a report of the history of network usage.$ service vnstat status * vnStat daemon is runningRunning vnstat without any options would simply show the total amount of data transfer that took place since the date the daemon is running.$ vnstatDatabase updated: Mon Mar 17 15:26:59 2014 eth0 since 06/12/13 rx: 135.14 GiB tx: 35.76 GiB total: 170.90 GiB monthly rx | tx | total | avg. rate ------------------------+-------------+-------------+--------------- Feb '14 8.19 GiB | 2.08 GiB | 10.27 GiB | 35.60 kbit/s Mar '14 4.98 GiB | 1.52 GiB | 6.50 GiB | 37.93 kbit/s ------------------------+-------------+-------------+--------------- estimated 9.28 GiB | 2.83 GiB | 12.11 GiB | daily rx | tx | total | avg. rate ------------------------+-------------+-------------+--------------- yesterday 236.11 MiB | 98.61 MiB | 334.72 MiB | 31.74 kbit/s today 128.55 MiB | 41.00 MiB | 169.56 MiB | 24.97 kbit/s ------------------------+-------------+-------------+--------------- estimated 199 MiB | 63 MiB | 262 MiB |To monitor the bandwidth usage in realtime, use the '-l' option (live mode). It would then show the total bandwidth used by incoming and outgoing data, but in a very precise manner without any internal details about host connections or processes.$ vnstat -l -i eth0Monitoring eth0... (press CTRL-C to stop) rx: 12 kbit/s 10 p/s tx: 12 kbit/s 11 p/sVnstat is more like a tool to get historic reports of how much bandwidth is used everyday or over the past month. It is not strictly a tool for monitoring the network in real time.Vnstat supports many options, details about which can be found in the man page.Install vnstat# ubuntu or debian$ sudo apt-get install vnstat# fedora or centos (from epel)$ sudo yum install vnstat9. bwm-ngBwm-ng (Bandwidth Monitor Next Generation) is another very simple real time network load monitor that reports a summary of the speed at which data is being transferred in and out of all available network interfaces on the system.$ bwm-ngbwm-ng v0.6 (probing every 0.500s), press 'h' for help input: /proc/net/dev type: rate / iface Rx Tx Tot============================================================================ eth0: 0.53 KB/s 1.31 KB/s 1.84KB lo: 0.00 KB/s 0.00 KB/s 0.00KB---------------------------------------------------------------------------- total: 0.53 KB/s 1.31 KB/s 1.84KB/sIf the console size is sufficiently large, bwm-ng can also draw bar graphs for the traffic using the curses2 output mode.$ bwm-ng -o curses2Install Bwm-NG - On CentOS bwm-ng can be installed from Epel.# ubuntu or debian$ sudo apt-get install bwm-ng# fedora or centos (from epel)$ sudo apt-get install bwm-ng10. cbm - Color Bandwidth MeterA tiny little simple bandwidth monitor that displays the traffic volume through network interfaces. No further options, just the traffic stats are display and updated in realtime.$ sudo apt-get install cbm11. speedometerAnother small and simple tool that just draws out good looking graphs of incoming and outgoing traffic through a given interface.$ speedometer -r eth0 -t eth0Install speedometer# ubuntu or debian users$ sudo apt-get install speedometer12. PktstatPktstat displays all the active connections in real time, and the speed at which data is being transferred through them. It also displays the type of the connection, i.e. tcp or udp and also details about http requests if involved.$ sudo pktstat -i eth0 -nt$ sudo