Linux Network Administratoramp;#039;s Guide (3rd Edition) [Electronic resources] نسخه متنی

14.3. Configuration File Options

When the Apache software has been
installed in the directory you have selected, you are ready to begin
configuration of the server. Earlier versions of the Apache server
used multiple configuration files. However, now only the
httpd.conf file is required. It is still quite
handy to have multiple configuration files (for example, to make
version upgrades easier). The include option will
allow you to read additional configuration files from the main
httpd.conf file.

Apache comes with a default configuration file that has the most
common options set. If you are in a hurry to have your server
running, this default configuration should cover the requirements to
launch Apache. While functional, this configuration is not acceptable
to many administrators. To begin fine-tuning the configuration, the
first option most administrators choose is selecting the IP address
and port information of the server.

14.3.1. Binding Addresses and Ports

Listen
and BindAddress are the first two options that you
may want to change.

# Listen: Allows you to bind Apache to specific IP addresses and/or
# ports, instead of the default. See also the <VirtualHost>
# directive.
#
#Listen 3000
Listen 172.16.0.4:80

This configuration change enables the Apache server to listen only on
the specified interface and port. You can also use the
BindAddress option to specify the IP address to
which the server will bind. With this option, you are only specifying
the IP address, not the port as above.

# BindAddress: You can support virtual hosts with this option. This directive
# is used to tell the server which IP address to listen to. It can either
# contain "*", an IP address, or a fully qualified Internet domain name.
# See also the <VirtualHost> and Listen directives.
#
BindAddress 172.16.0.4

14.3.2. Logging and Path Configuration Options

When building Apache, you may
have specified the installation directory. If so, the installation
has automatically set the paths for your server root documents and
all of your logfiles. If you need to change this, the following
options will be useful:

ServerRoot

The location of the server's main configuration and
logfiles

DocumentRoot

The location of your HTML documents, or other web content

By default, Apache will log to a path under its main server root
path. If you have a different place on your system where you collect
logs and would like to change the logfile paths, the following
options will require changes:

CustomLog

The location of your access logfile

ErrorLog

The location of your error logfile

There are also some other
useful options that can be set when configuring the logging settings
on Apache:

HostnameLookups

Tells Apache whether it should look up names for logged IP addresses.
It is a good idea to leave this setting turned off, since logging can
be slowed if the server is attempting to resolve all names.

LogLevel

This option tells Apache how much information it should save to the
logfiles. By default it is set at warn, but
possible values are debug,
info, notice,
warn, error,
crit, alert, and
emerg. Each increasing level logs less
information.

LogFormat

With this option, administrators can choose which format the logs are
written in. Items such as date, time, and IP address can be
rearranged to any format desired. The default settings are usually
not changed.

14.3.3. Server Identification Strings

By default, Apache is very friendly
and will provide requesting users with a great deal of information
about itself, including version information, virtual hostname,
administrator name, and so on. Security conscious administrators may
wish to disable this information, as it allows attackers a much
quicker way of enumerating your server. While it is not a foolproof
method of protecting your site, it can slow down would-be attackers
who use automated scanning tools. The following two configuration
options can help you limit the amount of information your server
discloses:

ServerSignature

With this option turned on, the server adds a line to
server-generated pages that includes all of its version information.

ServerTokens

Setting this option to Prod will prevent Apache
from ever disclosing its version number.

14.3.4. Performance Configuration

Sites will always have different
performance requirements. For many sites, the default settings
provided with Apache will deliver all the required performance.
However, busier sites will need to make some changes to the
configuration to increase performance capabilities. The following
options can be used in performance tuning a server. More information
on Apache performance tuning can be found at the Apache Software
Foundation's web site.

Timeout

The number of seconds before Apache will timeout receive and send
requests.

KeepAlive

Enable this option if you want persistent connections enabled. It can
be set to either on or off.

MaxKeepAliveRequests

Set this option to the number of keep-alive requests that you want
the server to allow in persistent connections. Having a higher value
here may increase performance.

KeepAliveTimeout

This is the number of seconds that Apache will wait for a new request
from the current connected session.

Min/MaxSpareServers

These options are used to create a pool of spare servers that Apache
can use when it is busy. Larger sites may wish to increase these
numbers from their defaults. However, for each spare server, more
memory is required on the server.

StartServers

This option tells Apache how many servers to start when first
launched.

MaxClients

This is the option an administrator can use to limit the number of
client sessions to a server. The Apache documentation warns about
setting this option too low because it can adversely affect
availability.

14.3.5. Starting and Stopping Apache with apachectl

If you are
feeling confident that your server is configured, and
you're ready to run it, you will need to use
apachectl, a tool provided with Apache that
allows for the safe startup and shutdown of the server. The available
options of apachectl are as follows:

start

Starts the standard HTTP server

startssl

Starts the SSL servers in addition to the regular server

stop

Shuts down the Apache server

restart

Sends a HUP signal to the running server

fullstatus

Prints out a full status of the web server, but requires
mod_status

status

Displays a shorter version of the above status screen. Requires
mod_status

graceful

Sends a SIGUSR1 to the Apache server

configtest

Inspects the configuration file for errors

While
it's not mandatory to start Apache with
apachectl, it is the recommended and easiest way
to do so. apachectl makes shutting down the
server processes quicker and more efficient, as well.