Assuming that you already have your linux system configured to syslog to your NPM server, you can use the command line "logger" to send anything you want into syslog from a script.
What you would do is write a script on the linux box that looks like this:
- logger This is a message from a linux system
Here's the man page for logger: logger(1) - Linux manual page There are more options for logger.
Then on the NPM server, you can check if "This is a message from a linux system" appears in your syslog area.
If it doesn't appear there, then you may need to configure /etc/syslog.conf or /etc/rsyslog.conf to correctly send to your NPM server. Remember that syslog needs restarting on the linux box when you edit the config file.