad on macOS/Windows workstations issuing commands configured for a Linux server; copy-pasted config referencing journald service names on non-systemd hosts; CI runners on non-Linux OS.

Understand the failure class

Background: "unsupported platform" / "not supported on this platform" errors: what they mean and how to fix them — this error's family across 47 libraries.

Related errors

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/cf853a8b7c636d18. Report an issue: GitHub.