Red Hat ENTERPRISE LINUX 5 - VIRTUAL SERVER ADMINISTRATION, Руководство по развертыванию

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Default Settings
327
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
14
directive.
The value chosen with the
Reverse DNS Lookup
menu defines the
HostnameLookups
15
directive.
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
Figure 22.8, “Environment Variables”
, and type
MAXNUM
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
SetEnv
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directive.
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
17
directive.
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