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System administrators need to keep an eye on their servers to make sure things are running smoothly. If they find a problem, they need to see when it started, so investigations can focus on what happened at that time. That means logging information at regular intervals and having a quick way to analyse this data. Here's a look at several tools that let you monitor one or more servers from a Web interface.
While collectd emphasizes data collection, Cacti is oriented toward providing a nice Web front end to your system information. Whereas collectd runs as a daemon and collects its information every 10 seconds without spawning processes, Cacti runs a PHP script every five minutes to collect information. (These time intervals for the two projects are the defaults and are both user configurable.) The difference in default values gives an indication of how frequently each project thinks system information should be gathered.
Cacti is packaged for Etch, Fedora 9, and openSUSE 11. I used the Fedora packages on a 64-bit Fedora 9 machine.
Once you have installed Cacti, you might get the following error when you try to visit http://localhost/cacti if your packages have not set up a database for you. The Cacti Web site has detailed instructions to help you set up your MySQL database and configure Cacti to connect.
FATAL: Cannot connect to MySQL server on 'localhost'. Please make sure you have specified a valid MySQL database name in 'include/config.php'
When you first connect to your Cacti installation in a Web browser you are presented with a wizard to complete the configuration. Cacti presents you with the paths to various tools, SNMP settings, and the PHP binary, and asks which version of rrdtool you have. Although Cacti found my rrdtool, I still had to tell it explicitly the version of rrdtool I had. While this information was easy to supply, a button on the wizard offering to execute rrdtool and figure it out from the
--version string would have been a plus.
After the paths and versions are collected Cacti will ask you to log in using the default username and password. When you log in you immediately have to change the admin user's password.
The first screen you are taken to is the console tab. In the main section of the window you are offered three options: create devices, create graphs, and view your graphs. This might lead you to believe that there are no graphs already created. Clicking on the graphs tab you should see that you already have a small collection of graphs: Memory Usage, Load Average, Logged in Users, and Processes. The graphs view is shown in the screenshot below.
Additional information-gathering scripts available for Cacti let you expand what information Cacti can monitor. For example, they let you collect the load and input and output voltage of UPS devices.
Most of these projects' Web interfaces allow you to view your statistics using predefined time intervals such as hour, day, and week. Cacti goes a big step further and allows you to specify the exact interval that you are interested in through the Web interface.
Cacti offers the most functional and polished Web interface among these projects. It lets you select the time interval displayed on your graphs from more predefined settings, and it also lets you explicitly nominate the start and end time you are interested in. Cacti is the only one of the tools that lets you nominate a custom time range for your graph.