Starting from version 5, any Unix-like workstation or server with an X Window System (i.e. a graphical user interface based on X) can be integrated into a NoMachine environment without the need for installing the NoMachine software on that host. This gives administrators the possibility to offer access to critical business “legacy”, applications whilst still providing an easy-to-use contemporary environment.

In a NoMachine server multi-node environment (v. 5) these Unix-like hosts are named Foreign nodes to distinguish them from NoMachine nodes. A NoMachine node has a NoMachine server or node package installed, for example a Terminal Server Node in the case of a Linux host. A foreign node is simply a host on which a NoMachine server or node package is not available. Adding such nodes to a NoMachine server can be done via User Interface (GUI) or via the command line.
 

Pre-requisites to integrate a Foreign node into a NoMachine multinode environment

Pre-requisites to integrate a Foreign node into a NoMachine multinode environment are:

Main differences between NoMachine and Foreign nodes

These are the main differences between NoMachine nodes and Foreign nodes:

a. Users can run virtual desktops (multiple individual instances of the node desktop)  on the NoMachine Linux nodes while only connections to the physical desktop are possible on Foreign nodes.
   
b. Virtual desktop sessions can be load-balanced by the server automatically among the NoMachine nodes. Sessions on Foreign nodes cannot be load-balanced.

c. Connections to NoMachine nodes can use the NX or the SSH protocol. Connections to Foreign nodes must use the SSH protocol.

d. NoMachine (Linux) nodes in load-balancing can be stopped and started, Foreign nodes cannot.

Adding a Foreign node to the NoMachine multinode environment

To add the foreign node, use the 'nxserver --nodeadd' command and specify the '--foreign' option on the NoMachine server host.

The basic format of the command is:

nxserver --nodeadd <node>  --foreign  

where  <node> is the IP or hostname of the Foreign node.

Connections to the Foreign node will use the SSH protocol on port 22. It's possible to provide the --port parameter to specify a different port, for example:

nxserver --nodeadd <node>  --port 2222 --foreign 
 

All the other parameters of the 'nxserver --nodeadd' command can be specified, except for:

 [--weight <weight>], available only for NoMachine nodes being part of the load-balancing mechanism

 [--limit <limit>], available only for NoMachine nodes supporting virtual desktops (this parameter allows to limit the number of virtual desktops allowed on the specified node).

The most common reasons why connections to the Foreign node are not  possible

Verify that all pre-requisites listed above are met.

Regarding the X server, consider that on some operating systems the X server is started with the '-nolisten tcp' . If this is the case, restart the X server after enabling TCP listening (please refer to the official documentation of your distribution).

Connections to the Foreign node are no longer possible when the fingerprint on the Foreign node is changed.

In this case, run on the NoMachine server host the following command, accept the new fingerprint and add it to the known_hosts file:

nxserver --nodeupdate <node:port> [--strict-host-key-checking yes|no]

References

For further commands to manage Foreign nodes, please refer to the NoMachine Enterprise Products 5.x - Server Administrator's Guide - Advanced Functions:

https://www.nomachine.com/DT07M00091

An illustrated tutorial is also available here: https://www.nomachine.com/adding-nodes-to-enterprise-and-cloud-server-via-the-gui

For NoMachine 4.x read here:

https://www.nomachine.com/AR01F00498