henrygd/beszel · error

unexpected dest type for GetSystemdInfo: %T

Error message

unexpected dest type for GetSystemdInfo: %T

What it means

For legacy (0.18.0) responses with empty generic Data, unmarshalLegacyResponse copies resp.ServiceInfo into dest, which must be exactly *systemd.ServiceDetails. This error means dest was a different type, so the type assertion failed.

Source

Thrown at internal/hub/transport/transport.go:111

			if resp.SmartData == nil {
				return errors.New("no SMART data in response")
			}
			*d = resp.SmartData
			return nil
		case *smart.SmartDataResponse:
			if resp.SmartData == nil {
				return errors.New("no SMART data in response")
			}
			d.Data = resp.SmartData
			d.Complete = resp.SmartComplete
			return nil
		default:
			return fmt.Errorf("unexpected dest type for GetSmartData: %T", dest)
		}
	case common.GetSystemdInfo:
		d, ok := dest.(*systemd.ServiceDetails)
		if !ok {
			return fmt.Errorf("unexpected dest type for GetSystemdInfo: %T", dest)
		}
		if resp.ServiceInfo == nil {
			return errors.New("no systemd info in response")
		}
		*d = resp.ServiceInfo
		return nil
	}
	return fmt.Errorf("unsupported action: %d", action)
}

View on GitHub (pinned to b38fb7dafa)

Solutions

1. Pass *systemd.ServiceDetails as dest for GetSystemdInfo requests
2. Ensure you are not accidentally passing **systemd.ServiceDetails or the value type systemd.ServiceDetails
3. Upgrade agents to 0.19+ so the generic Data path is used instead of the legacy switch

Example fix

// before
var info systemd.ServiceList
err := t.Request(ctx, common.GetSystemdInfo, nil, &info)
// after
var info systemd.ServiceDetails
err := t.Request(ctx, common.GetSystemdInfo, nil, &info)

if _, ok := dest.(*systemd.ServiceDetails); !ok {
    return fmt.Errorf("GetSystemdInfo dest must be *systemd.ServiceDetails, got %T", dest)
}

func isSystemdDest(dest any) bool {
    _, ok := dest.(*systemd.ServiceDetails)
    return ok
}

if err := t.Request(ctx, common.GetSystemdInfo, nil, &details); err != nil {
    if strings.Contains(err.Error(), "unexpected dest type") { /* correct the dest type */ }
    return err
}

When it happens

Trigger: Calling Transport.Request/UnmarshalResponse with action common.GetSystemdInfo and a dest that is not *systemd.ServiceDetails, when the agent response carries no generic CBOR Data field.

Common situations: Passing a wrapper struct or value (non-pointer) type instead of *systemd.ServiceDetails; code written against the 0.19+ generic path running against an older agent.

Related errors

• unexpected dest type for GetSmartData: %T
• service name is required
• systemd manager unavailable
• unexpected dest type for GetData: %T
• unexpected dest type for CheckFingerprint: %T

AI-assisted analysis of henrygd/beszel@b38fb7dafa (2026-08-31). Data as JSON: /api/errors/b63a97b6cc8a1076. Report an issue: GitHub.