Saidar is a curses-based application to display system statistics.
The statistics include CPU, processes, load, memory, swap, network I/O and disks I/O.

Saidar uses the library libstatgrab. libstatgrab is a cross-platform library that provides access to statistics on the system that runs it.  The current list of statistics includes CPU usage, memory usage, disk usage, process counts, network traffic, disk I / O, and more.

Step1. Install Saidar on Debian Squeeze:

apt-get install saidar

Step2. Using saidar:

After having installed it, you can type in the command saidar:

root@css:~# saidar

For more info you can view the man page using the command : “man saidar”

DarkStat is a simple Packet Sniffing Network Bandwidth monitoring Tool forDebian and other Linux distributions. DarkStat gives simple web based output with nice graphs and statistics , it will automatically refreshed. Darkstat uses a very low footprint and the memory, CPU usage.

Step 1. Installation:

apt-get install darkstat

Step 2. How to use darkstat:

1. Running darkstat for eth0 :

darkstat -i eth0

NOTE: Now darkstat will start and run in background.

Step 3. View stats:

In your Browser type the address:

vnStat is a console-based network traffic monitor for Linux and BSD that keeps a log of network traffic for the selected interface(s). It uses the network interface statistics provided by the kernel as information source. This means that vnStat won’t actually be sniffing any traffic and also ensures light use of system resources.

Step 1. Installation:

apt-get install vnstat

Step 2. Select the interface you wish to monitor:

for eth0 :

vnstat -u -i eth0

Repeat this changing eth0 for each interface you wish to monitor.

NOTE: Once the text database have been initialised you’re ready to monitor your bandwidth usage. The package installs a cronjob which will update the database every five minutes.

Cacti is a complete network graphing solution designed to harness the power of RRDTool’s data storage and graphing functionality. Cacti provides a fast poller, advanced graph templating, multiple data acquisition methods, and user management features out of the box. All of this is wrapped in an intuitive, easy to use interface that makes sense for LAN-sized installations up to complex networks with hundreds of devices.

I’ll show you a simple script for easily monitor server

#!/bin/bash
# Monitoring Server with ping

########################################################

# host/ip
HOST="debian-tutorials.com"

# NO ping request
COUNT=3

# Report
SUBJECT="Server Down!"
EMAIL="admin@debian-tutorials.com"
for host in $HOST

do
count=$(ping -c $COUNT $HOST | grep 'received' | awk -F',' '{ print $2 }' | awk '{ print $1 }')

  if [ $COUNT -eq 0 ]; then
# Server is DOWN!

    echo "Host : $HOST is down (ping failed) at $(date)" | mail -s "$SUBJECT" $EMAILID
  fi
done