Environment Variables - Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual

Use the Log Level menu to set the verbosity of the error messages in the error logs. It can be set
(from least verbose to most verbose) to emerg, alert, crit, error, warn, notice, info or debug. This option
corresponds to the
LogLevel
The value chosen with the Reverse DNS Lookup menu defines the
Choosing No Reverse Lookup sets the value to off. Choosing Reverse Lookup sets the value to on.
Choosing Double Reverse Lookup sets the value to double.
If you choose Reverse Lookup, your server automatically resolves the IP address for each
connection which requests a document from your Web server. Resolving the IP address means
that your server makes one or more connections to the DNS in order to find out the hostname that
corresponds to a particular IP address.
If you choose Double Reverse Lookup, your server performs a double-reverse DNS. In other words,
after a reverse lookup is performed, a forward lookup is performed on the result. At least one of the IP
addresses in the forward lookup must match the address from the first reverse lookup.
Generally, you should leave this option set to No Reverse Lookup, because the DNS requests add a
load to your server and may slow it down. If your server is busy, the effects of trying to perform these
reverse lookups or double reverse lookups may be quite noticeable.
Reverse lookups and double reverse lookups are also an issue for the Internet as a whole. Each
individual connection made to look up each hostname adds up. Therefore, for your own Web server's
benefit, as well as for the Internet's benefit, you should leave this option set to No Reverse Lookup.

22.4.2.4. Environment Variables

Use the Environment tab to configure options for specific variables to set, pass, or unset for CGI
scripts.
Sometimes it is necessary to modify environment variables for CGI scripts or server-side include
(SSI) pages. The Apache HTTP Server can use the mod_env module to configure the environment
variables which are passed to CGI scripts and SSI pages. Use the Environment Variables page to
configure the directives for this module.
Use the Set for CGI Scripts section to set an environment variable that is passed to CGI scripts and
SSI pages. For example, to set the environment variable MAXNUM to 50, click the Add button inside
the Set for CGI Script section, as shown in
the Environment Variable text field and 50 in the Value to set text field. Click OK to add it to the list.
The Set for CGI Scripts section configures the
Use the Pass to CGI Scripts section to pass the value of an environment variable when the server is
first started to CGI scripts. To see this environment variable, type the command env at a shell prompt.
Click the Add button inside the Pass to CGI Scripts section and enter the name of the environment
variable in the resulting dialog box. Click OK to add it to the list. The Pass to CGI Scripts section
configures the
PassEnv
14
http://httpd.apache.org/docs/2.2/mod/core.html#loglevel
15
http://httpd.apache.org/docs/2.2/mod/core.html#hostnamelookups
16
http://httpd.apache.org/docs/2.2/mod/mod_env.html#setenv
17
http://httpd.apache.org/docs/2.2/mod/mod_env.html#passenv
14
directive.
Figure 22.8, "Environment
17
directive.
HostnameLookups
16
directive.
SetEnv
Default Settings
15
directive.
Variables", and type MAXNUM in
327