Page tree
Skip to end of metadata
Go to start of metadata



“A” (Address) Entry

A record that resides on your server and that contains your server’s hostname and IP address. The “A” entry is essential because it tells DNS servers the identity of your server, which allows visitors to find your server on the Internet.


A record that allows you to access privatized information. For example, your cPanel account allows you to manage your website. In cPanel, other instances of the term “account” occur in email and FTP.

Account-Level Filter

A rule that determines where you wish to deliver email that was delivered to a domain's main email account and that meets certain criteria. 

ACLs (Access Control Lists)

Permissions that a server's owner grants to a reseller. You can define ACLs in the Edit Privileges section of WHM's Reseller Center interface. (Do not confuse Access Control Lists with Account Creation Limits.)

Addon Domain

An additional domain name that is associated with a cPanel account. Each addon domain is stored in its own directory, which can be configured by website owners. This allows website owners to manage multiple domains from a single cPanel account. Addon domains must be registered with a domain name registrar in order to properly function.

Addons (cPAddons)

Additional services, which are usually provided by cPanel, for your users. (For example, blogs, message boards, and shopping carts.)

AIM (AOL Instant Messenger)

A widely used instant messaging program. WHM can notify you by AIM if there is a problem with your server. For more information, visit the AIM website.


A program that provides information about the visitors to a website in both graphical and statistical views. For more information, visit the Analog website.

Anonymous FTP

A process through which visitors who do not have FTP accounts may upload and download files to and from a website. Although it poses security risks, anonymous FTP is convenient if the site owner wishes to make files publicly available to download. When you set up anonymous FTP, it is important to change file permissions and directory access permissions in order to protect any sensitive information.


Web server software, a program that receives requests from web browsers and "serves" web pages to the browsers. 

Apache Handler

A means by which you can determine how the Apache software processes a specific type of file. By default, Apache only handles certain file types. You can configure Apache handlers for other file types with cPanel. For more information, see Apache's handler documentation.

ASCII (American Standard Code for Information Interchange)

A common character set that is based on the English alphabet.


A daemon for the at command in Linux operating systems, which performs scheduled tasks. WHM's Quick Security Scan feature disables this daemon.


A process that allows you to confirm the identity of someone with whom the server will share sensitive information. On the web, authentication usually involves either a username and password set or a public and private key pair.

Auto Responder

Auto responders allow you to automate replies to incoming email. In cPanel, this feature can be useful to confirm the receipt of mail, or to inform correspondents that the recipient is unavailable (for example, while on vacation).


A process that sets up users' Outlook® or Outlook Express accounts to receive their cPanel email. You can enable or disable this feature in WHM's Enable/Disable Outlook® Autoconfig feature. This feature was not available in cPanel & WHM version 11.34.

AWStats (Advanced Web Statistics)

A program that provides information about the visitors to a website. AWStats presents information in both graphical and statistical views. For more information, visit the AWStats website.




Backscatter is the term for bounced email messages (or failed Delivery Status Notifications) that were erroneously sent to a domain when the domain's name was forged as the sender of spam. Use SPF on your mail server to reduce backscatter.


A copy of your website’s files, directories, databases, and email configurations. We recommend that you keep a backup copy of your website on your personal computer.


Bandmin is a set of Perl scripts that monitor and log bandwidth usage by IP address. You can access Bandmin at, where is your domain name.


The amount of data that is transferred to and from a server. Every time a visitor views a file, whether it’s a web page, image, video, or audio file, that file is transferred to the visitor’s computer. Bandwidth is the total size of all of the files that are transferred to visitors’ computers. Hosting providers often limit a site owner's bandwidth, because it can affect the performance of the server.

Bandwidth Limit

A limit that is imposed on the amount of data (bandwidth) that an account is allowed to transfer per month.


Images that appear on a website, often as advertisements at the top or bottom of a page. Many banners alternate with each successive visit to the page.

Bayes Testing (aka Bayesian Spam Filtering)

Bayesian spam filtering is a method by which you can filter spam based on statistics. This method uses tokens (generally words) that are found in emails to determine whether an incoming message is spam. This technique relies on Bayesian statistics. Bayesian classifiers correlate the use of tokens with spam and non spam emails to calculate a probability that an email is or is not spam.

BIND (Berkeley Internet Name Domain)

The most prominently used DNS server software, it is also referred to as named. For more information, visit the BIND website.


One of the options for how to handle mail that is received by the default or catch-all email addresses of cPanel users. The “blackhole” option discards mail after it is accepted. For this reason, it may result in additional spam that is sent to your users, and it places a larger load on your server than the “fail” option.


A blocker is a check that is performed before a version change takes place. This check reviews your system for possible compatibility issues with a desired upgrade. This concept was introduced in cPanel & WHM version 11.30.

Bounce Message

An email reply that informs a sender that there was a problem with email delivery.


An application that is included with cPanel and that requires would-be senders to reply to a verification email in order to filter spam (also known as challenge-response verification). The original email will only be accepted after the sender replies to the verification message.

BoxTrapper Blacklist

A list of email addresses from which incoming mail will be automatically blocked by the BoxTrapper application. cPanel automatically sends a configurable warning message on receipt of mail from a blacklisted address.

BoxTrapper Ignore List

A list of email addresses from which incoming mail will be blocked. cPanel does not send a warning message on receipt of mail from an address that is ignored by the BoxTrapper application.

BoxTrapper Whitelist

A list of email addresses from which incoming mail will automatically be accepted by the BoxTrapper application.

Brute Force (Attack)

A type of attack wherein the attacker enters a large number of combinations of characters, in an attempt to decrypt a key. WHM includes cPHulk, a protection system that allows you to lock out brute force attackers after a specified number of failed attempts.


A copy of cPanel & WHM software that has a specific version number. All cPanel & WHM builds are released in different stages through Release Tiers.


A unit of measure for digital memory storage. One byte represents a group of eight bits (binary digits).



CA (Certificate Authority) Bundle

A file on your server that verifies that your public and private keys were issued by a trusted entity. If your Certificate Authority sent you a CA bundle file, you can install it to your server with WHM’s Install a SSL Certificate and Setup the Domain feature, or the Manage Service SSL Certificates feature.


Stored information that the server accesses, in place of the information source, to save bandwidth and time. In WHM, you can configure DNS record caches in the Edit DNS Zone feature. You can configure disk usage cache data in WHM's Tweak Settings interface.

Catch-All Address

The email address to which cPanel & WHM software routes any email message that is sent to email accounts that do not exist on a domain. Also known as a default address.

Certificate (Public Key Certificate)

An electronic document that states the identity of a server so that end users know that they communicated with the correct website.

Certificate Authority

An entity that issues digital certificates for server verification.

CGI (Common Gateway Interface)

A protocol that allows a web server to communicate with scripts and other software. cPanel’s CGI Center provides an array of CGI scripts that allow website owners to generate and manage useful features for websites (for example, guestbooks, clocks, hit counters, countdown clocks, and banner ads).

CGI Script Alias

A feature of Apache that creates the cgi-bin directory. This is a special directory that contains files that Apache knows to execute as CGI scripts.

Character Set

(Also sometimes known as “charset”). A code that pairs a sequence of characters with a set of numbers, which allows a computer to store and transmit the characters. ASCII is one popular character set. Several character sets exist for Cyrillic and Asian alphabets. For more information, read the Wikipedia article about character sets.

chmod (change mode)

A CLI command that allows you to set permissions to view, write, or execute a script.

CIDR (Classless Inter-Domain Routing)

A routing method that allows you to create routable subnets with finer granularity than the traditional network classes. CIDR notation is the combination of an IP address and an abbreviated subnet mask. This mask consists of a slash (/), followed by the number of bits (which is between 0 and 32). Larger numbers indicate smaller network segments. For example, the CIDR notation corresponds to an IP address of and a subnet mask of, with a total of eight addresses in the segment.

CLI (Command Line Interface)

A means of communication with a computer, in which you type commands. On Unix systems, this is also often called a shell.


Any application that accesses a service on another computer. Web browsers such as Internet Explorer can be called web clients. FTP clients include FileZilla and Cyberduck.


A group of linked servers. WHM allows you to create a DNS cluster, which keeps DNS records synchronized among a group of computers. This eliminates the need for manual updates.


A computer program that translates source code that was written by people into a language that is readable by a computer. As a security measure, WHM allows you to disable your web server’s compilers for most users.


Mail server software, known for its IMAP component. For more information, visit the Courier website.


Software that website owners can install on a website through cPanel. cPAddons provide useful tools to a website. Common examples include bulletin boards, chat programs, and online shopping carts.

CPAN (Comprehensive Perl Archive Network)

The main repository of Perl modules, which are pieces of Perl software. The CPAN library contains over 12,000 modules, most of which are free of charge. cPanel allows you to search CPAN and install Perl modules.


Companion software to WHM, designed to simplify website maintenance for website owners.

cPanel Packages

Pieces of software that are bundled together to allow you to archive and install them. cPanel packages, like FTP and MySQL software, can be updated in WHM's Update Preferences feature.


The cPanel daemon that provides access to the Web Disk feature.


A WHM feature that helps protect your web server from malicious users who try to gain unauthorized access through brute force attacks.


A copy of a user’s website, which you can create when you run the pkgaccount script. The cpmove file is useful as a backup and can be manually uploaded to restore the user’s web files.


cPanel Service Daemon, the software that runs cPanel on your server.

CPU Load

The amount of processing ability that programs on your server currently consume, measured as a percentage. For more information, view the Wikipedia article.

Cron Job

A command that is executed at regular intervals on a server. These commands are stored in the crontab Unix configuration file.

.crt File

An SSL certificate, which is an electronic document that ties a public key to a trusted entity. This electronic document is a key piece in the authentication process.

CSR (Certificate Signing Request)

A request that you send to a certificate authority for an identity certificate. cPanel can generate a CSR for you, but because authorities vary with regard to the information they require, you should check their requirements before you apply for a certificate.

CSS (Cascading Style Sheets)

A style sheet programming language that describes how a document, often written for the web in HTML, should appear.


The Common Unix Printing System Daemon, which the web server uses to print. This daemon is disabled by WHM's Quick Security Scan feature. We strongly suggest that you disable cupsd because it is vulnerable to attacks.

CVE (Common Vulnerabilities and Exposures) System

An archive of publicly known security threats, vulnerabilities, and exposures. The CVE system assigns numbers, known as CVE identifiers. These identifiers provide a reference point when you evaluate the coverage and effectiveness of security tools and services.




A computer program that runs as a background process, and so is not visible to, or directly controlled by, the user.

Data Center

A facility that is used to house servers. A data center is generally a safe place to keep a server because it typically includes backup power supplies, multiple communication connections, and environmental controls.

Default Address

The email address to which cPanel routes any email message that is sent to email accounts that do not exist at a domain. Also known as a Catch-All Address.


A term that is used to describe a feature that is no longer supported.

DHA (Directory Harvest Attack)

A technique that is employed by spammers, in which they attempt to find valid email addresses through guesswork and various permutations of common addresses.

Dictionary Attack

A method in which a malicious user tries to guess a password with words that are found in a dictionary. This attack is similar to a brute force attack.

Directory (Folder)

A repository for files, analogous to a file folder on a personal computer. In website management, a directory will contain the website's files.

Disk Space Quota

A limit that is placed on the amount of disk space that an account is allowed to use.

DKIM (Domain Keys Identified Mail)

The replacement for the older DomainKeys protocol. Like DomainKeys, DKIM attempts to verify the origins of email messages.

DNS (Domain Name System)

The component of the Internet that acts as a “phone book,” and converts human-readable domain names (for example, into computer-readable IP addresses (for example,, in the case of

DNS Zone

An administrative space or portion of the Domain Name System. This space directs web traffic to the correct location. An example is, a DNS zone whose servers direct its web traffic.

DNS Zone File

A file on your server that primarily maps IP addresses to domain names. A correctly configured zone file must exist in order for visitors to access your server from the Internet.


A program that manages DNS services and clustering.


The name that a site owner gives to a website, which will appear in the website’s URL and email addresses. It is usually seen as, where example is the domain name.

Domain Forwarding

A technique that allows you or your users to automatically send visitors to a domain when they access another domain. For example, a user may reach when they type See also redirect.


An email authentication method that attempts to verify that a message actually came from the domain that it appears to have come from.


Mail server software that is designed for optimal security. For more information, visit the Dovecot website.

DSA (Digital Signature Algorithm)

A method that you can use to generate public and private keys for the encryption of data. This algorithm was developed by the U.S. government.



Entropy Banner Manager

A script that is included with cPanel and that allows you to manage rotating banner images on your website.

Entropy Search

A script that is included with cPanel and that creates a search engine for your website.

Environment Variables

Values that advanced administrators place within specific files on the server to change the behavior of Apache and PHP. For more information, read our EasyApache documentation.

Error Pages

These pages display warning messages when visitors encounter problems while they try to access your site. cPanel allows you to configure the error messages that display for your site. For more information, read our HTTP Error Codes and Quick Fixes documentation.


Mail server software that is known for its configurable nature. For more information, visit the Exim website.




An option that you can use to handle mail that is received by the default or catch-all email addresses of cPanel users. The fail option returns as undeliverable all mail that is received by the default address.


In cPanel, a tool that processes mail based on your preferences. For example, a filter can automatically discard spam or save mail from a specified sender to its own folder. In cPanel, filters can be applied to the main email account on a domain (Account Level Filters), or customized for each individual account (User Level Filters).

Forceful Reboot

One of the two methods that you can use to restart your server. This forces the server to restart regardless of any error(s) it may have encountered. You should only use a forceful reboot if you cannot reboot gracefully, because it may cause data loss.

FormMail Clone

Software that imitates the function of FormMail. FormMail creates an email message from data that a user enters into the text boxes on a web page, and sends the message to the intended recipient.


A tool that allows you to forward a copy of every email message that you receive to another address. When a forwarder is set up, you will still receive mail at the original recipient address. If, however, you create a forwarder before you create the original address, messages will be forwarded to the end address but will not be sent to the original address, because it does not exist.

FQDN (Fully Qualified Domain Name)

A name that uniquely defines a domain’s location. It is usually seen as with a trailing dot. For the purposes of cPanel, a final dot is not necessary, but the domain name must contain at least two dots. FQDNs must be written in lowercase letters.


A Microsoft® application that allows site owners to edit a web page in WYSIWYG (“what you see is what you get”) format, rather than raw HTML code and CSS. WHM provides FrontPage extensions, so that site owners can publish their sites with FrontPage, which allows them to skip the FTP process.

FTP (File Transfer Protocol)

A method that you can use to transfer files from one computer to another. cPanel & WHM software comes equipped with an FTP server that can be configured to the website owner's preference. An FTP client must be installed on the local computer in order to send files to and receive files from the FTP server. Some FTP clients include FileZilla (for Windows®, Linux, and Unix), and Cyberduck (for Mac®).




A piece of software in the Ruby language. The central repository for these pieces of software is called RubyGems. For more information, visit the RubyGems website.

Generators (web stats)

Pieces of software that will compile statistics for your web server. For example, they can tell you how much bandwidth has been transferred per domain. Three generators can be configured through WHM: Analog, AWStats, and Webalizer.

Gigabyte (GB)

A unit of measure for digital memory storage. One gigabyte is equal to 1,024 megabytes, 1,048,576 kilobytes, or 1,073,741,824 bytes.

GnuPG (GNU Privacy Guard)

A suite of tools that you can use for data encryption and signing. These tools are most commonly used for signing emails. For more information, visit the GnuPG website.

Graceful Reboot

The preferred way to restart your server. This method stores new system information before the server shuts down.


A program that compresses files for disk space conservation, minimizes transfer times, and makes the transfer of multiple files easier. The compressed files use the filename extension .gz. In Unix and Linux systems, gzip is often used with tar to create a “tarball” file (which ends with .tar.gz).



Home Directory

A cPanel account’s highest-level directory, which contains all the files and directories that are used by websites that the account manages. Files that are placed in a home directory are not viewable online unless they reside in the public_html directory or a subdirectory of public_html.

Horde Webmail

A webmail client that is included with WHM. A webmail client allows users to check email through a web browser.


The unique, human recognizable name by which a server will be known across the Internet. For example, You can specify or change your server’s hostname with WHM’s Hostname feature. The server hostname is distinct from your domain name.

Also known as an “inline link.” A hotlink is a direct link that embeds a file (such as an image or video) from your site into another website. When another site embeds your files, it uses your bandwidth to serve those files.


A file that resides in a specific directory, and contains configuration information that applies to that directory. The .htaccess file may also contain authentication instructions.

HTML (Hypertext Markup Language)

The language in which most pages on the World Wide Web are written.


A file that resides in a specific directory, along with a .htaccess file. The .htpasswd file contains encrypted password information when authentication has been set up for the directory.

HTTP (Hyptertext Transfer Protocol)

The method (protocol) by which you transfer data over the Internet.


The configuration file for the Apache web server. For more information, visit the Apache website.




An instant messaging service. You may choose to receive updates from your server through ICQ. For more information, visit the ICQ website.

IMAP (Internet Message Access Protocol)

Along with POP3, IMAP is one of the two most widely used email transfer methods. IMAP synchronizes email account information with the mail server on a regular basis. If a user logs in to multiple computers to check email, IMAP will allow the user to see which messages they have viewed, replied to, forwarded, etc. POP3 does not display this information.

Include (file)

A file that is automatically included within another file by the program that reads it. In WHM, includes pertain to a series of specifications that can be added to your Apache configuration file (httpd.conf) through the include command.

Index Page

The page, most often titled index.htmlindex.htm or index.php, that is viewed by default when a visitor accesses a directory of a website. If no index page exists for the specified directory, the visitor will see a list of files in that directory, unless indexing is disabled in cPanel.


A full-featured ecommerce application server that will allow you to conduct business online, and that grants your users a virtual shopping cart, payment method, and more.


A loader that, if enabled, can load PHP for cPanel. For more information, visit the IonCube website.

IP (Internet Protocol) Address

A number that identifies a computer on a network, which makes it possible for other computers to find and communicate with it.

IRC (Internet Relay Chat)

A method of real-time online communication that allows both group discussion and one-to-one messaging, as well as data transfer.



Jailed Shell

A CLI configuration that restricts users’ access rights. Shell sessions are limited to a filesystem that does not contain the home directories of other cPanel users on the system.


A computer programming language that is used by many web applications. cPanel uses the Java language to provide the SSHTerm and Java Telnet features. These small applications, which run within the context of a web browser, are called applets.




A central component of your server’s operating system. The kernel manages communications between the user and the server’s resources, such as its processor and the memory.


In cryptography, a key is used to encrypt or decrypt information. Keys are an important part of encryption and security and should be guarded appropriately. A key file is saved with the .key filename extension.

Kilobyte (KB)

A unit of measure for digital memory storage. One kilobyte is equal to 1,024 bytes.




A visitor who uses another person’s password to access a restricted area of a website. cPanel allows you to redirect likely offenders or disable accounts with compromised passwords in order to prevent leeches.


A term for an old software program or computer system that is still in use.


The part of a system that loads a program. In WHM, you can use the Tweak Settings interface to choose the loader that cPanel uses for PHP.

Local Host

A way to refer to the computer that you currently work on.

Local User

A user who accesses a service on the machine on which the service is located, as opposed to remotely. When you select this option from the Tweak Settings interface, it allows a cPanel user to set up an email address that will receive any mail sent to an invalid address at his domain.


A file that is automatically created by the server and that records activities that are performed by specific programs and applications on the server. For example, error logs are lists of errors that visitors have encountered on a website that are generated by Apache.

Log Files

See also the definition of Log, above. The following list includes many of the log files that you will encounter when you use cPanel & WHM software:

  • access_log — A file that contains a record of the IP addresses of visitors that have accessed sites hosted by your server. This file can be found at /usr/local/apache/logs/access_log.
  • cpdavd_error_log — A file that contains a record of errors that were encountered by cpdavd. This file can be found at /usr/local/cpanel/logs/cpdavd_error_log.
  • cphulkd_errors_log — A file that contains a record of errors that were encountered by the cPHulk daemon, cphulkd. This file can be found at /usr/local/cpanel/logs/cphulkd_errors.log.
  • error_log — A file that contains a record of errors that were encountered by the Apache web server. This file can be found at /usr/local/apache/logs/error_log.
  • license_log — A file that contains a record of errors that were encountered when cPanel checked its license. This can be found at /usr/local/cpanel/logs/license_log.
  • login_log — A file that contains a record of failed login attempts. This file can be found at /usr/local/cpanel/logs/login_log.
  • stats_log — A file that contains a record of the activities of cpanellogd, the daemon that compiles your server’s web statistics. This file can be found at /usr/local/cpanel/logs/stats_log.
  • tailwatchd_log — A file that contains a record of errors that were encountered by tailwatchd, the daemon that monitors your server’s logs. This can be found at /usr/local/cpanel/logs/tailwatchd_log.

A web analytics program that delivers information about your website's traffic, keywords, and content. For more information, visit the Logaholic website.



Mail Transfer Agent

A program that sends and receives email messages. Also known as a message transfer agent.


A format that stores email as individual messages with unique filenames. Maildir is the default mail storage format. See also mbox.

Mailing List

A list of email addresses that mailing list members can use to communicate. Alternatively, such a list can be used to send email messages to a large group of people. cPanel & WHM software uses the Mailman program for mailing list software. For more information, visit the Mailman website.


Mailing list software that sends email messages to a group of specified email addresses. For more information, visit the Mailman website.


A legacy format that stores email messages bundled together as a single file. This format has been replaced by Maildir. See also Maildir.

Megabyte (MB)

A unit of measure for digital memory storage. One megabyte is equal to 1,024 kilobytes, or 1,048,576 bytes.

MIME (Multipurpose Internet Mail Extensions) Type

Now called an Internet media type, this component of a file identifies the file type, so that web browsers know how to handle it. cPanel allows you to specify which application should be used to open files with a given extension.


A feature of Apache that allows visitors to type your hostname, a tilde (~), and the website owner's username in order to view a website (for example, You should disable mod_userdir in WHM's Security Center, because the bandwidth that is used when the site is accessed by this method is attributed to the web host’s main domain, and skips bandwidth monitoring systems. For more information, visit the Apache website.


In encryption algorithms like RSA, the modulus is the number that both the private and public keys have in common. The plural of modulus is moduli. You can view a key’s modulus in WHM's SSL Storage Manager interface.


In general computing, to mount a file system means to make it accessible to users. In a Unix or Linux operating system, mount can be used as a command to tell the operating system that a file system or device is ready to use and to affix that system or device to a certain directory.

MRTG (Multi Router Traffic Grapher)

Software that allows you to monitor network traffic. For more information, visit the MRTG website.

MX (Mail eXchanger) Entry

A record that specifies where email should be sent for a domain, as it contains the mail server’s IP address. When you use an email scanning service or custom mail delivery, the server administrator may need to change the MX record for a domain in WHM's Edit MX Entry feature.


A relational database management tool and server, as well as the type of database it manages. Databases are an integral part of web applications, such as bulletin boards and blogs. cPanel provides an integrated MySQL interface as well as a MySQL database editing tool called phpMyAdmin. Server administrators can manage MySQL database services in WHM's SQL Services section.




The most prominently used DNS server software on the Web. Also referred to as “BIND.”


A piece of software that obtains DNS information from a physical nameserver, which is a computer that contains a list of domain names and their IP addresses. These computers are spread through the Internet and allow visitors to access a domain through its IP address. Nameserver software gathers data about domains over time. Because of this, changes to DNS records can take up to a week to reach all of the nameservers on the Internet (“propagate”).

NFS (Network File System): 

Allows users to access remote files as though the hardware that they access to manipulate the file was attached directly to the local machine. WHM's Quick Security Scan feature disables this daemon.

nfs statd

A process that is used to mount NFS file systems. WHM's Quick Security Scan feature disables this daemon.

nis (Network Information Service)

A directory protocol that distributes information across or within networks. WHM's Quick Security Scan feature disables this daemon.


This is a Unix or Linux system account with the UID of 99. This system account is used to execute CGI and PHP scripts if SuEXEC and PHPsuExec are disabled. EasyApache no longer supports the PHPsuExec configuration.


DNS server daemon. For more information, visit the NSD website.



Open Relay

A mail server configuration that allows anyone to send mail through the server. For security reasons, do not allow your server to operate as an open relay.


A feature that uses PHP to deny users the ability to open files that are outside their home directories. You can enable this in WHM’s PHP open_basedir Tweak interface.

Option Module (“opt mod”)

An Apache configuration option that advanced administrators can add to the EasyApache (Apache Update) interface.



  1. The set of resource limits that are assigned to a user’s account. You can create, edit, and delete packages in WHM's Packages interface.
  2. A collection of software that is bundled together for distribution and installation. cPanel provides various third-party software, such as FTP and MySQL, as RPM packages that are then managed by the rpm.versions system. For more information, read our rpm.versions documentation.
Parked Domain

A second domain that points to a primary domain. When users attempt to access the parked domain, they will see the main website. For example, both and go to the same place, because is a parked domain for

PASV (Passive Mode)

A mode for FTP connections that will initiate connections from the client side. You may wish to use this mode if a user has problems when they attempt to connect to an FTP server through a firewall.

PEAR (PHP Extension and Application Repository)

A repository of PHP code. cPanel allows you to search for and install PEAR packages that consist of PHP programs, which can perform useful functions for your website.

PECL (PHP Extension Community Library)

A repository for C extensions (pieces of software) that are designed for use in PHP. For more information, visit PHP's PECL website.


Known for its ability to process text, Perl is a useful language for web applications. Perl applications are commonly found as, and .cgi files and may require Perl modules. Perl modules can be installed from cPanel's Perl Modules interface or WHM's Install a Perl Module interface.

Perl Module

A piece of software that is written in the Perl language. Modules are common pieces of software that are reused often. For example, a user who uses a calendar module will not need to write a set of functions to display calendars.


A computer scripting language in which many web-based applications are written. PHP applications are commonly found with the filename extensions .php.php4, or .php5. Some PHP applications require PEAR packages, which can be installed in cPanels PHP PEAR Packages interface or in WHM's Module Installers interface.

PHP Package

A piece of software that is written in the PHP language.


A graphical application that allows server administrators to manipulate and manage MySQL databases over the Internet. For more information, visit the phpMyAdmin website.


Like suEXEC for CGI, PHPsuExec allows users to execute PHP code under their own user IDs. By default, PHP is executed by the system account known as nobody with the UID of 99. EasyApache no longer supports this configuration.

PID (Process ID)

A unique number that your server assigns to each process that runs.

POP before SMTP

An authentication method for mail servers that will allow a user who has received mail through POP3 or IMAP to send mail for 30 minutes without the need to reauthenticate through SMTP.

POP3 (Post Office Protocol version 3)

Along with IMAP, one of the two most widely used email transfer methods. POP3 copies every message in an email account to a local computer and removes it from the mail server. No information is sent back to the email account about message replies, forwarding, etc. If an account owner uses multiple computers to check email, it is advisable to use IMAP instead of POP3.


A service that maps program numbers to network addresses on a server. Often seen as rpc.portmap or portmap. This service is not widely used. It is disabled by WHM's Quick Security Scan feature.

POSIX (Portable Operating System Interface)

A standardized collection of commands for the Unix operating system.


A database management system, much like MySQL. For more information, visit the PostgreSQL website.

Private Key

A string of characters that a computer uses to encode or decode the encrypted messages that it receives. Encryption schemes use a pair of keys (one public, one private) to create a secret code so that anyone who looks at messages that are sent from or received by your computer will be unable to determine the contents of those messages without access to the private key. A private key protects your confidential information and should be safeguarded appropriately.


An instance of a program that runs on your machine.


One of two FTP servers that are included in your installation of WHM. The other is Pure-FTPd. For more information, visit the ProFTPd website.


The spread of a website’s DNS information across the Internet.


Short for "proxy server." This server receives requests from users and forwards those requests to other servers.

Public Key

A string of characters that a computer uses to encode or decode the encrypted messages it receives. Typically, a public key will be placed on a server so that you can establish an encrypted connection to that server.


A subdirectory, located inside of your home directory, that contains files that are publicly accessible through FTP. FTP users may also upload files to this directory. This is the default directory that users will access when they connect to your site through anonymous FTP.


A subdirectory, located inside the home directory, that contains files that are publicly accessible through HTTP. The www directory is a link to public_html. Any files and folders that are inside of public_html are visible over the Internet, unless the website owner specifically protects them with password protection or the .htaccess file.


One of two FTP servers that are included in your installation of WHM. The other is ProFTPd. For more information, visit the Pure-FTPd website.


A programming language that many applications use. When you encounter this term in WHM's Update Preferences interface, it refers to the Python interpreter, which must be installed on your server before it can run Python programs. For more information, visit the Python website.




Limits to the amount of disk space that a user is allowed to use. In order to set up quotas for your users, you must first use WHM’s Initial Quota Setup feature.



Raw Opts

Also known as “custom configure flags." Lines of data that advanced users can add to a specific file on the server in order to customize the configuration of Apache. For more information, read our EasyApache documentation.

RBL (Realtime Blackhole List)

A list of mail servers that are known to send spam. You are able to subscribe to the list and block incoming mail from such mail servers in WHM's Exim Configuration Editor.


A feature that sends users to a different domain than the one they attempted to access. For example, a user may reach when they type cPanel allows website owners to set up either temporary or permanent redirects. See also domain forwarding.


A web page that links to a site; also called an “HTTP referer.” This spelling is the industry standard term, though it is based on a misspelling of “referrer.”

Regular Expressions

Often seen as regex or regexp. Regular expressions are a means by which you can format text so that a specified program can process it and use it to search in a prescribed way. A wildcard character such as an asterisk (*) is an example of a regular expression.


A user who forwards email to a secondary destination. WHM’s View Relayers feature allows you to view users on your server who have relayed mail.

Release Tiers

These exist in four types which are, in order from least to most stable, EDGE, CURRENT, RELEASE, and STABLE. For more information, read our cPanel & WHM Product Versions and the Release Process documentation. 


In web hosting, resellers take a large amount of resources (bandwidth and disk space) on your server and sell those resources in smaller packages to individual cPanel account holders.


The client side of the DNS system. Resolvers are programs that process DNS queries and work to obtain an IP address from a human-recognizable URL. In Unix and Linux, the file /etc/resolv.conf usually points to a server’s resolvers.


In computing, a rollback involves the restoration of any part of a system to a previous configuration.

  1. Specific to Unix and Unix-based systems, the system account. This account is used by a system administrator and carries full privileges to configure a computer system. Also called “superuser.” 
  2. The highest level directory in a Unix or Unix-based system, usually notated by a forward slash (/).
Root Language File

A file that supplies the words for your cPanel interface when a needed term in the interface does not appear in the primary language files. The root language file is located in the /usr/local/cpanel/lang directory. The primary language files are located in directories specific to their themes (for example, /usr/local/cpanel/base/frontend/x3/lang).

RoundCube Webmail

A webmail client that allows users to check email through an Internet browser rather than an email client.


The Red Hat® Package Manager. “RPM” can refer to either the file format or the software that is packaged within that format.


An algorithm that generates public and private keys when you wish to send encrypted data between a local machine and a remote machine. The name of this method is not an abbreviation; it is named after its three inventors.


A package manager and program library for the Ruby programming language. Also see Gem. For more information, visit the RubyGems website.



SCP (Secure Copy Protocol)

A method by which you can transfer encrypted files from one computer to another. This method prevents the interception of data.

Script Hooks

A program that is triggered by some event. WHM's EasyApache (Apache Update) interface allows you to embed custom hook scripts into the Apache configuration process.

Server Contact

The server administrator whose contact information is entered in WHM's Basic cPanel & WHM Setup interface.

/server-info and /server-status

These pages contain general information about the server. You can use WHM's Tweak Settings interface to configure which users are allowed to view this information.

Service Manager

In computing, a piece of software that monitors the processes and services on a machine. WHM’s Service Manager feature allows you to enable and disable services.


Software that allows a user to interact with a computer. Many Unix shells allow the user to type commands, and are often referred to as CLIs, or command line interfaces.

Shell Fork Bomb (Protection)

A shell fork bomb is a malicious process that creates a cascade of new processes in order to use a server’s system resources, which, in effect, crashes the server. WHM offers a protective service from shell fork bombs.

Shopping Cart

A piece of software that is used on web servers that handle ecommerce. A shopping cart allows the shopper to hold items that they wish to purchase while they continue to shop on the website.


A link to an application that allows you to access it from a convenient location, like your computer’s desktop.

Skeleton Directory

A directory that defines which files and subdirectories new accounts will have by default. When the account is created, the new user’s account will contain an exact copy of the skeleton directory.


A smarthost is a type of mail relay server. A smarthost permits an SMTP server to send emails to an intermediate mail server before it sends messages to their final destination.

SMTP (Simple Mail Transfer Protocol)

This protocol is the standard by which you transmit email messages across the Internet. It is namely used to send mail to a mail server’s relayer.

SourceGuardian/OldSource Guardian

PHP loaders that utilize a binary bytecode and, sometimes, multiple levels of encryption. For more information, visit the SourceGuardian website. You can use WHM's Tweak Settings interface to select a PHP loader.


Chiefly, unsolicited email that is sent in bulk, usually by an automated system. Because spam is considered a costly nuisance to the recipient, cPanel includes features like SpamAssassin and BoxTrapper that can cut down on the amount of spam that you receive. Server administrators can use WHM's Tweak Settings interface to enable these services for their users.


An application that can filter suspected spam. SpamAssassin can be configured to filter spam more or less aggressively, based on the user's needs. For more information, visit the SpamAssassin website. Server administrators can use WHM's Tweak Settings interface to enable this service for their users.

SPF (Sender Policy Framework)

A feature that allows a recipient server to verify that an email message has really been sent from the domain specified in the From: field. Enable SPF to prevent your server replies to spam that has forged your domain name as part of the sender’s address. SPF only works if both the sending and receiving mail servers have SPF enabled.


An attack in which attackers appear as another user through the falsification of data, in order to conceal their identities. Enable SPF to make it more difficult for spammers to spoof a domain.


A type of file that can incorporate several different images. Sprites are used to speed up the load time of the cPanel interface. When you add an icon, cPanel will add it to the appropriate sprite file. If your icon is not displayed properly, click Generate Sprites in the Branding Editor to cause the sprite file to upload properly.

SQL Database

A type of relational database management system. WHM is compatible with MySQL and PostgreSQL.

SquirrelMail Webmail

A webmail client that allows users to check their email through Internet browsers.

SSH (Secure Shell)

A network protocol that allows a user to log in to a remote machine securely. cPanel & WHM software can create keys to authenticate a user's identity during SSH login, and lets users manage SSH keys.

SSL (Secure Sockets Layer)/TLS (Transport Layer Security)

TLS is a more recent version of SSL. Both are cryptographic schemes that allow for secure interaction between a web browser and a web server. All sensitive data (credit card numbers, login information, etc) that is transmitted over the Internet should be protected by SSL/TLS. Website owners can install an SSL certificate on a website (in WHM's Install a SSL Certificate and Setup the Domain feature) to allow the site to be protected by SSL/TLS.

SSL Certificate

An electronic document (with the filename extension .crt) which binds a public key to an identity that consists of an email address, company, and location. This electronic document is a key piece in an authentication process.


A free program that is used to provide universal SSL/TLS tunneling services. A tunneling service allows computers to communicate with each other directly through SSL/TLS protocols.


Also known as a “skin,” the style contains the graphics that determine the appearance of a user’s cPanel interface.


A subsection of a website that exists as a subdirectory in the website owner's home folder. If the domain were, then the subdomain URL would appear as


A feature provided by Apache that allows users to run CGI and SSI applications on the system as themselves. By default, CGI and SSI are executed by the system account that is known as nobody and has the UID of 99.




Originally derived from “Tape Archive,” a program that collates files for transfer or distribution. Files processed by this program are usually compressed, commonly called “tarballs,” and use the filename extension .tar. Due to the compression commonly used, .tar often precedes the .gz file extension.


A file collated by the tar program, and usually compressed.


A network protocol that allows a user to log in to a remote machine user account remotely. Telnet is similar to SSH, but less secure. Telnet should not be used to connect to your web site except for testing purposes. Login information is sent through Telnet as plain text and can be easily intercepted.


In cPanel software, the theme is the larger, skeletal frame work to which the style or ‘skin’ will be applied.


A version of an image file that is reduced in size, which allows you to easily view multiple images. cPanel includes a Thumbnailer tool as part of its Image Manager section.


A cPanel tool that automatically sizes down all the images in a directory. The new thumbnails are stored in a subdirectory named */Thumbnails, where * is the parent directory that contains the original images.

Time to Live

Often abbreviated as TTL, it specifies how long a particular record should be kept in memory before it should be deleted. This is most often used within DNS.


A small box of information that will hover above an icon when the cursor points at it. This is common through cPanel and WHM as well as many other GUIs. In the WHM Locales interface, this term defines the language of the text that is within the tooltip information box.

Trojan Horse

Also known simply as a trojan, a Trojan horse is a piece of software that claims to perform one function but actually performs malicious functions secretly.

Trust Key Relationship

A cryptographic scheme that involves a public and private key pair.



UDP (User Datagram Protocol)

A connectionless transport protocol that works in conjunction with the Internet Protocol. UDP transfers small units of data that require little reassembly, because it does not transmit data packets in a sequential order. It is used primarily to broadcast messages over a network.

UID (User ID)

The unique user number that any user on your server will be assigned during a session. The following list includes some important UIDs:

  • 99 — nobody — The default executor of CGI scripts if suEXEC is disabled.
  • 0 — root — The top-level system user.



Unix Time

Unix time is measured by the number of seconds that have passed since the 1st of January, 1970 UTC.


A web statistics analysis program that was made by Google. For more information, see the Urchin website.

URI (Uniform Resource Identifier)

On the web, a URI is a string of characters that identifies a website. URI is often used synonymously with the terms “URL” and “web address,” although there are technical differences among the three.

URI Encoding

Encodes information within a Uniform Resource Identifier (URI). Characters that are usually reserved for the URL must be converted to percent-encoded characters so that they can be used within a URL (for example, the forward slash (/) is encoded as %2F). For more information, visit URL Encoding at W3Schools.

URL (Uniform Resource Locator)

On the web, a URL is a string of characters that identifies the location of a website. Because IP addresses are difficult to remember, URLs are used instead. For example, it is much easier to remember to go to than URL is often used synonymously with the terms “URI” and “web address,” although there are technical differences among the three.


A person who uses a computer to accomplish some purpose.




A method of hosting multiple domains on a single server and sometimes on a single IP address. For more information, visit the Wikipedia article on VirtualHost.


A person who views your website.



Web Browser

An application that is used to view and interact with sites and pages on the World Wide Web. Examples include Firefox®, Internet Explorer®, and Safari®.

Web Disk

A feature of cPanel that lets website owners manipulate web files by dragging and dropping, just as one would on a local computer’s operating system.

Web Root

The top-most directory of your website (public_html or www), inside which all of the files and subdirectories for your website reside.

Web Server

A program, such as Apache, which receives requests from clients (web browsers), retrieves the requested web pages, and “serves” them to the clients.

Webalizer, The

A program that displays various statistics for a website in tables and graphs. For more information, visit the Webalizer website.


Any application that allows website owners to access email through a web browser. The main advantage to webmail is the ability to access the email account from any computer that is connected to the Internet without the need to install or configure a specific mail program.

Wheel Group

This group of users is allowed to execute the su command on a Unix-based system, which allows them to become the root user. This command requires the password for the root user.

WHM (WebHost Manager®)

Companion software to cPanel that is designed for web hosts, resellers, and system administrators.


A Unix or Linux command that can be executed in a terminal session in order to find out who owns a domain. For example, whois will return the ownership information for cPanel.


For the purposes of cPanel, www is a link to the directory that holds the files that make up your website ( /public_html).



X-source Headers

Pieces of information that are added to email messages sent from a PHP script on your server, which detail the script’s location. Enable these headers to help you locate insecure email scripts that have been abused by spammers. You can enable these headers in WHM's Tweak Settings feature.

XSRF Attack (Also, CSRF)

XSRF and CSRF stand for Cross-Site Request Forgery. To exploit a trusted website, this attack forces a user to execute unauthorized commands, usually through a hyperlink. To help prevent XSRF attacks, cPanel & WHM software requires every request to contain your unique per-session security token.






A DNS zone; an administrative space or portion of the Domain Name System. This space directs web traffic to the correct location. An example is, a DNS zone whose servers direct its web traffic.

Zone file

A DNS zone file; a file on your server that primarily maps IP addresses to domain names. A correctly configured zone file must exist in order for visitors to access your server from the Internet.