netbirdio/netbird · error

change name %q -> %q: %w

Error message

change name %q -> %q: %w

What it means

rename() renames the freshly created interface with `ifconfig <old> name <new>` and wraps any non-zero exit. Typical kernel causes: the target name is already used by another interface, the new name exceeds the FreeBSD interface-name limit (IFNAMSIZ-1 = 15 characters), or the process lacks privileges.

Source

Thrown at client/iface/freebsd/link.go:152

		return "", fmt.Errorf("create %s interface: %w", groupName, err)
	}

	interfaceName, err := parseIFName(output)
	if err != nil {
		return "", fmt.Errorf("parse interface name: %w", err)
	}

	return interfaceName, nil
}

func (l *Link) rename(oldName, newName string) (string, error) {
	cmd := exec.Command("ifconfig", oldName, "name", newName)

	output, err := cmd.CombinedOutput()
	if err != nil {
		log.Debugf("ifconfig out: %s", output)

		return "", fmt.Errorf("change name %q -> %q: %w", oldName, newName, err)
	}

	interfaceName, err := parseIFName(output)
	if err != nil {
		return "", fmt.Errorf("parse new name: %w", err)
	}

	return interfaceName, nil
}

func (l *Link) del(name string) error {
	var stderr bytes.Buffer

	cmd := exec.Command("ifconfig", name, "destroy")
	cmd.Stderr = &stderr

	err := cmd.Run()
	if err != nil {

View on GitHub (pinned to 93e97f4bf1)

Solutions

1. Check the target name is free: `ifconfig <name>` should report 'does not exist'
2. Destroy the stale holder with `sudo ifconfig <name> destroy`, then retry netbird up
3. Keep the configured interface name at or under 15 characters
4. Run the agent as root

Example fix

# before
$ ifconfig wg0 name wt0
ifconfig: SIOCSIFNAME: File exists

# after
$ sudo ifconfig wt0 destroy
$ sudo ifconfig wg0 name wt0

if len(newName) > 15 {
    return fmt.Errorf("interface name %s exceeds FreeBSD IFNAMSIZ-1 (15 chars)", newName)
}
if _, err := freebsd.LinkByName(newName); err == nil {
    return fmt.Errorf("target interface name %s already exists", newName)
}

When it happens

Trigger: Add() after create() when the parsed name differs from the configured one; fails when l.name already exists, when the configured interface name is longer than 15 chars, or when run unprivileged.

Common situations: A leftover interface from a crashed run still holds the target name; custom interface name in configuration that is too long; two agents racing to take the same name.

Related errors

• up: %w
• link by name: %w
• link by name: %w
• parse new name: %w
• up %s interface: %w

AI-assisted analysis of netbirdio/netbird@93e97f4bf1 (2026-08-16). Data as JSON: /api/errors/cf4d24a49adc8290. Report an issue: GitHub.