What causes "no syslog host specified" in owasp-amass/amass?

Export SYSLOG_HOST to your syslog server, e.g. export SYSLOG_HOST=syslog.example.com

no syslog host specified

Error message

no syslog host specified

What it means

NewSyslogLogger builds a slog logger that ships JSON records to a syslog server. It reads SYSLOG_HOST, SYSLOG_PORT, and SYSLOG_TRANSPORT from the environment. This error is returned when SYSLOG_HOST is unset or empty, since a syslog destination cannot be dialed without a host.

Source

Thrown at internal/tools/log.go:61

			return nil, fmt.Errorf("failed to create the log directory: %v", err)
		}
	}

	f, err := os.OpenFile(filepath.Join(dir, logfile), os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		return nil, fmt.Errorf("failed to open the log file: %v", err)
	}

	return slog.New(slog.NewJSONHandler(f, nil)), nil
}

func NewSyslogLogger() (*slog.Logger, error) {
	port := os.Getenv("SYSLOG_PORT")
	host := strings.ToLower(os.Getenv("SYSLOG_HOST"))
	transport := strings.ToLower(os.Getenv("SYSLOG_TRANSPORT"))

	if host == "" {
		return nil, fmt.Errorf("no syslog host specified")
	}
	if port == "" {
		port = "514"
	}
	if transport == "" {
		transport = "udp"
	}

	writer, err := net.Dial(transport, net.JoinHostPort(host, port))
	if err != nil {
		return nil, fmt.Errorf("failed to create the connection to the log server: %v", err)
	}

	return slog.New(slogsyslog.Option{
		Level:     slog.LevelInfo,
		Converter: syslogConverter,
		Writer:    writer,
	}.NewSyslogHandler()), nil

View on GitHub (pinned to 79299dce87)

Solutions

Export SYSLOG_HOST to your syslog server, e.g. export SYSLOG_HOST=syslog.example.com
Add SYSLOG_HOST (and optionally SYSLOG_PORT, SYSLOG_TRANSPORT) to your deployment config (service unit, container env, k8s env)
Verify with `printenv SYSLOG_HOST` in the exact environment where the tool runs
Use file logging instead if no syslog server is available

Example fix

// before
cmd.Env = []string{"PATH=/usr/bin"} // SYSLOG_HOST missing
// after
cmd.Env = append(os.Environ(), "SYSLOG_HOST=syslog.example.com", "SYSLOG_PORT=514")

Defensive patterns

Strategy: validation

Validate before calling

host := os.Getenv("SYSLOG_HOST")
if host == "" {
	return errors.New("SYSLOG_HOST must be set when syslog logging is selected")
}

Try / catch

logger, err := tools.NewSyslogLogger()
if err != nil {
	if strings.Contains(err.Error(), "no syslog host specified") {
		log.Warn("SYSLOG_HOST unset; falling back to file logging")
		logger, err = tools.NewFileLogger(dir, logfile)
	}
	if err != nil { return err }
}

Prevention

Document SYSLOG_HOST as required whenever the syslog logger type is selected
Add the env var to service units, container env, and k8s manifests (not just interactive shells)
Fail fast at startup with a clear message if the env var is missing
Use a secrets/config management check (e.g. `printenv SYSLOG_HOST` in health checks)

When it happens

Trigger: Calling NewSyslogLogger when SYSLOG_HOST is not set in the environment (or set to an empty string), and the syslog logging path is selected via selectLogger.

Common situations: Deploying to a new container/Kubernetes pod where SYSLOG_HOST was configured only locally; selecting syslog logging in a config but never exporting the env vars; typo'd variable name (e.g. SYSLOGSERVER) or defining it only in an interactive shell but not in the service unit.

Understand the failure class

Background: "environment variable is not set" and "Missing keys in environment" errors: what missing required env var messages mean and how to fix them — this error's family across 28 libraries.

Related errors

AI-assisted analysis of owasp-amass/amass@79299dce87 (2026-09-06). Data as JSON: /api/errors/d7415d2f2e4d568d. Report an issue: GitHub.