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Introduction to Linux - A Hands on Guide
This guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started guide, with exercises at the end of each chapter.
For more advanced trainees it can be a desktop reference, and a collection of the base knowledge needed to proceed with system and network administration. This book contains many real life examples derived from the author's experience as a Linux system and network administrator, trainer and consultant. They hope these examples will help you to get a better understanding of the Linux system and that you feel encouraged to try out things on your own.
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When using Linux in a business environment, it's important to monitor resource utilization. System monitoring helps with capacity planning, alerts you to performance problems, and generally makes managers happy.
So, in this month's "Tech Support," let's install Cacti, a resource monitoring application that utilizes RRDtool as a back-end. RRDTool stores and displays time-series data, such as network bandwidth, machine-room temperature, and server load average. With Cacti and RRDtool, you can graph system performance in a way that will not only make it more useful, it'll also impress your pointy-haired boss.
$ ./configure; make
# make install; make site-perl-install
To ease upgrades, you should also link /usr/local/rrdtool to the /usr/local/rrdtool-version directory created by make install.
Now that you have RRDtool installed, you're ready to install Cacti. Cacti is a complete front-end to RRDtool (based on PHP and MySQL) that stores all of the information necessary to create and populate performance graphs. Cacti utilizes templates, supports multiple graphing hierarchies, and has its own user-based authentication system, which allows administrators to create users and assign them different permissions to the Cacti interface. Also licensed under the GPL, Cacti can be downloaded from http://www.raxnet.net/products/cacti.
The first step to install Cacti is to unpack its tarball into a directory accessible via your web server. Next, create a MySQL database and user for Cacti (this article uses cacti as the database name). Optionally, you can also create a system account to run Cacti's cron jobs.
Once the Cacti database is created, import its contents by running mysql cacti < cacti.sql. Depending on your MySQL setup, you may need to supply a username and password for this step.
After you've imported the database, edit include/config.php and specify your Cacti MySQL database information. Also, if you plan to run Cacti as a user other than the one you're installing it as, set the appropriate permissions on Cacti's directories for graph/log generation. To do this, type chown cactiuser rra/ log/ in the Cacti directory.
... replacing /path/to/php with the full pathname to your command-line PHP binary and /path/to/www/cacti with the web accessible directory you unpacked the Cacti tarball into.
Now, point your web browser to http://your-server/cacti/ and login with the default username and password of admin and admin. You must change the administrator password immediately. Then, make sure you carefully fill in all of the path variables on the next screen.
By default, Cacti only monitors a few items, such as load average, memory usage, and number of processes. While Cacti comes pre-configured with some additional data input methods and understands SNMP if you have it installed, its power lies in the fact that you can graph data created by an arbitrary script. You can find a list of contributed scripts at http://www.raxnet.net/products/cacti/additional_scripts.php, but you can easily write a script for almost anything.
To create a new graph, click on the "Console" tab and create a data input method to tell Cacti how to call the script and what to expect from it. Next, create a data source to tell Cacti how and where the data is stored, and create a graph to tell Cacti how to display the data. Finally, add the new graph to the "Graph View" to see the results.
While Cacti is a very powerful program, many other applications also utilize the power of RRDtool, including Cricket, FlowScan, OpenNMS, and SmokePing. Cricket is a high performance, extremely flexible system for monitoring trends in time-series data. FlowScan analyzes and reports on Internet Protocol (IP) flow data exported by routers and produces graph images that provide a continuous, near real-time view of network border traffic. OpenNMS is an open source project dedicated to the creation of an enterprise grade network management platform. And SmokePing measures latency, latency distribution, and packet loss in your network.