+CAUTION: A node that is about to be added to the cluster cannot hold any guests.
+All existing configuration in `/etc/pve` is overwritten when joining a cluster,
+since guest IDs could otherwise conflict. As a workaround, you can create a
+backup of the guest (`vzdump`) and restore it under a different ID, after the
+node has been added to the cluster.
+
+Join Node to Cluster via GUI
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+[thumbnail="screenshot/gui-cluster-join-information.png"]
+
+Log in to the web interface on an existing cluster node. Under __Datacenter ->
+Cluster__, click the *Join Information* button at the top. Then, click on the
+button *Copy Information*. Alternatively, copy the string from the 'Information'
+field manually.
+
+[thumbnail="screenshot/gui-cluster-join.png"]
+
+Next, log in to the web interface on the node you want to add.
+Under __Datacenter -> Cluster__, click on *Join Cluster*. Fill in the
+'Information' field with the 'Join Information' text you copied earlier.
+Most settings required for joining the cluster will be filled out
+automatically. For security reasons, the cluster password has to be entered
+manually.
+
+NOTE: To enter all required data manually, you can disable the 'Assisted Join'
+checkbox.
+
+After clicking the *Join* button, the cluster join process will start
+immediately. After the node has joined the cluster, its current node certificate
+will be replaced by one signed from the cluster certificate authority (CA).
+This means that the current session will stop working after a few seconds. You
+then might need to force-reload the web interface and log in again with the
+cluster credentials.
+
+Now your node should be visible under __Datacenter -> Cluster__.
+
+Join Node to Cluster via Command Line
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Log in to the node you want to join into an existing cluster via `ssh`.