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Top Five Open Source Packages for System Administrators
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The cgi.cfg File

The cgi.cfg configuration file has several different functions with the Nagios system. Among the most important is authentication, allowing Nagios and its data to be restricted to appropriate people. Here are some sample directives related to authorization:


The first entry enables the access control mechanism. The next two entries specify users who are allowed to view Nagios configuration information and services status information (respectively). Note that all users also must be authenticated to the Web server using the usual Apache htpasswd mechanism.

This same configuration file is also used to store settings for icon-based status displays, as in these examples:


These entries specify extended attributes for the hosts defined in the entries labeled janine and ishtar. The filenames in this example specify images files for the host in status tables (GIF format--see Figure 3) and in the status map (GD2 format), and the two numeric values specify the device's location--for example, x and y coordinates--within the 2D status map. (Figure 4 provides an example status map display).

The resource.cfg File

The final configuration file we will consider is the resource.cfg file. It is used to define site-specific macros, conventionally named $USER1$ through $USER32$:

# $USER1$ = path to plugins directory

# Store a username and password (hidden)

The first macros defines the path to the Nagios plug-ins directory; this usage is assumed by the supplied sample configuration files.

The other two macros are used in this case to store a username and password. These items can be used in command definitions for added security. The resource.cfg file itself can be protected against all non-root access without compromising the ability of CGI programs to run successfully.

Pre-Checking a Nagios Configuration

Since Nagios configuration is somewhat involved, the package provides a command that can be used to verify it prior to running the program. Here is an example of its use:

# cd /usr/local/nagios/etc
# /usr/local/nagios/bin/nagios -v nagios.cfg

This will check the Nagios configuration, which uses nagios.cfg as its main configuration file.

Essential System Administration Pocket Reference

Related Reading

Essential System Administration Pocket Reference
Commands and File Formats
By Æleen Frisch


For more information about Nagios, including installation instructions, and how to initiate and manage monitoring, consult the following sources:

If you liked this article and would like to receive the free ESA3 newsletter, you can sign up here.

You may also like AEleen's latest book, the just-released System Administration Pocket Reference.

Æleen Frisch has been a system administrator for over 20 years, tending a plethora of VMS, Unix, Macintosh, and Windows systems. If you liked this article and would like to receive the free ESA3 newsletter, you can sign up at

O'Reilly & Associates recently released (August 2002) Essential System Administration, 3rd Edition.

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