In some cases administrators may need to remove the default file association to NoMachine for  .nxs and .nxv files, for example because they need to run by default another software associated to the same extensions.
 

How to remove the association between .nxs files and NoMachine

Run from a terminal and as root user:

xdg-mime uninstall --mode system NoMachine-mime.xml
 

How to remove the association between .nxv files and NoMachine

Create the NoMachine-mime.xml file with the following content:

<?xml version="1.0" encoding="UTF-8"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
    <mime-type type="application/nx-recording">
        <comment xml:lang="en">NoMachine recording</comment>
        <magic priority="50">
          <match value="&lt;!DOCTYPE NXPlayerRecording" type="string" offset="0"/>
        </magic>
        <glob pattern="*.nxv" />
        <generic-icon name="NoMachine-recording"/>
     </mime-type>
</mime-info>

and run from a terminal:

xdg-mime install --mode system NoMachine-mime.xml