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| <manualpage metafile="glossary.xml.meta"> |
| |
| <title>Glossary</title> |
| |
| <summary> |
| <p>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.</p> |
| </summary> |
| |
| <section id="definitions"><title>Definitions</title> |
| |
| <dl> |
| <dt><a name="accesscontrol" id="accesscontrol">Access Control</a></dt> |
| <dd>The restriction of access to network realms. In an Apache context |
| usually the restriction of access to certain <em>URLs</em>.<br /> See: <a |
| href="howto/auth.html">Authentication, Authorization, and Access |
| Control</a> |
| </dd> |
| |
| <dt><a name="algorithm" id="algorithm">Algorithm</a></dt> |
| <dd>An unambiguous formula or set of rules for solving a problem in a finite |
| number of steps. Algorithms for encryption are usually called |
| <dfn>Ciphers</dfn>. |
| </dd> |
| |
| <dt><a name="apacheextensiontool" id="apacheextensiontool">APache |
| eXtension Tool</a> <a name="apxs" id="apxs">(apxs)</a></dt> |
| <dd>A perl script that aids in compiling <glossary |
| ref="module">module</glossary> sources into Dynamic Shared Objects |
| (<glossary ref="dso">DSO</glossary>s) and helps install them in the |
| Apache Web server.<br /> |
| See: Manual Page: <program>apxs</program> |
| </dd> |
| |
| <dt><a name="apacheportableruntime" |
| id="apacheportableruntime">Apache Portable Runtime</a> <a |
| name="apr" id="apr">(APR)</a></dt> |
| <dd>A set of libraries providing many of the basic interfaces |
| between the server and the operating system. APR is developed |
| parallel to the Apache HTTP Server as an independent project.<br /> |
| See: <a href="http://apr.apache.org/">Apache Portable Runtime |
| Project</a> |
| </dd> |
| |
| <dt><a name="authentication" id="authentication">Authentication</a></dt> |
| <dd>The positive identification of a network entity such as a server, a |
| client, or a user.<br /> |
| See: <a href="howto/auth.html">Authentication, Authorization, and Access |
| Control</a> |
| </dd> |
| |
| <dt><a name="certificate" id="certificate">Certificate</a></dt> |
| <dd>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 <glossary |
| ref="certificationauthority">Certification Authority</glossary> (called |
| the issuer), plus the owner's <glossary ref="publickey">public |
| key</glossary> and the |
| signature made by the CA. Network entities verify these signatures |
| using CA certificates.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="certificatsigningrequest" |
| id="certificatsigningrequest">Certificate Signing Request</a> |
| <a name="csr" id="csr">(CSR)</a></dt> |
| <dd>An unsigned <glossary ref="certificate">certificate</glossary> for |
| submission to a <glossary ref="certificationauthority">Certification |
| Authority</glossary>, which signs it with the <glossary |
| ref="privatekey">Private Key</glossary> of their CA |
| <em>Certificate</em>. Once the CSR is signed, it becomes a real |
| certificate.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="certificationauthority" |
| id="certificationauthority">Certification Authority</a> |
| <a name="ca" id="ca">(CA)</a></dt> |
| <dd>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.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="cipher" id="cipher">Cipher</a></dt> |
| <dd>An algorithm or system for data encryption. Examples are DES, IDEA, RC4, |
| etc.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="ciphertext" id="ciphertext">Ciphertext</a></dt> |
| <dd>The result after <glossary ref="plaintext">Plaintext</glossary> is |
| passed through a <glossary ref="cipher">Cipher</glossary>.<br /> See: <a |
| href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="commongatewayinterface" id="commongatewayinterface">Common |
| Gateway Interface</a> <a name="cgi" id="cgi">(CGI)</a></dt> |
| <dd>A standard definition for an interface between a web server and an |
| external program that allows the external program to service requests. |
| There is an <a href="http://www.ietf.org/rfc/rfc3875">Informational |
| RFC</a> which covers the specifics.<br /> |
| See: <a href="howto/cgi.html">Dynamic Content with CGI</a> |
| </dd> |
| |
| <dt><a name="configurationdirective" |
| id="configurationdirective">Configuration Directive</a></dt> |
| <dd>See: <glossary ref="directive">Directive</glossary></dd> |
| |
| <dt><a name="configurationfile" id="configurationfile">Configuration |
| File</a></dt> |
| <dd>A text file containing <glossary ref="directive">Directives</glossary> |
| that control the configuration of Apache.<br /> |
| See: <a href="configuring.html">Configuration Files</a> |
| </dd> |
| |
| <dt><a name="connect" id="connect">CONNECT</a></dt> |
| <dd>An HTTP <glossary ref="method">method</glossary> for proxying raw data |
| channels over HTTP. It can be used to encapsulate other protocols, such as |
| the SSL protocol. |
| </dd> |
| |
| <dt><a name="context" id="context">Context</a></dt> |
| <dd>An area in the <glossary ref="configurationfile">configuration |
| files</glossary> where certain types of <glossary |
| ref="directive">directives</glossary> are allowed.<br /> |
| See: <a href="mod/directive-dict.html#Context">Terms Used to Describe |
| Apache Directives</a> |
| </dd> |
| |
| <dt><a name="digitalsignature" id="digitalsignature">Digital |
| Signature</a></dt> |
| <dd>An encrypted text block that validates a certificate or other file. A |
| <glossary ref="certificationauthority">Certification Authority</glossary> |
| creates a signature by generating a hash of the <em>Public Key</em> |
| embedded in a <em>Certificate</em>, then encrypting the hash with its own |
| <em>Private Key</em>. Only the CA's public key can decrypt the signature, |
| verifying that the CA has authenticated the network entity that owns the |
| <em>Certificate</em>.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="directive" id="directive">Directive</a></dt> |
| <dd>A configuration command that controls one or more aspects of Apache's |
| behavior. Directives are placed in the <glossary |
| ref="configurationfile">Configuration File</glossary><br /> |
| See: <a href="mod/directives.html">Directive Index</a> |
| </dd> |
| |
| <dt><a name="dynamicsharedobject" id="dynamicsharedobject">Dynamic |
| Shared Object</a> <a name="dso" id="dso">(DSO)</a></dt> |
| <dd><glossary ref="module">Modules</glossary> compiled separately from the |
| Apache <program>httpd</program> binary that can be loaded on-demand.<br /> |
| See: <a href="dso.html">Dynamic Shared Object Support</a> |
| </dd> |
| |
| <dt><a name="environmentvariable" id="environmentvariable">Environment |
| Variable</a> <a name="env-variable" |
| id="env-variable">(env-variable)</a></dt> |
| <dd>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.<br /> |
| See: <a href="env.html">Environment Variables in Apache</a> |
| </dd> |
| |
| <dt><a name="export-crippled" id="export-crippled">Export-Crippled</a></dt> |
| <dd>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 <em>Ciphertext</em> which usually can be decrypted by brute |
| force.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="filter" id="filter">Filter</a></dt> |
| <dd>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 <code>INCLUDES</code> output filter |
| processes documents for <glossary ref="ssi">Server Side |
| Includes</glossary>.<br /> |
| See: <a href="filter.html">Filters</a> |
| </dd> |
| |
| <dt><a name="fully-qualifieddomain-name" |
| id="fully-qualifieddomain-name">Fully-Qualified Domain-Name</a> |
| <a name="fqdn" id="fqdn">(FQDN)</a></dt> |
| <dd>The unique name of a network entity, consisting of a hostname and a |
| domain name that can resolve to an IP address. For example, |
| <code>www</code> is a hostname, <code>example.com</code> is a domain name, |
| and <code>www.example.com</code> is a fully-qualified domain name. |
| </dd> |
| |
| <dt><a name="handler" id="handler">Handler</a></dt> |
| <dd>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 |
| <code>cgi-script</code> handler designates files to be processed as |
| <glossary ref="cgi">CGIs</glossary>.<br /> |
| See: <a href="handler.html">Apache's Handler Use</a> |
| </dd> |
| |
| <dt><a name="hash" id="hash">Hash</a></dt> |
| <dd>A mathematical one-way, irreversible algorithm generating a string with |
| fixed-length from another string of any length. Different input strings |
| will usually produce different hashes (depending on the hash function). |
| </dd> |
| |
| <dt><a name="header" id="header">Header</a></dt> |
| <dd>The part of the <glossary ref="http">HTTP</glossary> request and |
| response that is sent before the actual content, and that contains |
| meta-information describing the content. |
| </dd> |
| |
| <dt><a name="htaccess" id="htaccess">.htaccess</a></dt> |
| <dd>A <glossary ref="configurationfile">configuration file</glossary> that |
| is placed inside the web tree and applies configuration <glossary |
| ref="directive">directives</glossary> 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.<br /> |
| See: <a href="configuring.html">Configuration Files</a> |
| </dd> |
| |
| <dt><a name="httpd.conf" id="httpd.conf">httpd.conf</a></dt> |
| <dd>The main Apache <glossary ref="configurationfile">configuration |
| file</glossary>. The default location is |
| <code>/usr/local/apache2/conf/httpd.conf</code>, but it may be moved using |
| run-time or compile-time configuration.<br /> |
| See: <a href="configuring.html">Configuration Files</a> |
| </dd> |
| |
| <dt><a name="hypertexttransferprotocol" |
| id="hypertexttransferprotocol">HyperText Transfer Protocol</a> |
| <a name="http" id="hhtp">(HTTP)</a></dt> |
| <dd>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 <a href="http://ietf.org/rfc/rfc2616.txt">RFC 2616</a>. |
| </dd> |
| |
| <dt><a name="https" id="https">HTTPS</a></dt> |
| <dd>The HyperText Transfer Protocol (Secure), the standard encrypted |
| communication mechanism on the World Wide Web. This is actually just HTTP |
| over <glossary ref="ssl">SSL</glossary>.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="method" id="method">Method</a></dt> |
| <dd>In the context of <glossary ref="http">HTTP</glossary>, an action to |
| perform on a resource, specified on the request line by the client. Some |
| of the methods available in HTTP are <code>GET</code>, <code>POST</code>, |
| and <code>PUT</code>. |
| </dd> |
| |
| <dt><a name="messagedigest" id="messagedigest">Message Digest</a></dt> |
| <dd>A hash of a message, which can be used to verify that the contents of |
| the message have not been altered in transit.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="mime-type" id="mime-type">MIME-type</a></dt> |
| <dd>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 <code>text/html</code>, |
| <code>image/gif</code>, and <code>application/octet-stream</code>. In |
| HTTP, the MIME-type is transmitted in the <code>Content-Type</code> |
| <glossary ref="header">header</glossary>.<br /> |
| See: <a href="mod/mod_mime.html">mod_mime</a> |
| </dd> |
| |
| <dt><a name="module" id="module">Module</a></dt> |
| <dd>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 <program>httpd</program> binary are |
| called <dfn>static modules</dfn>, while modules that are stored |
| separately and can be optionally loaded at run-time are called |
| <dfn>dynamic modules</dfn> or <glossary ref="dso">DSOs</glossary>. |
| Modules that are included by default |
| are called <dfn>base modules</dfn>. Many modules are available for Apache |
| that are not distributed as part of the Apache HTTP Server <glossary |
| ref="tarball">tarball</glossary>. These are referred to as |
| <dfn>third-party modules</dfn>.<br /> |
| See: <a href="mod/">Module Index</a> |
| </dd> |
| |
| <dt><a name="modulemagicnumber" id="modulemagicnumber">Module Magic |
| Number</a> (<a name="mmn" id="mmn">MMN</a>)</dt> |
| <dd>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. |
| </dd> |
| |
| <dt><a name="openssl" id="openssl">OpenSSL</a></dt> |
| <dd>The Open Source toolkit for SSL/TLS<br /> |
| See <a href="http://www.openssl.org/">http://www.openssl.org/</a># |
| </dd> |
| |
| <dt><a name="passphrase" id="passphrase">Pass Phrase</a></dt> |
| <dd>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 <glossary |
| ref="cipher">Ciphers</glossary>.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="plaintext" id="plaintext">Plaintext</a></dt> |
| <dd>The unencrypted text.</dd> |
| |
| <dt><a name="privatekey" id="privatekey">Private Key</a></dt> |
| <dd>The secret key in a <glossary ref="publickeycryptography">Public Key |
| Cryptography</glossary> system, used to decrypt incoming messages and |
| sign outgoing ones.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="proxy" id="proxy">Proxy</a></dt> |
| <dd>An intermediate server that sits between the client and the <em>origin |
| server</em>. 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.<br /> |
| See: <a href="mod/mod_proxy.html">mod_proxy</a> |
| </dd> |
| |
| <dt><a name="publickey" id="publickey">Public Key</a></dt> |
| <dd>The publicly available key in a <glossary |
| ref="publickeycryptography">Public Key Cryptography</glossary> system, |
| used to encrypt messages bound for its owner and to decrypt signatures |
| made by its owner.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="publickeycryptography" |
| id="publickeycryptography">Public Key Cryptography</a></dt> |
| <dd>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. |
| <br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="regularexpresion" id="regularexpresion">Regular Expression</a> |
| <a name="regex" id="regex">(Regex)</a></dt> |
| <dd>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 "<code>/images/.*(jpg|gif)$</code>". In places where |
| regular expressions are used to replace strings, the special variables |
| $1 ... $9 contain backreferences to the grouped parts (in parentheses) of |
| the matched expression. The special variable $0 contains a backreference |
| to the whole matched expression. To write a literal dollar sign in a |
| replacement string, it can be escaped with a backslash. Historically, the |
| variable & could be used as alias for $0 in some places. This is no |
| longer possible since version 2.3.6. Apache uses Perl Compatible Regular |
| Expressions provided by the <a href="http://www.pcre.org/">PCRE</a> |
| library. You can find more documentation about PCRE's regular expression |
| syntax at that site, or at |
| <a href="http://en.wikipedia.org/wiki/PCRE">Wikipedia</a>. |
| </dd> |
| |
| <dt><a name="reverseproxy" id="reverseproxy">Reverse Proxy</a></dt> |
| <dd>A <glossary ref="proxy">proxy</glossary> server that appears to the client |
| as if it is an <em>origin server</em>. This is useful to hide the real |
| origin server from the client for security reasons, or to load balance. |
| </dd> |
| |
| <dt><a name="securesocketslayer" id="securesocketslayer">Secure Sockets |
| Layer</a> <a name="ssl" id="ssl">(SSL)</a></dt> |
| <dd>A protocol created by Netscape Communications Corporation for general |
| communication authentication and encryption over TCP/IP networks. The most |
| popular usage is <em>HTTPS</em>, i.e. the HyperText Transfer Protocol (HTTP) |
| over SSL.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="servernameindication" id="servernameindication">Server Name |
| Indication</a> <a name="sni" id="sni">(SNI)</a></dt> |
| <dd>An SSL function that allows passing the desired server |
| hostname in the initial SSL handshake message, so that the web |
| server can select the correct virtual host configuration to use |
| in processing the SSL handshake. It was added to SSL starting |
| with the TLS extensions, RFC 3546. <br /> |
| See: <a href="ssl/ssl_faq.html">the SSL FAQ</a> |
| and <a href="http://www.ietf.org/rfc/rfc3546.txt">RFC 3546</a> |
| </dd> |
| |
| <dt><a name="serversideincludes" id="serversideincludes">Server Side |
| Includes</a> <a name="ssi" id="ssi">(SSI)</a></dt> |
| <dd>A technique for embedding processing directives inside HTML files.<br /> |
| See: <a href="howto/ssi.html">Introduction to Server Side Includes</a> |
| </dd> |
| |
| <dt><a name="session" id="session">Session</a></dt> |
| <dd>The context information of a communication in general.</dd> |
| |
| <dt><a name="ssleay" id="ssleay">SSLeay</a></dt> |
| <dd>The original SSL/TLS implementation library developed by Eric A. |
| Young |
| </dd> |
| |
| <dt><a name="subrequest" id="subrequest">Subrequest</a></dt> |
| <dd>Apache provides a subrequest API to modules that allows other |
| filesystem or URL paths to be partially or fully evaluated by |
| the server. Example consumers of this API are |
| <directive module="mod_dir">DirectoryIndex</directive>, |
| <module>mod_autoindex</module>, and <module>mod_include</module>. |
| </dd> |
| |
| <dt><a name="symmetriccryptophraphy" id="symmetriccryptophraphy">Symmetric |
| Cryptography</a></dt> |
| <dd>The study and application of <em>Ciphers</em> that use a single secret key |
| for both encryption and decryption operations.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="tarball" id="tarball">Tarball</a></dt> |
| <dd>A package of files gathered together using the <code>tar</code> utility. |
| Apache distributions are stored in compressed tar archives or using |
| pkzip. |
| </dd> |
| |
| <dt><a name="transportlayersecurity" id="transportlayersecurity">Transport |
| Layer Security</a> <a name="tls" id="tls">(TLS)</a></dt> |
| <dd>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 is nearly identical with SSL version 3.<br /> |
| See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| |
| <dt><a name="uniformresourcelocator" id="uniformresourcelocator">Uniform |
| Resource Locator</a> <a name="url" id="url">(URL)</a></dt> |
| <dd>The name/address of a resource on the Internet. This is the common |
| informal term for what is formally called a <glossary |
| ref="uniformresourceidentifier">Uniform Resource Identifier</glossary>. |
| URLs are usually made up of a scheme, like <code>http</code> or |
| <code>https</code>, a hostname, and a path. A URL for this page might |
| be <code>http://httpd.apache.org/docs/&httpd.docs;/glossary.html</code>. |
| </dd> |
| |
| <dt><a name="uniformresourceidentifier" |
| id="uniformresourceidentifier">Uniform Resource Identifier</a> |
| <a name="URI" id="URI">(URI)</a></dt> |
| <dd>A compact string of characters for identifying an abstract or physical |
| resource. It is formally defined by <a |
| href="http://www.ietf.org/rfc/rfc2396.txt">RFC 2396</a>. URIs used on the |
| world-wide web are commonly referred to as <glossary |
| ref="url">URLs</glossary>. |
| </dd> |
| |
| <dt><a name="virtualhosting" id="virtualhosting">Virtual Hosting</a></dt> |
| <dd>Serving multiple websites using a single instance of Apache. <em>IP |
| virtual hosting</em> differentiates between websites based on their IP |
| address, while <em>name-based virtual hosting</em> uses only the name of the |
| host and can therefore host many sites on the same IP address.<br /> |
| See: <a href="vhosts/">Apache Virtual Host documentation</a> |
| </dd> |
| |
| <dt><a name="x.509" id="x.509">X.509</a></dt> |
| <dd>An authentication certificate scheme recommended by the International |
| Telecommunication Union (ITU-T) which is used for SSL/TLS authentication.<br |
| /> See: <a href="ssl/">SSL/TLS Encryption</a> |
| </dd> |
| </dl> |
| </section> |
| </manualpage> |
