hashicorp/nomad · error

failed to encode bootstrap command line: %w

Error message

failed to encode bootstrap command line: %w

What it means

After creating the debug command-line file, the hook writes the joined envoy bootstrap arguments via io.WriteString. If the write fails, it returns 'failed to encode bootstrap command line' wrapping the error. This is a debug-artifact write failure inside Prestart of the envoy bootstrap hook.

Source

Thrown at client/allocrunner/taskrunner/envoy_bootstrap_hook.go:324

		h.logger.Error("failed to generate envoy bootstrap config", "sidecar_for", service.Name)
		return fmt.Errorf("failed to generate envoy bootstrap config: %w", err)
	}
	h.logger.Debug("check for SI token for task", "task", req.Task.Name, "exists", siToken != "")

	proxyID := h.proxyServiceID(h.alloc.TaskGroup, service)
	bootstrap := h.newEnvoyBootstrapArgs(service, grpcAddr, envoyAdminBind, envoyReadyBind, siToken, bootstrapFilePath, proxyID)

	// Create command line arguments
	bootstrapArgs := bootstrap.args()

	// Write args to file for debugging
	argsFile, err := os.Create(bootstrapCmdPath)
	if err != nil {
		return fmt.Errorf("failed to write bootstrap command line: %w", err)
	}
	defer argsFile.Close()
	if _, err := io.WriteString(argsFile, strings.Join(bootstrapArgs, " ")+"\n"); err != nil {
		return fmt.Errorf("failed to encode bootstrap command line: %w", err)
	}

	// Create environment
	bootstrapEnv := bootstrap.env(h.groupEnv())

	// Write env to file for debugging
	envFile, err := os.Create(bootstrapEnvPath)
	if err != nil {
		return fmt.Errorf("failed to write bootstrap environment: %w", err)
	}
	defer envFile.Close()
	envEnc := json.NewEncoder(envFile)
	envEnc.SetIndent("", "    ")
	if err := envEnc.Encode(bootstrapEnv); err != nil {
		return fmt.Errorf("failed to encode bootstrap environment: %w", err)
	}

	// keep track of latest error returned from exec-ing consul envoy bootstrap

View on GitHub (pinned to 482b49bf1a)

Solutions

1. Check the wrapped I/O error for ENOSPC or EIO
2. Free disk space on the client volume
3. Confirm no other code path closes argsFile before this write
4. Retry the allocation after resolving storage issues

// check writability of the debug artifact target before writing
f, err := os.Create(bootstrapCmdPath)
if err != nil {
    return err
}
if err := f.Close(); err != nil {
    return err
}
os.Remove(bootstrapCmdPath)

if err := hook.Prestart(req); err != nil {
    if strings.Contains(err.Error(), "failed to encode bootstrap command line") {
        log.Printf("debug arg-file write failed (I/O): %v", err)
        // debug artifact failure; consider tolerating and continuing bootstrap
    }
}

When it happens

Trigger: io.WriteString(argsFile, strings.Join(bootstrapArgs, " ")+"\n") fails: the file descriptor is broken, disk fills mid-write, or the underlying write syscall returns an I/O error.

Common situations: Disk exhaustion during the write; file closed early due to an interleaved error path; rare I/O errors on the client's storage device.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• envoy must be used as connect sidecar or gateway
• failed to generate envoy bootstrap config: %w
• failed to write bootstrap command line: %w
• failed to write bootstrap environment: %w
• error creating bootstrap configuration for Connect proxy sid

AI-assisted analysis of hashicorp/nomad@482b49bf1a (2026-09-04). Data as JSON: /api/errors/1b53919d50eb91dc. Report an issue: GitHub.