Free system monitoring tools software for linux

ROX System Monitor displays a large window containing two bar charts. One shows the Free/Used space on each mounted filesystem, and the other shows a list of processes with Shared/Unshared/Paged-out memory.
A popup menu allows processes to be paused, resumed, or killed. The aim is to show the information you normally want from a system viewer without the clutter.
Main features:
- Displays Shared/Unshared/Swapped memory for each process.
- State indicator beside each process shows current state (running, sleeping, etc).
- Popup menu allows processes to be paused, resumed and killed.
- Displays Reserved/Used/Free space for each filesystem.

System Health Monitor for Linux is a handy python program that will setup your system to generate RRD Graphs of network interface traffic, system load, memory usage, disk space and inode usage and graphs of the number of running processes.

System Health Monitor features a user-friendly interactive configuration mode and auto-generated html pages. Just point your web server to the health_html directory to get an overview of the status of your machine. You can see examples of it in operation here on my machine and on KPLUG.org

Shell SYStem Monitor a basic console ncurses application for system monitoring.
Shell SYStem Monitor will show things like CPU load, memory load, uptime, Ethernet load (bandwidth usage in KB/s), server time, and more.
Install code:
# cd ssysm
# make
(as root)
# make install
Uninstall code:
(as root)
# make uninstall
Enhancements:
- There was a bug which occurred when outgoing bandwidth exceeds 2GiB, in which the TX bandwidth stays at 0 and TX byte counter sticks to 2GiB.
- This has finally been fixed. However, the byte count still resets to 0 when the interface exceeds 4GiB.

Metalklesk System Monitor Crystal is a SuperKaramba theme modified from the System Monitor Crystal Clear theme and nvidiaGPUsensorsV0.3 theme, in fact is a fusion but with some changes (it doesnt need nvclock for Nvidia cards to take the data).

You can adjust it just editing .theme file with your favorite text editor (e.g. Kate).

This version is in Spanish only, but its very easy to change to your language.

TyopoytaORvelo System MOnitor is a system monitor for Linux that sits in the corner of your desktop. TyopoytaORvelo System MOnitor renders itself on the root window (on the desktop) or to its own transparent window any special eyecandy.
TyopoytaORvelo System MOnitor can show lots of info about your system, including:
- kernel version
- uptime
- network interface information
- memory and swap usage
- hostname
- machine, i686 for example
- system name, Linux for example
- temperatures from i2c-sensors
Installation:
The `configure shell script attempts to guess correct values for various system-dependent variables used during compilation.
It uses those values to create a `Makefile in each directory of the package. It may also create one or more `.h files containing system-dependent definitions.
Finally, it creates a shell script `config.status that you can run in the future to recreate the current configuration, a file `config.cache that saves the results of its tests to speed up reconfiguring, and a file `config.log containing compiler output (useful mainly for debugging `configure).
If you need to do unusual things to compile the package, please try to figure out how `configure could check whether to do them, and mail diffs or instructions to the address given in the `README so they can be considered for the next release.
If at some point `config.cache contains results you dont want to keep, you may remove or edit it.
The file `configure.in is used to create `configure by a program called `autoconf. You only need `configure.in if you want to change it or regenerate `configure using a newer version of `autoconf.
The simplest way to compile this package is:
1. `cd to the directory containing the packages source code and type `./configure to configure the package for your system. If youre using `csh on an old version of System V, you might need to type `sh ./configure instead to prevent `csh from trying to execute
`configure itself.
Running `configure takes awhile. While running, it prints some messages telling which features it is checking for.
2. Type `make to compile the package.
3. Optionally, type `make check to run any self-tests that come with the package.
4. Type `make install to install the programs and any data files and documentation.
5. You can remove the program binaries and object files from the source code directory by typing `make clean. To also remove the files that `configure created (so you can compile the package for a different kind of computer), type `make distclean.
There is also a `make maintainer-clean target, but that is intended mainly for the packages developers. If you use it, you may have to get all sorts of other programs in order to regenerate files that came with the distribution.

Monitoring API project is a multi-user programming interface designed to simplify the development of network monitoring software and allows users to express their monitoring needs in a device-independent way.
The main abstraction provided by MAPI is the network flow. Although flows have been used before in network monitoring systems, MAPI gives flows a first-class status. Applications that uses MAPI can specify what flows or flow statistics they are interested in by applying functions to flows.
A MAPI function can be a BPF filter, string search, packet counter or more advanced like a NetFlow generator. These function will automatically run in hardware if there is support for it on the hardware being used.
MAPI currently supports the following hardware:
- Normal NICs through libpcap
- DAG cards without co-processor
- SCAMPI adapter
Enhancements:
- This release includes support for distributed monitoring, several new MAPI functions, demo applications, and a lot of bugfixes.