Replacing license files, node.lic and server.lic on Linux doesn't require to terminate current sessions. 

This is the suggested procedure to replace license files:

1) Temporary disable user's access to NoMachine server by stopping it. Run from a terminal on the server host:

/usr/NX/bin/nxserver --stop

2) Create a backup of the original licenses: /usr/NX/etc/server.lic and /usr/NX/etc/node.lic

3) Copy the new licenses in place to /usr/NX/etc

4) Move to the /usr/NX/etc directory and  set correct permissions and ownership:

chown nx:root server.lic
chown nx:root node.lic
chmod 0400 server.lic
chmod 0400 server.lic

5) Start NoMachine server to accept new connections:

/usr/NX/bin/nxserver --start

In case of multi-node environments:

I) stop access to the node where it's necessary to replace the license file(s) by running in a terminal on the main server host:

/usr/NX/bin/nxserver --nodestop <node:port>

where <node:port> is the name of the remote node as it appears in the output of the 'nxserver --nodelist' command.

or stop access to the whole NoMachine subsystem by stopping the server as explained at point 1) above.

Then, in a terminal on the remote node:

II) Create a backup of the original license(s) placed in /usr/NX/etc/. Note that, depending on the product installed on the node, you may have: server.lic and node.lic or only node.lic. This is the case of the NoMachine Terminal Server Node.

III) Copy the new license(s) in place to /usr/NX/etc.

IV) Move to the /usr/NX/etc directory and  set correct permissions and ownership:

chown nx:root node.lic
chmod 0400 node.lic

and if it applies:

chown nx:root server.lic
chmod 0400 server.lic
 

IV) Restore access to this node by running in a terminal on the main server:

/usr/NX/bin/nxserver --nodestart <node:port>

or to the whole NoMachine subsystem if you have previously disabled it:

/usr/NX/bin/nxserver --start