What is atop?
The program atop is an interactive monitor to view the load on a Linux system. It shows the occupation of the most critical hardware resources (from a performance point of view) on system level, i.e. cpu, memory, disk and network.
This brief tutorial is going to show you how to setup or configure a simple yet effective firewall rules for your systems. These rules also apply to Linux systems using iptables firewall. iptables is a simple firewall installed on most Linux systems by default. It’s used to allow or deny network communications in or out of a system.