certstestutil.WritePKIFiles(t, tmpdir, test.files)

			// executes create func
			ret, err := SharedCertificateExists(cfg)
			switch {
			case err != nil:
				if agg, ok := err.(utilerrors.Aggregate); ok && len(agg.Errors()) != test.expectedErrors {
					t.Errorf("SharedCertificateExists didn't fail with the expected number of errors, expected: %v, got: %v", test.expectedErrors, len(agg.Errors()))
				}

	}

	if !hasCertificateKey {
		// checks if the certificates are provided and are still valid, not expired yet.
		if ret, err := certs.SharedCertificateExists(initConfiguration); !ret {
			return err
		}
	}

	return nil

	uxName     string
}

// SharedCertificateExists verifies if the shared certificates exist and are still valid - the certificates must be
// equal across control-plane nodes: ca.key, ca.crt, sa.key, sa.pub, front-proxy-ca.key, front-proxy-ca.crt and etcd/ca.key, etcd/ca.crt if local/stacked etcd
// Missing private keys of CA are non-fatal and produce warnings.
func SharedCertificateExists(cfg *kubeadmapi.ClusterConfiguration) (bool, error) {