The majority of server configuration keys don't require to restart server and/or services to apply different settings: changes will be effective at the new session startup and will not influence sessions already running.

In some cases however it's necessary to restart the NoMachine server and/or its services. Please note that restarting the server implies to terminate all the running sessions that will be no longer available for reconnection.

All configuration keys defining a service port (e.g. NXUPnPPort,UDPPort etc ..) require to restart at least the corresponding service: for example if you modify the NXPort you then need to restart the nxd service. In this case a full restart of the NoMachine server (nxserver --restart) is not mandatory but can be done as well.

All configuration keys to enable/disable the automatic start/stop of a service (e.g. StartNXDaemon) require instead to restart nxserver.

1) Server configuration keys requiring to restart the NoMachine server

Keys for server v. 4 or later

AvailableSessionTypes
ClientConnectionMethods
DisplayBase
DisplayLimit
EnableFirewallConfiguration
EnableNetworkBroadcast
EnableUPnP
HTTPUPnPPort
NetLogonDependency
NXUPnPPort
RunNodeMode
SSHAuthorizedKeys
SSHDUPnPPort
StartHTTPDaemon
StartNXDaemon
StartSSHDaemon
UDPPort
UpdateFrequency

Additional server keys available starting from v. 5

CreateDisplay
DisplayOwner
DisplayGeometry

2) Server configuration keys requiring to restart the correspondent NoMachine service

NXPort ->  nxserver --restart nxd

SSHDPort  -> nxserver --restart nxsshd (on Windows only)

Note for NoMachine servers supporting web sessions

In case you modified the HTTP/HTTPS ports for the NoMachine web server in the htd.cfg file, it's required to restart the nxhtd service:

nxserver --restart nxhtd