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First, install your GNU/Linux distribution. It is recommended to select a basic installation type with no extra stuff. That means no GNOME, KDE, "Server" packages, or anything else.
Linux Security Settings: SELinux and Firewalling
If you're running CentOS or any other Red Hat-derived distribution, be sure that SELinux is turned offwe recommend that you turn off SELinux. Permissive mode was tested and it worked well, just very nagging. So disabling ; the default mode is known to interfere with NMIS. Disabling SELinux is a lot easier that waythan performing the extensive configuration that SELinux needs.
Similarly, if you have a firewall on your server (e.g. iptables) you need to make sure that it accepts incoming HTTP (possibly HTTPS) connections, and SNMP traps and Syslog connections/packets. This involves TCP ports 80 and 443, and UDP ports 161, 162 and 514.
NMIS8 Installation
And speaking of NMIS, if you haven't already downloaded it, the latest version (v8.5.6G at time of this writing) is available at http://opmantek.com/.
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