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Cluster management

A NethServer 8 cluster is composed of one leader node and multiple worker nodes.

An NS8 cluster composed only of the leader node, is a fully functional system. Worker nodes can be added or removed at any time. NS8 clusters support a maximum of 4 nodes.

All nodes are managed by the Web user interface running on the leader node.

Add a node

You can add (join) a worker node to an existing cluster. The process consists of three steps:

  • install the new node
  • obtain the join code from the leader node
  • enter the join code into the worker node

First, prepare a machine with the same Linux distribution used for the leader node, then follow the :ref:`install instruction <install-section>` until the login to the Web user interface.

After the login on the worker node, click the :guilabel:`Join cluster` button.

Ensure the node Fully Qualified Domain Name (FQDN) is correct, and respects the :ref:`DNS requirements <dns-reqs>`.

On the leader node, access the Nodes page and click on :guilabel:`Add node to cluster` and copy the join code from the dialog box.

Return to the worker node and paste the code inside the Join code field and click the :guilabel:`Join cluster` button. If the leader node does not have a valid TLS certificate, remember to disable the TLS certification validation option before 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 Domains and users page, for each domain follow the N providers link to see the node where a provider replica is installed on, then remove it.

Warning

If the node is not reachable, or is not responding, the provider replica removal must be completed manually after the node removal.

Access the Nodes page, go to the three-dots menu of the node and click on Remove from cluster to open a confirmation window. Applications installed on the node are listed: review that list carefully because node removal is not recoverable.

If the node removal window is confirmed by pushing the :guilabel:`I understand, remove node` button, the node and its applications are disconnected, their authorizations are revoked and they cannot access the cluster any more.

When a node is removed from the cluster the applications running on it are not affected and they are left in a running state. Shutdown and switch off the node to finalize the node removal.

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:

  1. Access the Nodes page and navigate to the three-dots menu of the corresponding node card.
  2. Select the Set FQDN action.

If you are changing the leader node's FQDN, an additional validation procedure will check if the new FQDN is correctly resolved by all worker nodes.

If you are changing a worker node's FQDN, this validation is not enforced. However, it is still necessary to correctly register the new FQDN in the DNS as outlined in :ref:`dns-reqs`.

Promote a node to leader

Adding and removing nodes may necessitate changing the cluster leader node.

A suitable leader node must be reachable by all other worker nodes.

Every worker node must correctly resolve the leader's FQDN, which must be consistent across all worker nodes.

Depending on the state of the current leader node, there are two procedures to promote a node to the leader role:

  • Reachable leader node
  • Unreachable leader node

After promoting a leader, it is necessary to perform these additional tasks:

Additionally, refer to the note in :ref:`audit-trail-section` regarding node promotion.

Note

Promoting a new leader entails changes to the System logs configuration. For more details, refer to :ref:`logs-persistence-section`.

Reachable leader node

If the current leader node is functioning properly, follow these steps:

  1. Access the Nodes page.
  2. Open the three-dots menu of the node to promote and click on Promote to leader.

The Check node connectivity checkbox verifies the connection of the old leader with the designated one. Since the VPN connection cannot be probed, only an HTTPS connection is attempted. This may fail due to intervening network devices (e.g., NAT and port-forwarding setups). If you are certain that the configuration is correct, you can disable the check, but proceed at your own risk!

When the confirmation string is typed, the :guilabel:`I understand, 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 Cockpit terminal root access to the nodes.

For example, to promote the node with ID 3, run the following command on every worker node:

switch-leader --node 3

If the command fails because the VPN endpoint of node 3 is not defined or is incorrect, use the optional --endpoint parameter, for example:

switch-leader --node 3 --endpoint node3.example.net:55820

The VPN endpoint parameter consists of an address (name or IP) prefix and a UDP port number suffix, separated by a colon :.

Administrators

Cluster administrators can fully manage the cluster. It's recommended to create a personal user for each cluster administrator. All actions executed by a cluster administrator are collected inside a security :ref:`audit-trail-section`.

To add a new cluster administrator go to the Settings page and select the Cluster administrators card. Then click on :guilabel:`Create admin` button and fill the required fields.

An administrator can't delete its own user. To delete an administrator, you must log in with another existing cluster administrator.

Administrators can change their own password from the Account card inside the Settings page.

Two-factor authentication (2FA)

Two-factor authentication (2FA) can be used to add an extra layer of security required to access the cluster management user interface.

The administrator can enable 2FA from the Account card inside the Settings page by clicking the :guilabel:`Enable 2FA` button.

The user will have to:

  1. download and install the preferred 2FA application on the smartphone
  2. scan the QR code with the 2FA application
  3. generate a new code and copy it inside the verification field, then click :guilabel:`Verify code`

Smartphone applications

There are several commercial and open source 2FA applications:

Available for both Android and iOS:

  • FreeOTP: available for both Android and iOS
  • Authenticator: available on iOS only
  • 2FAS: 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:

api-cli run alter-user --data '{"user":"admin","set":{"password":"Nethesis,1234","2fa":false}}'

Replace the admin and Nethesis,1234 default credentials as needed.

Audit trail

Inside the audit trail page, cluster administrators can inspect all actions executed by any other administrator. Each event of the audit trail contains at least:

  • date and time of the action
  • user name of the cluster administrator
  • name of the action

Audit trail events can be filtered by user, date, action type, and custom text match.

Note

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.