Linux Monitoring Tools

Linux has proved itself as the best Operating System worldwide for the server platform. Linux is available in different flavors like Fedora, Ubuntu, CentOS etc. These all distributions of Linux work very well. Most of the times System Administrators and Researchers require to monitor their Linux machines for different purposes like performance monitoring, CPU usage, memory usage, Disk bottlenecks, Network bottlenecks and other serious issue related to System and Network performance. Most of the Linux distributions come equipped with many System and Network monitoring tools which can be run through command line. Some of these tools are given as follows:

The “top” command
The “top” command provides the user with a dynamic real time view of the running system. By default it provides you with the details of running processes that are CPU-intensive. The list of processes with details is updated every 5 seconds in order to keep the user updated with the system status.

There are some hot keys that you can use while the “top” program is running:

• T used to display and hide summary information
• M used to display and hide memory information
• A Sorts the processes with respect to resources usage
• F used for interactive configuration for specific tasks
• O used to customize ordering within the top application
• R used to run the renice command
• K used to kill a process
• Z used for turning on/off color/mono

Vmstat Utility

vmstat utility is used for displaying information regarding the running processes, memory utilization, paging, traps, block IO and the CPU activity. You can use different switches with the vmstat command to view these different pieces of information.
For example, with vmstat 3 you can print the information with 3 seconds interval

There different switches with vmstat command that you can use and display the system information according to your requirements.

The “w” command
The w command shows you the users logged on the server as shown:

The “free” Command
The “free” command displays the total amount of the free and use physical memory and the swap memory on the server as follows:

The “netstat” command
The netstat command displays the information regarding the network connections, network interface statistics, routing tables, multicast memberships and the masquerade connections of the Linux server.

The “iptraf” utility

The “iptraf” utility displays the real time network traffic statistics. It is a colorful interactive utility that generates and displays various types of network statistics like the TCP connections info, ICMP and OSPF information, UDP counts, Ethernet info, node statistics, IP checksum error info and much more.

Nagios – Network and System Monitoring Tool
Nagios is an excellent open source system and network monitoring software application. With Nagios you can easily monitor your network, hosts and the services. This application monitors the network and systems for you and sends alerts when something goes wrong.
With Nagios Software Application you can do the following:

• Monitor you complete network and systems
• Forecast any possible problems that are likely to occur in your IT infrastructure
• Get informed about any mishap that occurs in the network or to a computer
• Perform a security analysis and identify security breaches
• Minimize downtime and financial losses

Some screen shots of Nagios free Edition are given below. A commercial version is also available.

KDE System Guard
KDE System Guard comes with the KDE Desktop. It is a network enable System monitoring tool, that can be run over SSH session. Hence you can monitor the performance of a Linux machine remotely. It is based on a client / server architecture that enables it to monitor local and remote hosts. KDE System guard is not a simple task manager, it is a very powerful tool that can be used to control and monitor a complete server farm of Linux machines. KDE System Guard is shown in the following figure:

Gnome System Monitor
Gnome System monitor is bundled with the Gnome Desktop environment. It is a simple but powerful System monitoring software application that enables you to monitor the System performance, CPU usage, Processes, Memory usage etc on your local Linux system. It is a very useful and informative application for new Linux users and provides information on:

• Basic information about the system software and hardware
• Memory Status
• CPU usage
• Available disk space
• Network Usage
• Running and sleeping processes
• Gnome and Linux Kernel version
• List of all mounted file systems
• Information on installed memory and disk usage

The interface of Gnome system monitor is shown as follows:

The ntop tool
ntop is similar to the top command but it monitors the network usage. With ntop you can monitor the network status, network load, distribution of network with respect to different network protocols like UDP, TCP, HTTP etc.
You can use ntop through command line as well as you can monitor through the web interface at http://localhost:3000/

Cacti (A Web based network monitoring tool)
Cacti is one of the best complete graphical network monitoring tools. Cacti provides advanced user management features. Everything is fixed in a simple easy to use GUI that can be accessed over the web remotely. It is suitable for small LANs to complex large networks. It can provide information regarding network, CPU, memory, Services like Apache, users which are logged in and much more.