coredns/coredns · error

num sockets can not be zero or negative: %d

Error message

num sockets can not be zero or negative: %d

What it means

multisocket's parseNumSockets rejects socket counts below 1. The plugin binds one UDP/TCP socket per configured count, so zero or negative values are meaningless and are rejected with this error during Corefile setup.

Source

Thrown at plugin/multisocket/multisocket.go:47

	args := c.RemainingArgs()

	if len(args) > 1 || c.Next() {
		return c.ArgErr()
	}

	if len(args) == 0 {
		// Nothing specified; use default that is equal to GOMAXPROCS.
		config.NumSockets = runtime.GOMAXPROCS(0)
		return nil
	}

	numSockets, err := strconv.Atoi(args[0])
	if err != nil {
		return fmt.Errorf("invalid num sockets: %w", err)
	}
	if numSockets < 1 {
		return fmt.Errorf("num sockets can not be zero or negative: %d", numSockets)
	}
	if numSockets > maxNumSockets {
		return fmt.Errorf("num sockets exceeds maximum (%d): %d", maxNumSockets, numSockets)
	}
	config.NumSockets = numSockets

	return nil
}

View on GitHub (pinned to 558c9757a9)

Solutions

1. Set the directive to a positive integer, e.g. `multisocket 4`
2. Remove the multisocket directive if you want single-socket default behavior
3. Fix the template/script that generated the count so it clamps to at least 1

Example fix

// before
multisocket 0
// after
multisocket 1

n, err := strconv.Atoi(value); if err == nil && n < 1 { return errors.New("num sockets must be >= 1") }

if err := setup(...); err != nil && strings.Contains(err.Error(), "zero or negative") { /* clamp or remove directive */ }

When it happens

Trigger: Corefile directive like `multisocket 0` or `multisocket -2` is parsed by parseNumSockets (called from setup at plugin load).

Common situations: Attempting to 'disable' multisocket by setting 0 instead of removing the directive; templated configs computing a count from CPU metrics that yields 0.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

• reload duration value is expected
• at least one address or interface name is expected
• at least one address or interface must be given to except su
• cache TTL can not be zero or negative: %d
• prefetch amount should be positive: %d

AI-assisted analysis of coredns/coredns@558c9757a9 (2026-09-06). Data as JSON: /api/errors/f03d051a9fc5aa33. Report an issue: GitHub.