An instant messaging service that you can use to receive updates from your server. You can configure these notifications in cPanel’s Contact Manager interface (WHM » Home » Server Contacts » Contact Manager).
A third-party authority (for example, OpenID Connect) that offers external authentication to log in to other sites or services.
Third-party developers can use External Authentication modules to authenticate with OpenID Connect-compliant identity providers.
You can configure External Authentication in WHM’s Manage External Authentications interface (WHM » Home » Security Center » Manage External Authentications)
Index Page
The default page, generally index.html, index.htm, or index.php, that visitors view when they access a website directory. If no index page exists for the specified directory, the visitor sees a list of files in that directory, unless you disable indexing in cPanel’s Indexes interface (cPanel » Home » Advanced » Indexes).
Internet Message Access Protocol (IMAP)
One of the two most widely-used email transfer methods along with POP3. 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 allows the user to see which messages they have viewed, replied to, or forwarded.
More:
For more information, read our IMAP vs. POP3 documentation.
Internet Protocol (IP)
The main protocol that relays information across the internet. This protocol uses IP addresses to deliver information from one host to another. cPanel & WHM supports two versions of Internet Protocol:
IPv4 is an older version that uses 32-bit IP addresses. This version has limited availability, but is the more popular and accessible.
IPv6 is a newer version that uses 128-bit IP addresses. This version has vast availability of addresses, but requires an IPv6-enabled network and server.
Warning:Due to networking requirements, you cannot run an IPv6-only cPanel & WHM server. You must have at least one IPv4 address.
Internet Protocol (IP) Address
A number that identifies a computer on a network, which makes it possible for other computers to find and communicate with it. You can add new IP addresses to your IP address pool in WHM’s Add a New IP Address interface (WHM » Home » IP Functions » Add a New IP Address).
Internet Relay Chat (IRC)
An application layer protocol of real-time online communication that allows both group discussion and one-to-one messaging, as well as data transfer. Third-party developers can create custom modules to send notifications to IRC and other services.
IonCube®
A loader that, when enabled, can load PHP for cPanel & WHM.
A CLI configuration that restricts users’ access rights. The system limits shell sessions to a filesystem that does not contain the home directories of other cPanel users on the system.
cPanel & WHM uses VirtFS to provide jailshell access.
A computer programming language that many web applications use. These small applications, which run within the context of a browser, are called applets.
A file format that uses human-readable text to store and exchange data. JSON contains data objects in attribute-value pairs and array data types.
cPanel & WHM uses JSON for API output and some internal data storage.
You can use several basic variables to filter or sort API output in JSON.
K
Kernel
The central component of a 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, keys encrypt or decrypt information.
Keys are an important part of encryption and security, and you should guard them appropriately.
Using cPanel & WHM usually includes working with, for example, SSH keys, DNSSEC keys, and various types of cPanel & WHM-specific access keys.
Known Netblock
A class C address space that contains an address from which a user has successfully logged in. You can configure settings for known netblocks in WHM’s Greylisting interface (WHM » Home » Email » Greylisting).
L
LAMP
An acronym for the combination of Linux, Apache, MySQL, and PHP. This is a common combination of software for web servers.
A visitor who uses another person’s password to access a restricted area of a website. cPanel & WHM lets you redirect likely offenders or disable accounts with compromised passwords in order to prevent leeches. To do this, use cPanel’s Leech Protection interface (cPanel » Home » Security » Leech Protection).
Legacy
A term for an old software program or computer system that is still in use, or for a previous version of a cPanel & WHM feature.
Linked Node
A node that a server administrator designates to either assign tasks to or receive tasks from another node. For example, a parent node may assign all mail tasks for a cPanel account to a child node.
The part of a system that loads a program. Use WHM’s Tweak Settings interface (WHM » Home » Server Configuration » Tweak Settings) to select the loader that cPanel & WHM uses for PHP.
Local Host
The computer that you currently work on.
Local User
A user who accesses a service on the machine on which the service exists, as opposed to remotely.
Log
A file that the server automatically creates, which records activities that specific programs and applications on the server perform. For example, error logs list the errors that visitors have encountered on websites that Apache generates.
Log Files
Files that contain status messages, warnings, and other real-time information about your server and its processes. cPanel & WHM includes many log files.
Long-Term Support (LTS)
One of cPanel & WHM’s release tiers. WebPros International, LLC supports this version for a period of one year before designating the next LTS version.
A record that specifies where the system sends email for a domain, because 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 Email Routing Configuration interface (WHM » Home » DNS Functions » Email Routing Configuration).
cPanel users can configure MX records in cPanel’s Email Routing interface (cPanel » Home » Email » Email Routing).
Mail Server Name Indication (Mail SNI)
Allows clients to request a specific hostname at the beginning of the handshake process. In our documentation, SNI refers to this protocol in relation to Apache, while Mail SNI refers to this protocol in relation to Exim.
More:
For more information, read our Guide to SSL documentation.
Mail Transfer Agent (MTA)
A program that sends and receives email messages. Exim is an MTA.
maildir
A format that stores email as individual messages with unique filenames in flat files. You can manage maildir with WHM’s Mailbox Conversion interface (WHM » Home » Email » Mailbox Conversion).
Mailing List
A list of email addresses that mailing list members can use to communicate. Alternatively, you can use a mailing list to send email messages to a large group of people.
cPanel & WHM uses the Mailman program for mailing list software.
You can use cPanel’s Mailing Lists interface (cPanel » Home » Email » Mailing Lists) to create and manage mailing lists.
Mailman
Mailing list software that sends email messages to a group of specified email addresses.
A WebPros International, LLC website that lets you perform license-related tasks. Hosting providers log in to Manage2 to add, update, or remove cPanel product licenses, or to manage and pay invoices from WebPros International, LLC.
MariaDB®
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 & WHM provides an integrated MariaDB installation and database editing tools.
You can upgrade the server’s MariaDB version in WHM’s Upgrade Database Version interface (WHM » Home » Database Services » Upgrade Database Version).
mod_userdir
An Apache module that allows visitors to enter your hostname, a tilde (~), and the website owner’s username in order to view a website (for example, http://host.example.com/~username).
Important:
We recommend that you disable the mod_userdir module in WHM’s Apache mod_userdir Tweak interface (WHM » Home » Security Center » Apache mod_userdir Tweak) because the system accounts for bandwidth per-host rather than per-user.
Modulus
In encryption algorithms like RSA), the modulus is the number that both the private and public keys have in common. You can view a key’s modulus in WHM’s SSL Storage Manager interface (WHM » Home » SSL/TLS » SSL Storage Manager).
Mount
In general computing, to mount a file system is to make it accessible to users. In a Unix or Linux operating system, you can use the mount 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.
A component of a file that identifies the file type, so that browsers handle it correctly.
cPanel & WHM lets you specify which application to use to open files with a specific extension.
You can add and manage MIME types in cPanel’s MIME Types interface (cPanel » Home » Advanced » MIME Types).
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 & WHM provides an integrated MySQL installation and database editing tools.
You can upgrade the server’s MySQL version in WHM’s Upgrade Database Version interface (WHM » Home » Database Services » Upgrade Database Version).
N
Nameserver
A physical computer that contains a list of domain names and their IP addresses. These computers 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 may require 48 hours or more to reach all of the nameservers on the internet (propagate). Several types of nameserver exist.
Local — Local nameservers are authoritative nameservers. They reside on the same server that hosts the nameserver’s cPanel accounts.
Clustered — Clustered nameservers exist in a collection of nameservers that all share information and authoritative nameserver status. These nameservers prevent down time. If one server fails, additional servers are available to perform the necessary functions.
Private or Custom — This type of nameserver is a custom-branded or vanity alternative name for the authoritative nameserver.
Remote — Remote nameservers are authoritative nameservers that a separate server hosts.
The remapping of one IP address space to another by modifying the network address information of packets’ IP headers while in transit across a router. This method allows for the use of a single IP address on an entire private network. For more information about NAT, read our 1:1 NAT documentation.
Important:
For cPanel & WHM services to function correctly, you or your network administrator must enable loopback (or hairpin) NAT on both the server and its firewall. Loopback NAT allows the server to access a public IP address internally from its corresponding private IP address.
Network File System (NFS)
Allows users to access remote files as though the accessed storage was part of the local machine.
A Unix or Linux system account with the UID of 99. This system account executes CGI and PHP scripts if suEXEC is disabled.
O
Onboarding Assistant
The Onboarding Assistant appears for new or migrated cPanel user accounts to welcome the user and offer a starting point to begin using the cPanel interface. The interface’s options will change depending on your hosting provider and account settings.
Open Relay
A mail server configuration that allows anyone to send mail through the server. You can enable or disable this configuration in the Mail section of WHM’s Tweak Settings interface (WHM » Home » Server Configuration » Tweak Settings).
Warning:
For security reasons, we strongly recommend that you don’t allow your server to operate as an open relay.
open_basedir
A feature that uses PHP to deny users the ability to open files that are outside of their home directories. You can modify this feature in the Editor Mode section of WHM’s MultiPHP INI Editor interface (WHM » Home » Software » MultiPHP INI Editor).
OpenID® Connect (OIDC)
A standard for third-party authentication. cPanel & WHM’s External Authentication feature uses OpenID Connect to communicate with third-party authentication providers.
Third-party developers can use External Authentication modules to authenticate with OpenID Connect-compliant identity providers.
You can configure External Authentication in WHM’s Manage External Authentications interface (WHM » Home » Security Center » Manage External Authentication).
The background software that runs all of the other software applications on your system. The OS is a required part of any server or computer. cPanel & WHM supports specific versions of the AlmaLinux OS, Rocky Linux, CloudLinux, and Ubuntu operating systems.
An Apache configuration option that adds features to the EasyApache system.
Organizational Validation (OV) Certificate
A digital certificate used for SSL/TLS verification. The certificate authority (CA) verifies that the applicant controls the DNS domain through a vetting process. These certificates enable HTTPS on a user’s web browser address bar and state that the site is secure with a Secure Site Seal.
These certificates are more secure than a DV certificate.
You can purchase and install certificates in cPanel’s SSL/TLS Wizard interface (cPanel » Home » Security » SSL/TLS Wizard).
P
Package
A package may refer to:
The set of resource limits that hosting providers assign to a user’s account. System administrators can create, edit, and delete packages in WHM’s Packages section.
A collection of software that publishers bundle together for distribution and installation. WebPros International, LLC provides various third-party software, such as FTP and MySQL, as packages that the rpm.versions system manages.
A second domain that points to a primary domain. For example, both http://www.cpanel.net/ and http://www.cpanel.com/ point to the same website, because cpanel.com is a parked domain for cpanel.net.
This makes your website available from another domain name.
In cPanel, we refer to parked domains as aliases.
Passive Mode (PASV)
A mode for FTP connections that initiate connections from the client side. You can use this mode if a user has problems when they attempt to connect to an FTP server through a firewall.
A service that reports the visitor’s operating system and other information for email notifications. This information will help you quickly identify visitors who trigger events that cause alerts.
A component of software in the Perl programming language that developers commonly reuse. For example, a developer can use a calendar module in a program so that they don’t need to write a new set of functions to display calendars. You can install Perl modules in either of the following interfaces:
WHM’s Install a Perl Module interface (WHM » Home » Software » Install a Perl Module)
Phishing
A type of attack in which the sender pretends to be a known entity to try to get an email recipient to give out sensitive information. Spammers often use phishing to try to get usernames, passwords, or credit card details.
PHP
A computer scripting language that many web-based applications use. Some PHP applications require PEAR packages.
More:
For more information, read our About PHP documentation.
PHP Extension and Application Repository (PEAR)
A repository of PHP code. cPanel lets you search for and install PEAR packages that consist of PHP programs and which perform useful functions for your website.
Note:
You can install PEAR packages in either of the following interfaces:
An alternative PHP FastCGI implementation that improves performance of PHP scripts on servers.
More:
For more information, read our PHP-FPM documentation.
phpMyAdmin
A graphical application that allows server administrators to manipulate and manage MySQL databases over the internet. Server administrators can access this feature in WHM’s Database Services section.
For more information about WHM plugins, read our Guide to WHM Plugins documentation.
Plus Addressing
Plus addressing (or subaddressing) adds a plus character and string after an email account username. For example, the john@example.com email address could use the john+list@example.com plus address. The email account would recognize these messages and place them in the list mailbox. If the mailbox does not exist, the account sorts this message to the inbox mailbox.
More:
For more information, read our Email Accounts documentation.
POP Before SMTP
An authentication method for mail servers. This method allows a user who received mail through POP3 or IMAP to send mail for 30 minutes without the need to re-authenticate through SMTP. WHM users can enable or disable this via WHM’s Tweak Settings interface (WHM » Home » Server Configuration » Tweak Settings).
More:
For more information, read our IMAP vs. POP3 documentation.
A widely-used email transfer method, like IMAP. POP3 copies every message in an email account to a local computer and then deletes these messages from the mail server. The system does not send information back to the email account about message replies or forwarding.
More:
For more information, read our IMAP vs. POP3 documentation.
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 key and one private key) to create a secret code.
When you use an encryption scheme, anyone who looks at messages that your computer sent or received cannot determine the contents of those messages without access to the private key. A private key protects your confidential information, and you should store it safely.
Process ID (PID)
A unique number that your server assigns to each process that runs. You can view a list of running processes with PIDs in WHM’s Show Current Running Processes interface (WHM » Home » System Health » Show Current Running Processes).
ProFTPD
One of cPanel & WHM’s included FTP servers. You can select an FTP server in WHM’s FTP Server Selection interface (WHM » Home » Service Configuration » FTP Server Selection).
A string of characters that a computer uses to encode or decode the encrypted messages it receives. Typically, you place a public key on a server so that you can establish an encrypted connection to that server.
public_ftp
A subdirectory, 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 access when they connect to your site through anonymous FTP.
public_html
A subdirectory inside a user’s home directory. It contains files that are publicly-accessible through the HTTP protocol.
The www directory is a link to the public_html directory.
Visitors can view any files and folders in the public_html directory over the internet, unless the website owner specifically protects them with password protection or the .htaccess file.
Pure-FTPd
One of cPanel & WHM’s included FTP servers. You can select an FTP server in WHM’s FTP Server Selection interface (WHM » Home » Service Configuration » FTP Server Selection).
A popular programming language. You can install the Python interpreter, which allows your system to run Python programs, in WHM’s Update Preferences interface (WHM » Home » Server Configuration » Update Preferences).
Q
Quotas
Limits to the amount of system resources, like bandwidth or disk space, that a user may use.
To set up quotas, use WHM’s Initial Quota Setup interface (WHM » Home » Server Configuration » Initial Quota Setup).
To modify a user’s disk space quota, use WHM’s Quota Modification interface (WHM » Home » Account Functions » Quota Modification).
R
Raw Opts (Custom Configuration Flags)
Lines of data that advanced users can add to a specific file on the server in order to customize Apache’s configuration.
More:
For more information, read our EasyApache documentation.
Realtime Blackhole List (RBL)
A list of mail servers that send spam. You can subscribe to the RBL, blocking incoming mail from those mail servers, in WHM’s Exim Configuration Manager interface (WHM » Home » Service Configuration » Exim Configuration Manager).
Red Hat® Enterprise Linux® (RHEL)
A commercial Linux operating system distribution. We support the following RHEL-derived operating systems:
A feature that sends users to a different domain than the one that they attempted to access. For example, a user may reach example.com when they type example2.com.
Website owners to set up either temporary or permanent redirects.
Users can manage their redirects with cPanel’s Redirects interface (cPanel » Home » Domains » Redirects).
Referer (HTTP Referer)
A web page that links to a site. This spelling is the industry standard term, though it is a misspelling of the word in other uses.
Regular Expressions
Often seen as regex or regexp. Regular expressions allow you to 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.
Relayer
A user who forwards email to a secondary destination. WHM’s View Relayers interface (WHM » Home » Email » View Relayers) lets you view users on your server who have relayed mail.
RELEASE
One of cPanel & WHM’s release tiers. Versions on this tier are feature-complete and well-tested.
A repository is a collection of packages on your local machine or one that you can access remotely. You can use several repositories at the same time.
Reseller
In the hosting industry, resellers use server resources (bandwidth and disk space) and sell those resources in smaller packages to individual cPanel & WHM users.
You can create reseller accounts in WHM’s Create a New Account interface (WHM » Home » Account Functions » Create a New Account).
You can manage resellers and their accounts in WHM’s Reseller Center interface (WHM » Home » Resellers » Reseller Center).
Resolver
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 /etc/resolv.conf file usually points to a server’s resolvers.
You can update resolvers in WHM’s Resolver Configuration interface (WHM » Home » Networking Setup » Resolver Configuration).
Restoration
In web hosting, a process that uses backup files to replicate an account on a server.
This functionality is useful, for example, to recover damaged files or data or in the case of a full hardware failure.
You can manage account restoration in WHM’s Transfer or Restore a cPanel Account interface (WHM » Home » Transfers » Transfer or Restore a cPanel Account).
A feature in WHM that performs additional security checks on backup files, and then restores them to the server. You can manage account restoration in WHM’s Transfer or Restore a cPanel Account interface (WHM » Home » Transfers » Transfer or Restore a cPanel Account).
Reverse DNS lookup (rDNS)
A process that uses pointer records (PTR) to convert IP addresses (for example, 192.0.2.0) to domain names (for example, www.example.com).
In computing, a rollback involves the restoration of any part of a system to a previous configuration.
Root
This may refer to:
Specific to Unix and Unix-based systems, the system account. The system administrator uses this account, and it carries full privileges to configure a computer system. See UID.
The highest-level directory in a Unix or Unix-based system. Generally, we notate this directory with a forward slash (/).
Roundcube Webmail
A webmail client that allows users to check email through an browser rather than a mail client.
An algorithm that generates public and private keys 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.
Ruby
An object-oriented programming language.
More:
For more information about how to create web applications using Ruby in cPanel & WHM, read our How to Create Ruby Web Applications documentation.
RubyGems
Warning:
In cPanel & WHM version 66, we deprecated the legacy Ruby codebase and plan to remove it in a future release. This legacy Ruby codebase includes RubyGems applications.
A package manager for the Ruby programming language. Developers can use RubyGems as a self-contained format for Ruby programs and libraries. You can install and manage RubyGems in cPanel’s RubyGems interface (cPanel » Software » RubyGems).
Ruby on Rails® (RoR)
Warning:
In cPanel & WHM version 66, we deprecated the legacy Ruby codebase and plan to remove it in a future release. This legacy Ruby codebase includes Ruby on Rails applications.
An open-source framework that runs on the Ruby programming language.
More:
For more information, read our Ruby on Rails documentation.