Nagios Support Forum

Restart the server.
systemctl restart nagios
Read the output.

shutdown -r now to restart
shutdown -h now to halt

This is basic linux.

Have you considered searching the internet on nagfluxperfdata?

Nagiosadmin can manage any dashboard.

The command has the macro (think variable) $USERx$ that's defined in the resources.cfg file.
The command provides a bit of abstraction/security between allowing a service running actual shell commands vs nagios commands. It's a bit confusing at first I know.

Probably a better way is to do things as NXI is set up as I explained above.

The nsclient password in XI is typically defined in resources.cfg. It needs to match the password probably defined in nsclient.ini if I recall.

If you can't be root you need to turn this over to someone who can be root. Otherwise this is pointless.
This is basic linux administration.
When someone with root access and admin experience can respond a meaningful reply might be forthcoming.

The root user is the root user. It's called root.
whoami

Are you the root user?
cd /tmp
du -sk ./* | sort -rn