This glossary defines some of the common terminology related to
Apache in particular, and web serving in general. More information
on each concept is provided in the links.
A perl script that aids in compiling module sources into Dynamic Shared Objects (DSOs) and helps install them in the Apache Web
server. See: Manual Page: apxs
A data record used for authenticating network entities such
as a server or a client. A certificate contains X.509 information pieces
about its owner (called the subject) and the signing Certification Authority (called the
issuer), plus the owner's public key and the
signature made by the CA. Network entities verify these signatures
using CA certificates.
See: SSL/TLS Encryption
A trusted third party whose purpose is to
sign certificates for network entities it has authenticated using
secure means. Other network entities can check the signature to verify
that a CA has authenticated the bearer of a certificate.
See: SSL/TLS Encryption
A standard definition for an interface
between a web server and an external program that allows the external
program to service requests. The interface was originally defined by
NCSA but
there is also an RFC
project.
See: Dynamic Content with CGI
An encrypted text block that validates a certificate or other file. A
Certification Authority creates a
signature by generating a hash of the Public Key embedded in a
Certificate, then encrypting the hash with its own Private
Key. Only the CA's public key can decrypt the signature, verifying
that the CA has authenticated the network entity that owns the
Certificate.
See: SSL/TLS Encryption
Named variables managed by the operating system shell
and used to store information and communicate between programs. Apache also
contains internal variables that are referred to as environment variables,
but are stored in internal Apache structures, rather than in the
shell environment.
See: Environment Variables in Apache
Diminished in cryptographic strength (and security) in order to comply
with the United States' Export Administration Regulations (EAR).
Export-crippled cryptographic software is limited to a small key size,
resulting in Ciphertext which usually can be decrypted by brute
force.
See: SSL/TLS Encryption
A process that is applied to
data that is sent or received by the server. Input filters process
data sent by the client to the server, while output filters process
documents on the server before they are sent to the client. For
example, the INCLUDES output filter processes documents
for Server Side Includes. See: Filters
The unique name of
a network entity, consisting of a hostname and a domain name that can
resolve to an IP address. For example, www is a hostname,
example.com is a domain name, and
www.example.com is a fully-qualified domain name.
An internal Apache
representation of the action to be performed when a file is
called. Generally, files have implicit handlers, based on the file
type. Normally, all files are simply served by the server, but certain
file types are "handled" separately. For example, the
cgi-script handler designates files to be processed as CGIs.
See: Apache's Handler Use
A configuration file that is placed inside
the web tree and applies configuration directives to the directory where it is placed
and all sub-directories. Despite its name, this file can hold almost
any type of directive, not just access-control directives.
See: Configuration Files
The main Apache configuration file.
The default location is /usr/local/apache2/conf/httpd.conf,
but it may be moved using run-time or compile-time configuration.
See: Configuration Files
The standard
transmission protocol used on the World Wide Web. Apache implements
version 1.1 of the protocol, referred to as HTTP/1.1 and defined by RFC 2616.
The HyperText Transport Protocol (Secure), the standard encrypted
communication mechanism on the World Wide Web. This is actually just HTTP
over SSL.
See: SSL/TLS Encryption
In the context of HTTP, an action to perform on a resource, specified
on the request line by the client. Some of the methods available in
HTTP are GET, POST, and PUT.
A way to describe the
kind of document being transmitted. Its name comes from that fact
that its format is borrowed from the Multipurpose Internet Mail
Extensions. It consists of a major type and a minor type, separated
by a slash. Some examples are text/html,
image/gif, and application/octet-stream. In
HTTP, the MIME-type is transmitted in the Content-Typeheader. See: mod_mime
An independent part of a
program. Much of Apache's functionality is contained in modules that
you can choose to include or exclude. Modules that are compiled into
the Apache httpd binary are called static modules, while
modules that are stored separately and can be optionally loaded at
run-time are called dynamic modules or DSOs. Modules that are included by default are called
base modules. Many modules are available for Apache that are
not distributed as part of the Apache HTTP Server tarball. These are referred to as third-party
modules.
See: Module Index
Module Magic Number is a constant defined in the Apache source code
that is associated with binary compatibility of modules. It is changed
when internal Apache structures, function calls and other significant
parts of API change in such a way that binary compatibility cannot be
guaranteed any more. On MMN change, all third party modules have to be
at least recompiled, sometimes even slightly changed in order to work
with the new version of Apache.
The word or phrase
that protects private key files. It prevents unauthorized users from
encrypting them. Usually it's just the secret encryption/decryption
key used for Ciphers. See: SSL/TLS Encryption
An intermediate server that
sits between the client and the origin server. It accepts
requests from clients, transmits those requests on to the origin
server, and then returns the response from the origin server to the
client. If several clients request the same content, the proxy
can deliver that content from its cache, rather than requesting it
from the origin server each time, thereby reducing response time.
See: mod_proxy
The publicly
available key in a Public Key
Cryptography system, used to encrypt messages bound for its owner
and to decrypt signatures made by its owner.
See: SSL/TLS Encryption
The study and application of asymmetric encryption systems, which
use one key for encryption and another for decryption. A corresponding
pair of such keys constitutes a key pair. Also called Asymmetric
Cryptography. See: SSL/TLS Encryption
A way of
describing a pattern in text - for example, "all the words that begin with the
letter A" or "every 10-digit phone number" or even "Every sentence
with two commas in it, and no capital letter Q". Regular expressions
are useful in Apache because they let you apply certain
attributes against collections of files or resources in very flexible
ways - for example, all .gif and .jpg files under any "images"
directory could be written as "/images/.*(jpg|gif)$".
Apache uses Perl Compatible Regular Expressions provided by the
PCRE library.
A proxy server that appears to the client as if it is
an origin server. This is useful to hide the real origin
server from the client for security reasons, or to load balance.
A protocol created by Netscape
Communications Corporation for general communication authentication
and encryption over TCP/IP networks. The most popular usage is
HTTPS, i.e. the HyperText Transfer Protocol (HTTP) over SSL.
See: SSL/TLS Encryption
The successor protocol to SSL, created
by the Internet Engineering Task Force (IETF) for general
communication authentication and encryption over TCP/IP networks. TLS
version 1 and is nearly identical with SSL version 3.
See: SSL/TLS Encryption
The name/address of a resource on the
Internet. This is the common informal term for what is formally
called a Uniform Resource
Identifier. URLs are usually made up of a scheme, like
http or https, a hostname, and a path. A
URL for this page is
http://httpd.apache.org/docs-2.0/glossary.html.
A compact string of characters for
identifying an abstract or physical resource. It is formally defined
by RFC 2396.
URIs used on the world-wide web are commonly referred to
as URLs.
Serving
multiple websites using a single instance of Apache. IP virtual
hosting differentiates between websites based on their IP
address, while name-based virtual hosting uses only the name
of the host and can therefore host many sites on the same IP
address. See: Apache Virtual Host
documentation
An authentication certificate
scheme recommended by the International Telecommunication Union
(ITU-T) which is used for SSL/TLS authentication. See: SSL/TLS Encryption
