Glossary of Terms

“A” (Address) Entry: A record, residing on your server, that contains your server’s hostname and IP address. The “A” entry is essential because it tells DNS servers the identity of your server, allowing visitors to find your server on the Internet.

Account: A record for accessing privatized information. For example, your cPanel account lets you manage your website. In cPanel, other instances of the term “account” occur in email and FTP.

ACLs (Account Creation Limits): When you create reseller accounts in WHM, these are the constraints you place on the resellers’ privileges.

Account-Level Filter: A rule that determines where email, delivered to a domain’s main email account and meeting certain criteria, will be delivered. See also Filter.

Addon Domain: An additional domain name associated with a cPanel account. Each addon domain is stored in its own directory that 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 to properly function.

Addons (cPAddons): Additional services, usually provided by cPanel, for your users. Some examples of addons are blogs, message boards, and shopping carts.

AIM (AOL Instant Messenger): A widely used instant messaging program. WHM can notify you via AIM if there is a problem with your server. More information about AIM can be found at

Analog: A program that provides information about the visitors to a website in both graphical and statistical views. More information about Analog can be found at

Anonymous FTP: A process whereby visitors without FTP accounts may upload and download files to and from a website. Although it poses security risks, anonymous FTP can be convenient if the site owner wishes to make files publicly available for downloading. When setting up anonymous FTP, it is important to protect any sensitive information by changing file permissions and directory access permissions.

Apache: A program that receives requests from web browsers and responds by “serving” web pages to the browsers. For this reason, it’s called web server software.

Apache Handler: A means of telling the Apache software how to process a given type of file. By default, Apache only handles certain file types. You can configure Apache handlers for other file types using cPanel. For more information, see Apache’s handler documentation.

ASCII (American Standard Code for Information Interchange): A common character set based on the English alphabet.

atd: A daemon for the at command in Linux operating systems, which performs scheduled tasks. This daemon is disabled by the WHM Quick Security Scan feature.

Authentication: A process for confirming 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/private key pair.

Autoconfig: A process that sets up a user’s Outlook® or Outlook Express account to receive their cPanel email. You can enable or disable this feature using WHM’s Enable/Disable Outlook® Autoconfig? feature. This feature is available in WHM versions up to 11.32.

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

AWStats (Advanced Web Statistics): A program that provides information about the visitors of a website. This information is presented in both graphical and statistical views. More information about AWStats can be found at

Backscatter: Bounce email messages (or failed Delivery Status Notifications) erroneously sent to a domain whose name has been forged as the sender of spam. Using SPF on your mail server should reduce backscatter.

Backup: A copy of your website’s files, directories, databases, and email configurations. Keeping a backup copy of your website on your personal computer is a wise precaution.

Bandmin: Bandmin is a set of Perl scripts that monitor and log bandwidth usage by IP. You can access Bandmin at the following location: (where is your domain name).

Bandwidth: The amount of data 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 these files transferred to visitors’ computers. Hosting providers often limit a site owner’s bandwidth, as it can affect the performance of the server.

Bandwidth Limit: A limit imposed on the amount of data an account is allowed to transfer per month.

Bayes Testing (aka Bayesian Spam Filtering): Bayesian spam filtering is a method of filtering spam based on statistics. This method uses tokens, generally words, found in emails to determine whether an incoming message is spam. This filtering technique relies on Bayesian statistics. Bayesian classifiers calculate a probability that an email is or is not spam by correlating the use of tokens with spam and non spam emails.

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

BIND (Berkeley Internet Name Domain): The most prominently used DNS server software. Also referred to as named. More information about BIND can be found at

Blackhole: An option for handling mail 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 can result in more spam being sent to your users, and it places a larger load on your server than the “fail” option.

Blocker: 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 11.30.

Bounce Message: An email reply informing a sender that there was a problem delivering an email.

BoxTrapper: An application included with cPanel that filters spam by requiring would-be senders to reply to a verification email (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 upon receipt of mail from a blacklisted address. See also BoxTrapper Ignore List and BoxTrapper Whitelist.

BoxTrapper Ignore List: A list of email addresses from which incoming mail will be blocked. cPanel does not send a warning message upon receipt of mail from an address ignored by the BoxTrapper application. See also BoxTrapper Blacklist and BoxTrapper Whitelist.

BoxTrapper Whitelist: A list of email addresses from which incoming mail will automatically be accepted by the BoxTrapper application. See also BoxTrapper Ignore List and BoxTrapper Blacklist.

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 lets you lock out brute force attackers after a specified number of failed attempts.

Build: Formerly, a minor version of cPanel. These are now referred to as Release Tiers.

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 using WHM’s Install a SSL Certificate and Setup the Domain feature, or the Manage Service SSL Certificates feature.

Cache: A stored piece of information to which the server refers instead of accessing the information source, to save bandwidth and time. In WHM, you can configure caching of DNS records using the Edit DNS Zone feature. You can configure caching of disk usage data via the Tweak Settings page.

Catch-All Address: The email address to which cPanel & WHM routes any email message sent to email accounts which 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 the end user knows that he or she is communicating with the correct website.

Certificate Authority: An entity that issues digital certificates for server verification.

CGI (Common Gateway Interface): A protocol that lets a web server communicate with scripts and other software. cPanel’s CGI Center provides an array of CGI scripts that let website owners generate and manage useful features for websites, including a guestbook, clock, hit counter, countdown clock, and banner ads.

CGI Script Alias: A feature of Apache that creates a directory named cgi-bin. This is a special directory containing files which 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, allowing a computer to store and transmit the characters. ASCII is one popular character set; several character sets exist for Cyrillic and Asian alphabets. More information about character sets can be found at

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 assigns each Internet user to a four-part IP address, with each part separated by a decimal, followed by a slash and a number between 0 and 32.

CLI (Command Line Interface): A means of communicating with a computer by typing commands. On Unix systems, this is also often called a shell.

Client: 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.

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

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

Courier: Mail server software, known for its IMAP component. More information about Courier can be found at

cPAddons: Pieces of 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, pieces of Perl software. The CPAN library (located at contains over 12,000 modules, most of which are free of charge. cPanel allows you to search CPAN and install Perl modules.

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

cPanel Packages: Pieces of software that are bundled together for archiving and installation. cPanel packages, such as FTP and MySQL software, can be updated using the WHM Update Config feature.

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

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

cplog: Also known as error_log, a file that contains a record of errors encountered by the Apache web server. This file can be found at /usr/local/apache/logs/error_log.

cpmove: A copy of a user’s website created by running a script called pkgaccount. The cpmove file is useful as a backup and can be manually uploaded to restore the user’s web files.

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

CPU Load: The amount of processing ability currently being consumed by programs on your server, measured in a percentage.

Cron Job: A command on a server, executed at regular intervals. These commands are stored in a Unix configuration file called crontab.

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

CSR (Certificate Signing Request): A request, which you send to a certificate authority, for an identity certificate. cPanel can generate a CSR for you, but since authorities vary with regard to the information they require, you should check their requirements before applying 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.

cupsd: Common Unix Printing System Daemon, used by the web server for printing. This daemon is disabled by the WHM Quick Security Scan feature. We strongly suggest disabling cupsd as 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 evaluating the coverage and effectiveness of security tools and services.

Daemon: A computer program that runs as a background process, rather than being visible to, and directly controlled by, the user.

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

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

Deprecated: A term used to describe a feature which is no longer supported.

DHA (Directory Harvest Attack): A technique employed by spammers whereby they attempt to find valid email addresses through guesswork, using various permutations of common addresses.

Dictionary Attack: A method whereby a malicious user tries to guess a password using words found in a dictionary. 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 placed on the amount of disk space 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 which acts as a “phone book,” converting human-readable domain names (such as into computer-readable IP addresses (such as, in the case of

dnsadmin: A program that manages DNS services and clustering.

DNS Zone: An administrative space or portion of the Domain Name System. This space is responsible for directing 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.

Domain: The name a site owner gives a website, which will appear in the website’s URL and email addresses. Usually seen as, where example is meant for 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 by typing See also redirect.

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

Dovecot: Mail server software designed for optimal security. More information can be found at

DSA (Digital Signature Algorithm): A method of generating public and private keys for encrypting data. This algorithm was developed by the U.S. government.

EIDE (Enhanced Integrated Drive Electronics): A method for connecting hardware to a computer. WHM’s Optimize EIDE Hard Drives? feature can speed up communications between your server and external hard drives connected by EIDE.

Entropy Banner Manager: A script, included with cPanel, that lets you manage rotating banner images on your website.

Entropy Search: A script, included with cPanel, 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.

Error Pages: These pages display warning messages when visitors encounter problems while trying to access your site. cPanel lets you configure the error messages that display for your site. For an in-depth look at HTTP error codes, please visit our HTTP error codes documentation.

Exim: Mail server software, known for its configurable nature. More information about Exim can be found at

Fail: An option for handling mail received by the default or catch-all email addresses of cPanel users. The fail option returns as undeliverable all mail received by the default address.

Filter: In cPanel, a tool that processes mail according to 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: 1 of 2 methods for restarting your server. This forces the server to restart regardless of what error(s) it may have encountered. You should only use a forceful reboot if you cannot reboot gracefully, as it may case data loss.

FormMail Clone: A piece of software that imitates the function of FormMail. FormMail is used to create an email message from data that a user enters into the text fields on a web page, and send the message to the intended recipient.

Forwarder: A tool that lets you forward a copy of every email message 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 without first creating the original address, messages will be forwarded to the end address without being sent to the original address, as 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, including a final dot is not necessary, but the domain name must contain at least 2 dots. FQDNs must be written in lowercase letters.

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

FTP (File Transfer Protocol): A method of transferring files from one computer to another. cPanel & WHM 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®).

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

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. 3 generators can be configured through WHM: Analog, AWStats, and the Webalizer.

GnuPG (GNU Privacy Guard): A suite of tools used for data encryption and signing. These tools are most commonly used for signing emails. For more information, see the GnuPG website.

Graceful Reboot: The preferred way to restart your server. This method stores new system information before shutting down.

gzip: A program which compresses files for disk space conservation, minimizing transfer times, and making 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 used by websites managed by the account. Files 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.

Hostname: 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 using WHM’s Hostname feature. Please note that the server hostname is distinct from your domain name.

HotLink: 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 is using your bandwidth to serve those files.

.htaccess: A file that resides in a specific directory, and contains configuration information applying 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.

.htpasswd: A file that resides in a specific directory, along with an .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) for transferring data over the Internet.

httpd.conf: The configuration file for the Apache web server. More information about httpd.conf can be found at

ICQ: An instant messaging service. You may choose to receive updates from your server via ICQ. More information about ICQ can be found at

IMAP (Internet Message Access Protocol): Along with POP3, 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 into multiple computers to check email, IMAP will allow the user to see what 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 reading 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.html, index.htm or index.php, 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.

Interchange: A full-featured e-commerce application server that will allow you to conduct business online, granting your users a virtual shopping cart, payment method, and more.

IonCube: A loader that, if enabled, cPanel can use for loading PHP. More information about IonCube can be found at

IP (Internet Protocol) Address: A number that identifies a computer on a network, making 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 (also Jailshell): A CLI configuration that restricts users’ access rights by partitioning the system into smaller parts. This will prevent a user from leaving his or her user directory, restricting access to the file system and some commands.

Java: A computer programming language 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.

Kernel: 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.

Key: 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 filename extension .key.

Leech: A visitor who uses another person’s password to access a restricted area of a website. cPanel allows you to prevent leeching by redirecting likely offenders or disabling accounts whose passwords have been compromised.

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

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

Local Host: An easy way to refer to the computer that you are currently working on.

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

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

Logaholic: A web analytics program that delivers information about your website’s traffic, keywords, and content. More information about Logaholic can be found at

Log Files (see also the definition of Log, above):

access_log — A file containing a record of 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 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 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 encountered by tailwatchd, the daemon that monitors your server’s logs. This can be found at /usr/local/cpanel/logs/tailwatchd_log.

Maildir: A format for storing email wherein individual messages are stored with unique filenames. Maildir is rapidly becoming the standard mail storage format. We recommend using Maildir. See also mbox.

Mailing List: A list of email addresses which 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 uses a program called Mailman for mailing list software. More information can be found at the Mailman website,

Mailman: Mailing list software that sends email messages to a group of specified email addresses. More information about Mailman can be found at

Mail Transfer Agent: A program responsible for sending and receiving email messages. Also known as a message transfer agent.

mbox: A format for storing email wherein messages are kept in a single file. This method is outdated and is not recommended. See also Maildir.

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 lets you specify which application should be used to open files with a given extension.

Modulus: In encryption algorithms such as 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 using the SSL Key/Crt Manager feature.

mod_userdir: A feature of Apache that lets visitors view websites on your server by typing your hostname followed by a tilde and the website owner’s username. (Example: Disabling this via the WHM Security Center is desirable, as the bandwidth used when the site is accessed using this method is attributed to the web host’s main domain, skipping bandwidth monitoring systems. More information about mod_userdir can be found at

Mount: In general computing, this is the act of making the file system 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. More information can be found on 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 using an email scanning service or custom mail delivery, the server administrator may need to change the MX record for a domain using the Edit MX Entry feature in WHM.

MySQL: 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. WHM lets server administrators manage MySQL database services via the SQL Services section.

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

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

NFS (Network File System): Allows users to access remote files as though the hardware they are accessing to manipulate the file was attached directly to the local machine. This daemon is disabled by the WHM Quick Security Scan feature.

nfs statd: A process used for NFS file system mounting. This daemon is disabled by the WHM Quick Security Scan feature.

nis (Network Information Service): A directory protocol for distributing information across or within networks. This daemon is disabled by the WHM Quick Security Scan feature.

Nobody: 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.

nsd: DNS server daemon. More information about nsd can be found at

open_basedir: A feature that uses PHP to prevent users from opening files outside their home directories. This can be enabled using WHM’s PHP open_basedir Tweak feature.

Open Relay: A mail server configuration that allows anyone to send mail through the server. For security reasons, allowing your server to operate as an open relay is strongly discouraged.

Option Module (“opt mod”): An Apache configuration option that advanced administrators can add to the EasyApache (Apache Update) interface.


• A set of resource limits assigned to a user’s account. You can create, edit, and delete packages using the WHM Packages feature.

• Pieces of software that are bundled together for archiving and installation. cPanel packages, such as FTP and MySQL software, can be updated using the Update Config feature.

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, as is a parked domain for

PASV (Passive Mode): A mode for FTP connections that will initiate connections from the client side. Using this mode may be helpful if a user is having problems connecting 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 consisting of PHP programs which can perform useful functions for your website.

PECL (PHP Extension Community Library): A repository for C extensions (pieces of software) designed for use in PHP. More information can be found on the PECL website.

Perl: Known for its ability to process text, Perl is a useful language for web applications. Perl applications are commonly found as .pl, .pm, and .cgi files and may require Perl modules. Perl modules can be installed from cPanel (using the Perl Modules screen) and in WHM (using the Install a Perl Module screen).

Perl Module: A piece of software written in the Perl language. Modules are common pieces of software that are reused often. For example, rather than writing a set of functions to display calendars, a user can simply use a calendar module.

PHP: 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 cPanel through the PHP PEAR Packages feature and in WHM through the Module Installers feature.

phpMyAdmin: A graphical application that allows server administrators to manipulate and manage MySQL databases over the Internet. Full documentation for phpMyAdmin can be found at its creators’ website:

PHP Package: A piece of software written in the PHP language.

PHPsuExec: Like suEXEC for CGI, PHPsuExec allows users to execute PHP code under their own user ID. By default, PHP is executed using 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 via POP3 or IMAP to send mail for 30 minutes without reauthenticating through SMTP.

POP3 (Post Office Protocol version 3): Along with IMAP, one of the two most widely used email transfer methods. POP3 simply copies every message in an email account to a local computer, removing 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.

Portmap: 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 the Quick Security Scan feature.

POSIX (Portable Operating System Interface): A standardized collection of commands for the Unix operating system.

PostgreSQL: A database management system, much like MySQL. More information can be found on the PostgreSQL website.

Private Key: A string of characters that a computer uses to encode or decode encrypted messages it receives. Encryption schemes use a matching pair of keys (one public, one private) to create a secret code so that anyone looking at messages 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 is integral to protecting your confidential information and should be safeguarded appropriately.

Process: An instance of a program running on your machine.

ProFTPd: One of 2 FTP servers included in your installation of WHM. The other is Pure-FTPd. More information about ProFTPd can be found at

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

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

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

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

Public Key: A string of characters that a computer uses to encode or decode 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.

Pure-FTPd: One of 2 FTP servers included in your installation of WHM. The other is ProFTPd. More information about Pure-FTPd can be found at

Python: A programming language which is used for many applications. When you encounter this term under Update Config, it refers to the Python interpreter, which must be installed on your server before it can run Python programs. More information about Python can be found at

Quotas: Limits to the amount of disk space a user is allowed to take up. 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.

RBL (Realtime Blackhole List): A list of mail servers known to send spam. You are able to subscribe to the list and block incoming mail from such mail servers using the WHM Exim Configuration Editor.

Redirect: A feature that sends users to a different domain than the one they were trying to access. For example, a user may reach by typing cPanel allows website owners to set up either temporary or permanent redirects. See also domain forwarding.

Referer: A web page which 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 of formatting text so that a specified program can process it, using it to search in a prescribed way. A wildcard character such as an asterisk (*) is an example of a regular expression.

Relayer: A user who forwards email to a secondary destination. WHM’s View Relayers feature lets you 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. Please visit our documentation on cPanel versions and the release process for an in-depth discussion of Release Tiers.

Reseller: 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.

Resolver: The client side of the DNS system. Resolvers are programs that process DNS queries, working 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.

Rollback: In computing, a rollback involves restoring any part of a system to a previous configuration.

Root: 1) Specific to Unix and Unix-based systems, the system account. This account is used by a system administrator and carries full privileges for configuring 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 wording for your cPanel interface when a needed term in the interface is missing from the primary language files. The root language file is located in the directory /usr/local/cpanel/lang. 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.

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

RSA: An algorithm for generating public and private keys when sending 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.

RubyGems: A package manager and program library for the Ruby programming language. Also see Gem. More information about RubyGems can be found at

SCP (Secure Copy Protocol): A method of transferring encrypted files from one computer to another. This method prevents data from being intercepted and read.

Script Hooks: A program that is triggered by some event. WHM allows you to embed custom hook scripts into the Apache configuration process using the EasyApache (Apache Update) feature.

Server Contact: The server administrator whose contact information is entered into the Basic cPanel & WHM Setup screen in WHM.

/server-info and /server-status: These pages contain general information about the server. You can use the Tweak Settings screen to configure which users are allowed to view this information.

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

Shell: 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, in effect, crashing the server. WHM offers a protective service from shell fork bombs.

Shopping Cart: A piece of software used on web servers during e-commerce. A shopping cart allows the shopper to hold items they wish to purchase while they are still shopping on the website.

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

Skeleton Directory: A directory that defines what 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.

SMTP (Simple Mail Transfer Protocol): This protocol is the standard for transmitting email messages across the Internet. It is namely used for sending mail to a mail server’s relayer.

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

SourceGuardian/OldSource Guardian: PHP loaders that utilize a binary bytecode and, sometimes, multiple levels of encryption. For more information visit You can use the Tweak Settings screen to select a PHP loader.

Spam: Chiefly, unsolicited email sent in bulk, usually by an automated system. As 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 received. Server administrators can use the Tweak Settings screen to enable these services for their users.

SpamAssassin: An application which can filter suspected spam. SpamAssassin can be configured to filter spam more or less aggressively, according to the user’s needs. Learn more about SpamAssassin at Server administrators can use the Tweak Settings screen 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. Enabling SPF can prevent your server from receiving 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.

Spoof: An attack wherein the attacker conceals his identity by appearing as another user through the falsification of data, such as email headers. Enabling SPF makes it more difficult for spammers to spoof a domain.

Sprite: 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, clicking Generate Sprites in the Branding Editor can cause the sprite file to upload properly.

SQL Database: A type of relational database management system. WHM is compatible with both MySQL and PostgreSQL.

SquirrelMail Webmail: A webmail client that allows a user to check his or her email through an Internet browser.

SSH (Secure Shell Handler): A network protocol that allows a user to log into a remote machine securely. cPanel & WHM can create keys for authenticating a user’s identity during SSH login, and lets users manage SSH keys.

SSL (Secure Sockets Layer)/TLS (Transport Layer Security): TLS is simply the 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 (via the Install a SSL Certificate and Setup the Domain feature) to allow the site to be protected by SSL/TLS.

SSL Certificate: An electronic document (using the filename extension .crt) which binds a public key to an identity consisting of an email address, company, and location. This electronic document is a key piece in an authentication process.

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

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

Subdomain: 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

suEXEC: 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 using the system account known as nobody with the UID of 99.

Tar: 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.

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

Telnet: A network protocol that allows a user to log into 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.

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

Thumbnail: A version of an image file that is reduced in size, allowing for easy viewing of multiple images. cPanel includes a Thumbnailer tool as part of its Image Manager section.

Thumbnailer: 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 meant to represent the parent directory containing 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.

Tooltip: 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 within the tooltip information box.

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

Trust Key Relationship: A cryptographic scheme involving a public and private key pair.

UDP (User Diagram 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 for broadcasting messages over a network.

UID (User ID): The unique user number that any user on your server will be assigned during a session. Some important UIDs:

• 99 — nobody — Default executor of CGI scripts if suEXEC is disabled.

• 0 — root — The top-level system user.

Note: UIDs 0 through 100 are reserved for system accounts such as admin and root.

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

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

URI (Universal 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.

URL (Universal Resource Locator): On the web, a URL is a string of characters that identifies the location of a website. Since 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.

User: A person who uses a computer to accomplish some purpose.

VirtualHost: A method of hosting multiple domains on a single server and sometimes on a single IP address. To learn about the types of virtual hosting, visit

Visitor: A person who views your website.

Webalizer, The: A program that displays various statistics for a website using tables and graphs. Full documentation for The Webalizer can be found at its creators’ website:

Web Browser: An application 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.

Webmail: Any application which 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 connected to the Internet without having to install or configure a specific mail program.

Web Root: The top-most directory of your website (namely, 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.

Wheel Group: This group of users is allowed to execute the su or 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, designed for web hosts, resellers, and system administrators.

WHOIS: A Unix/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.

www: 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 added to email messages sent from a PHP script on your server, detailing the script’s location. Enabling these headers can help you locate insecure email scripts being abused by spammers. You can enable these headers using the Tweak Settings feature.

XSRF Attack (Also, CSRF): XSRF and CSRF stand for Cross-Site Request Forgery. This attack exploits a trusted website by forcing a user to execute unauthorized commands, usually through a hyperlink. To help prevent XSRF attacks, you can use Tweak Settings to limit the functions that cPanel and WHM perform by requiring that each request come from a domain or IP on your server.

Zone: A DNS Zone, an administrative space or portion of the Domain Name System. This space is responsible for directing 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.