top of monitoring tools for SysAdmin

Taked from http://www.cyberciti.biz/tips/top-linux-monitoring-tools.html
1)vmstat - System Activity, Hardware and System Information
2)free - Memory Usage
3)iostat - Average CPU Load, Disk Activity
4)sar - Collect and Report System Activity
5)mpstat - Multiprocessor Usage
6)pmap - Process Memory Usage
7)netstat - Network Statistics
8)ss - Network Statistics too
9)iptraf - Real-time Network Statistics
10)/Proc file system - Various Kernel Statistics
# cat /proc/cpuinfo
# cat /proc/meminfo
# cat /proc/zoneinfo
# cat /proc/mounts
11)Nagios - Server And Network Monitoring
12)Cacti - Web-based Monitoring Tool
13)Gnome System Monitor - Real-time Systems Reporting and Graphing
14)lsof - list open files, network connections and much more
15)ntop web based tool - ntop is the best tool to see network usage in a way similar to what top command does for processes
16)vnstat - vnStat is a console-based network traffic monitor
17)htop - htop is an enhanced version of top
18)mtr - mtr combines the functionality of the traceroute and ping programs in a single network diagnostic tool