.. jkm1552673113419
.. _configuring-ntp-servers-and-services-using-horizon:

================================================
Configure NTP Servers Using Horizon
================================================

You can add or update a list of external NTP servers for |prod| to use for
time and clock synchronization at any time after installation, using the
Horizon Web interface.

**NTP Service**

.. xbooklink For more information on configuring the NTP service for clock
   synchronization, see |node-doc|: `Host Inventory <hosts-tab>`.

.. note::
    |NTP| and |PTP| are configured per host. The default is |NTP|.

    Lock/unlock the host when updating **clock_synchronization** for the host.

**NTP Servers**

You can specify up to three |NTP| servers using Horizon or the CLI.

.. note::
    When you change the |NTP|/|PTP| system configuration you have to lock/unlock
    all hosts. This process requires a swact on the controllers. During a
    host swact the system may raise |NTP| alarms.

.. rubric:: |prereq|

Before making changes to the list of |NTP| servers, review the Fault Management
page and ensure that any existing system alarms are cleared.

.. caution::
    Before you can use fully qualified domain names (FQDN) instead of IPv4
    addresses, at least one valid DNS server is required. To add one, see
    :ref:`Specify DNS Servers Using Horizon <specifying-dns-servers-using-horizon>`.

.. rubric:: |proc|


.. _configuring-ntp-servers-and-services-using-horizon-steps-xfh-24z-5p:

#.  In the |prod| Horizon, open the System Configuration page.

    The System Configuration page is available
    from **Admin** \> **Platform** \> **System Configuration** in the left-hand pane.

#.  Select the NTP tab.

    The NTP page appears, showing the currently defined |NTP| servers.

    .. figure:: /shared/figures/system_configuration/jow1413850406811.png
        :scale: 100%

#.  Click **Edit NTP**.

#.  Add or edit the IP addresses or domain names, and then click **Save**.

#.  Click **Save**.

    This raises **250.001 Configuration out-of-date** alarms against the
    controllers, workers, and storages nodes. You can view the alarms on the
    Fault Management page.

#.  Lock and unlock the controllers, workers, and storage nodes to apply the
    configuration and clear the **Configuration out-of-date** alarms.

    Open the Host Inventory page, available
    from **Admin** \> **Platform** \> **Host Inventory** in the left-hand
    pane, and then select the **Hosts** tab. Hosts requiring attention are
    shown with the status **Config out-of-date**.

    To lock or unlock a host, click the **Action Menu** down arrow for the
    host and then use the menu selections.


    #.  Lock the standby controller.

        Wait for the lock operation to be completed.

    #.  Unlock the standby controller.

        Wait for the host to become available. Its configuration is
        updated, and its error message is cleared.

    #.  Perform a swact on the active controller.

        Click **Action Menu (down arrow)** \> **Swact Host** \>   for
        the active controller.

        Horizon Web interface access is interrupted, and the |prod| login
        screen appears. Wait briefly for the Web service to stabilize, and
        then log in again.

    #.  Lock the original controller (now in standby mode).

        Wait for the lock operation to be completed.

    #.  Unlock the original controller.

        Wait for it to become available. Its configuration is updated, and its
        error message is cleared.


#.  Ensure that the **Configuration out-of-date** alarms are cleared for
    both controllers.