feat: Nodes page (#205)

Refs NethServer/dev#7506

Author: DavidePrincipi

cluster.rst

@@ -4,10 +4,8 @@
 Cluster management
 ==================
 
-A NethServer 8 cluster_ is composed of one **leader** node and multiple
-**worker** nodes.
-
-.. _cluster: https://en.wikipedia.org/wiki/Computer_cluster
+A NethServer 8 cluster [#clu]_ is composed of one **leader** node and
+multiple **worker** nodes.
 
 All nodes are managed through the Web user interface, which operates on
 the leader node.
@@ -27,8 +25,62 @@ by the VPN network size. However, it is advisable to add nodes gradually
 to avoid degrading the leader's performance due to increasing workload.
 
 
+.. _node-views:
+
+Node overview and details
+=========================
+
+The ``Nodes`` page displays an overview of the configured cluster nodes.
+Each card shows basic node attributes, the node alert counter, and node
+actions, which are explained in detail in the following sections.
+
+- Cluster nodes are uniquely identified by an increasing number. They are
+  named ``Node 1``, ``Node 2`` and so on. Use the ``Edit label`` action
+  from the three-dots menu to assign a custom name to the node. Note that
+  this label is only for UI visualization; see :ref:`set-fqdn` to change
+  the host name.
+
+- ``FQDN`` is the fully qualified host name (including the DNS domain
+  suffix) assigned to the node's operating system. It must meet the node
+  :ref:`DNS requirements <dns-reqs>`.
+
+- ``IP address`` is the main system address. It is the source address of
+  the default IP route, selected among the available system IP addresses.
+  To change basic network configuration refer to
+  :ref:`os-network-section`.
+
+- ``Applications`` is the number of applications installed on the node. It
+  is a link to the :ref:`Applications page <applications-section>`,
+  already filtered for the selected node.
+
+If there is an ongoing NethServer 7 migration procedure, a special node
+representing the NethServer 7 system is shown. All actions related to this
+node must be executed from the NethServer 7 migration tool available on
+that system. During migration, some cluster and application actions are
+inhibited. Refer to :ref:`migration-section` for more information.
+
+The :guilabel:`See details` button opens a detailed view of the selected
+node.
+
+- ``Applications`` and ``Network interfaces`` link to pages that provide
+  further details about the applications running on the node and the full
+  list of IP addresses.
+
+- ``VPN`` shows a summary of the node’s internal WireGuard network
+  parameters. The ``Endpoint`` value is important in case of :ref:`new
+  leader promotion <node-promotion-section>`. To change the WireGuard
+  listening port number, refer to :ref:`vpn-custom-section`.
+
+- The ``Alerts`` panel lists active node alerts, collected every minute.
+  See how to configure email notifications in :ref:`alerts-section`.
+
+- The following sections summarize CPU, load, memory, and disk usage.
+  Metrics are collected every minute, and averages are calculated over a
+  two-minute interval. For a detailed view of collected system metrics,
+  refer to :ref:`grafana_access-section`.
+
 Add a node
-==========
+----------
 
 You can add (join) a worker node to an existing cluster.
 The process consists of the following steps:
@@ -57,7 +109,7 @@ clicking the join button.
 When the node registration is complete, you can return to the leader user interface and install applications running on the new worker node.
 
 Remove a node
-=============
+-------------
 
 Worker nodes can be removed from the cluster. Before removing a given
 worker node, ensure no account provider replica is running on it. In the
@@ -87,7 +139,7 @@ off the node to finalize the node removal.
 .. _set-fqdn:
 
 Change FQDN
-===========
+-----------
 
 A node's FQDN is typically set during the post-installation steps. If it
 becomes necessary to change the FQDN later, follow these steps:
@@ -109,7 +161,7 @@ DNS as outlined in :ref:`dns-reqs`.
 .. _node-promotion-section:
 
 Promote a node to leader
-========================
+------------------------
 
 Adding and removing nodes may necessitate changing the cluster **leader
 node**.
@@ -141,7 +193,7 @@ node promotion.
 
 
 Reachable leader node
----------------------
+^^^^^^^^^^^^^^^^^^^^^
 
 If the current leader node is functioning properly, follow these steps:
 
@@ -161,7 +213,7 @@ promote the node` button becomes active, allowing you to complete the
 node promotion.
 
 Unreachable leader node
------------------------
+^^^^^^^^^^^^^^^^^^^^^^^
 
 If the current leader node is not reachable, run a command on any other
 worker node. Be prepared for this situation by enabling SSH, console, or
@@ -229,15 +281,22 @@ Available for both Android and iOS:
 Reset the cluster administrator password
 ----------------------------------------
 
-If you are locked out of the web user interface and you can still access a
-system command-line shell as ``root`` (e.g. by the system recovery console
-or SSH), run the following command to disable 2FA and reset the password:
+If you are locked out of the web user interface but can still access a
+system command-line shell as ``root`` (e.g. through the system recovery
+console or SSH), run the following command **on the leader node** to
+disable 2FA and reset the password:
 
 ::
 
   api-cli run alter-user --data '{"user":"admin","set":{"password":"Nethesis,1234","2fa":false}}'
 
-Replace the ``admin`` and ``Nethesis,1234`` default credentials as needed.
+Replace the ``admin`` username and ``Nethesis,1234`` password with the
+desired credentials.
+
+.. note::
+
+  The above command fails with ``AuthenticationError`` if executed on a
+  **worker node**. Run it only on the leader node.
 
 
 .. _audit-trail-section:
@@ -259,3 +318,7 @@ Audit trail events can be filtered by user, date, action type, and custom text m
     Audit trail information is stored in the leader node disk. In case of
     :ref:`new leader promotion <node-promotion-section>` the audit trail
     information in the old leader is no longer accessible.
+
+.. rubric:: Footnotes
+
+.. [#clu] https://en.wikipedia.org/wiki/Computer_cluster