(reference-glossary)= # Glossary We are currently compiling and defining terms for this glossary. If you would like to help, please visit our {ref}`contributions page ` for details on how to get involved. **Jump to:** {ref}`A ` -- {ref}`B ` -- {ref}`C ` -- {ref}`D ` -- {ref}`E ` -- {ref}`F ` -- {ref}`G ` -- {ref}`H ` -- {ref}`I ` -- {ref}`J ` -- {ref}`K ` -- {ref}`L ` -- {ref}`M ` -- {ref}`N ` -- {ref}`O ` -- {ref}`P ` -- {ref}`Q ` -- {ref}`R ` -- {ref}`S ` -- {ref}`T ` -- {ref}`U ` -- {ref}`V ` -- {ref}`W ` -- {ref}`X ` -- {ref}`Y ` -- {ref}`Z ` (terms_A)= ## A :::{glossary} ABI Application Binary Interface An ABI is an interface that defines how two modules interact with each other at the machine code level. Most often, these modules are applications using external libraries. An ABI defines a low-level and hardware-dependent interface compared to an {term}`API`, which is considered high-level and hardware-independent. ACL Access Control List An ACL is a list of access permissions that defines entities and their access rights to resources. ACLs can specify access with varying levels of granularity, ranging from full access to a resource, to permission for a specific operation. See also: * [the ACL manual page](https://manpages.ubuntu.com/manpages/noble/man5/acl.5.html) Related topic(s): * Security, {term}`OpenLDAP`, and {term}`Kerberos` AD Active Directory *Work in Progress* ADSys ADSys is an Ubuntu-specific Active Directory client developed by Canonical. ADSys complements System Security Services Daemon (SSSD) by adding native Group Policy Object support, privilege management, and custom scripts execution. See also: * [the ADSys documentation](https://documentation.ubuntu.com/adsys/en/stable/) Related topic(s): * {term}`Group Policy Object` and {term}`SSSD` AES Advanced Encryption Standard An AES is a symmetric encryption algorithm designed to encrypt data securely into an unreadable format that can only be decrypted with the same key used for encryption. Related topic(s): * Security Alertmanager Alertmanager is an open-source monitoring system developed by the Prometheus project to monitor and handle alerts. It offers several key features, including *Grouping* to combine alerts, *Inhibition* to suppress certain alerts when others are already firing, and *Silencing* to temporarily mute specific alerts. See also: * [the Alertmanager documentation](https://prometheus.io/docs/alerting/latest/alertmanager/) Related topic(s): * Observability and {term}`Prometheus` ALUA Asymmetric Logical Unit Access It is a storage concept used in Small Computer System Interface (SCSI) environments, particularly in Multi-Path Input/Output (MPIO) setups for shared storage systems like Storage Area Networks (SANs). ALUA informs a system about which paths to a storage device are optimal and which are non-optimal, enabling it to make smarter decisions about accessing shared disks. Related topic(s): * {term}`MPIO` {term}`SCSI`, {term}`SAN` AMD Advanced Micro Devices AMD can refer to: * The (AMD) company: semiconductor company that designs computer components * An AMD processor: a microprocessor designed and produced by the AMD company * All Intel/AMD 64-bit processors: the term "amd64" is commonly used to refer to 64-bit processors due to the company's role in developing this architecture. Related topic(s): * Networking Ansible Ansible is an open-source IT automation tool developed by Red Hat. It offers several automation features, enabling developers and organizations to automate provisioning, configuration management, and application deployment. See also: * [The Ansible website](https://docs.ansible.com/) Related topic(s): * Automation Apache2 A robust, open-source HTTP server software designed for the deployment and delivery of web-based applications and content. Functioning as a request-response service, Apache 2 processes HTTP requests from client applications, facilitating the transmission of static and dynamic web resources. It has a modular architecture, supporting a wide array of extensions, enabling customizable functionality including security protocols (e.g., {term}`SSL`/{term}`TLS`), server-side scripting, and content management. Widely deployed in server environments, Apache 2 is a foundational component of numerous web infrastructure stacks, underpinning a substantial portion of internet-accessible services. See also: * [The Apache project documentation](https://httpd.apache.org/docs/2.4/) Related topic(s): * Web servers API Application Programming Interface An API is a type of software interface that acts as a connection between different software programs, allowing them to communicate and exchange data. APIs exist on multiple layers of abstraction, from low-level APIs closest to system hardware to high-level web APIs that enable clients and remote servers to communicate. AppArmor AppArmor is a Linux security module that provides {term}`Mandatory Access Control (MAC) ` for programs. AppArmor restricts what applications can do, even when they are compromised. It enforces a set of security policies (called profiles) that define what files, capabilities, and system resources a given program is allowed to access. See also: * [The AppArmor website](https://apparmor.net/) Related topic(s): * Security Apport Apport is a debugging tool and crash reporting system used in Ubuntu and Debian-based Linux distributions. It can automatically detect crashes in programs and system services, collect detailed diagnostic data, generate crash reports, and prompt the user to send the report to developers via systems like Launchpad. It is typically disabled by default on production systems because it can expose sensitive information in logs, but is used during development or testing. See also: * [The Apport Wiki Page](https://wiki.ubuntu.com/Apport) Related topic(s): * Debugging APT Advanced Package Tool APT is a package management system used by Debian and Debian-based Linux distributions like Ubuntu. APT helps install, update, upgrade, and remove software packages from the command line. See also: * {ref}`package-management` armhf ARM hard-float armhf is a designation used in Linux distributions to describe a 32-bit variant of the ARM architecture that has hardware-based floating-point support. armhf is typically used for lightweight systems or backward compatibility, especially in embedded environments. Related topic(s): * arm32, arm64 ARP Address Resolution Protocol ARP is a network protocol used to map an IP address to a physical machine ({term}`MAC address`) on a local area network (LAN). Related topic(s): * Networking async asynchronous A term commonly used in programming to describe operations that take place without blocking the main execution thread. Instead of waiting for a particular operation to finish (such as reading a file or making a network request), "async" programs can keep running other operations in the meantime. These operations are often dispatched to the background, allowing them to run in parallel. If needed, however, the program can still wait for the result of an asynchronous operation. Related topic(s): * Concurrency, parallelism, and threading Authenticator An authenticator is any system, method, or mechanism used to verify a user's identity during the authentication process. It can range from something as simple as a password field (e.g., LDAP {term}`bind`) to more advanced tools like biometric scanners or one-time code generators. Authenticators are essential components of authentication protocols and can be used in both single-factor and multi-factor authentication setups. Related topic(s): * OpenLDAP, authentication autocommit autocommit is a database feature that automatically commits every individual SQL statement as soon as it is executed. When autocommit is enabled, every SQL statement is treated as its own transaction and is applied immediately and permanently. This means it is impossible to undo or roll back a statement executed with autocommit enabled. While autocommit is a common default in many systems, behavior can vary depending on the database or language bindings. For example, in Python's `sqlite3` module, Python 3.12 introduces changes to transaction control, allowing explicit control over autocommit mode. See also: * [autocommit behavior in Python's `sqlite3` module](https://docs.python.org/3/library/sqlite3.html#transaction-control) Related topic(s): * Databases autodetect autodetect is the ability of a system to automatically detect and configure hardware or settings without user input. In Ubuntu Server and other Linux systems, this is used during boot or installation to identify devices like disks, network interfaces, or keyboard layouts. The kernel, installers, and configuration tools rely on autodetection to simplify setup by loading the right drivers and defaults based on the system's hardware and environment. Related topic(s): * Kernel modules autoinstall Autoinstall is a feature in Ubuntu Desktop and Ubuntu Server that provides fully automated installations using a pre-defined configuration file. This file describes how the system should be installed, including disk partitioning, user accounts, package selection, and network settings. See also: * [The Autoinstall documentation](https://canonical-subiquity.readthedocs-hosted.com/en/latest/intro-to-autoinstall.html) Related topic(s): * cloud-init autorid autorid is a Samba ID mapping backend that automatically assigns {term}`UID` and {term}`GID` values to security identifiers (SIDs) when integrating with Active Directory (AD). It ensures consistent and persistent Unix ID mapping without requiring manual configuration for each domain or user/group. See also: * [The autorid Samba Wiki](https://wiki.samba.org/index.php/Idmap_config_autorid) Related topic(s): * Samba, Active Directory AWS Amazon Web Services AWS is a cloud computing platform that offers a wide range of on-demand services such as compute, storage, networking, machine learning, analytics and much more. It allows individuals and companies to run applications without owning physical hardware, to scale resources up or down as needed, and to pay only for what they use. See also: * [The AWS documentation](https://docs.aws.amazon.com/) Related topic(s): * Clouds ::: (terms_B)= ## B :::{glossary} backend *Work in Progress* Backports *Work in Progress* Backtrace *Work in Progress* BDC Backup Domain Controller *Work in Progress* bind *Work in Progress* BindDN *Work in Progress* BIOS *Work in Progress* BMC Baseboard Management Controller *Work in Progress* bootloader *Work in Progress* bootstrap *Work in Progress* btrfs B-tree File System *Work in Progress* ::: (terms_C)= ## C :::{glossary} CA Certificate Authority *Work in Progress* CAC Common Access Card *Work in Progress* CARP Cache Array Routing Protocol *Work in Progress* CCID Chip Card Interface Device *Work in Progress* CDB Command Descriptor Block *Work in Progress* CGNAT Carrier-Grade Network Address Translation *Work in Progress* CGI Common Gateway Interface *Work in Progress* checksums *Work in Progress* chrony *Work in Progress* chroot *Work in Progress* CIDR Classless Inter-Domain Routing *Work in Progress* CIFS Common Internet File System *Work in Progress* CIS Center for Internet Security *Work in Progress* CLVM Clustered Logical Volume Manager *Work in Progress* CMS Configuration Management System *Work in Progress* CN Common Name *Work in Progress* colocation *Work in Progress* conffile *Work in Progress* config *Work in Progress* connectionless *Work in Progress* containerization *Work in Progress* CPU Central Processing Unit *Work in Progress* CRL Certificate Revocation List *Work in Progress* crypto cryptographic *Work in Progress* CSR Certificate Signing Request *Work in Progress* CVE Common Vulnerabilities and Exposures *Work in Progress* ::: (terms_D)= ## D :::{glossary} DAC Discretionary access control A form of access control where the owner of a resource can grant/revoke permissions to other users. Related topic(s): * Security daemonize The process of converting a program to run in the background as a service, independent of user sessions. DARPA Defense Advanced Research Projects Agency A research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use in the military. DASD Direct Access Storage Device This term was coined by IBM to refer to a type of storage that allows random access to storage (hard-drives, optical discs, etc). It contrasts with sequential access storage such as magnetic tape or punched cards. Related topic(s): * Storage Datagram In networking, a self contained, independent packet sent over a network. It can be routed from source to destination without relying on earlier or subsequent transfers. Related topic(s): * Networking dblink Database link A connection between two databases (mainly Oracle and PostgreSQL), allowing one database to query data from the other. Related topic(s): * Databases DC Domain Component *Work in progress* DDNS Dynamic Domain Name System A service that automatically updates DNS records when the underlying IP address changes (aka, dynamic IP). Related topic(s): * Networking debconf A {term}`configuration management system ` handling the configuration of software packages during installation or upgrades by prompting users for necessary settings and storing them for subsequent installations or updates. deduplication Process of removing duplicate copies of data in storage spaces. The redundant data is then replaced with a reference to the original. denylist In cyber-security, a denylist is a list of entities (IP, domains, emails, etc), that are explicitly denied access to a system or service. Related topic(s): * Security DER Distinguished Encoding Rules A standardized encoding format for data (mostly cryptographic certificates and keys) for transmission and storage. DGC Distributed Garbage Collection A process used in distributed systems to manage memory across multiple interconnected computers allowing identification and reclaiming of unused memory across nodes. DHCP Dynamic Host Configuration Protocol A network protocol used to automatically assign network configuration details (IP, DNS, gateway, etc) to devices allowing for easy network management and connections within the network. DHCPD Dynamic Host Configuration Protocol Daemon Server software responsible for assigning the network configuration via DHCP. DIT Directory Information Tree In directory services (LDAP) this is a hierarchical tree-like structure used to organize and store information. Related topic(s): * OpenLDAP DKMS Dynamic Kernel Module Support A framework used in Linux systems to automatically rebuild and install kernel modules when the kernel is updated. Related topic(s): * Kernel DMA Direct Memory Access DMA is a technology that allows peripheral devices (hard drives, network cards, etc) to access the system's memory directly, bypassing the CPU and thus improving performance. DMAR Direct Memory Access Remapping DMAR is a technology used to control and secure {term}`Direct Memory Access ` operations and ensure that devices can only access memory regions they are authorized to. This helps to prevent unauthorized access, memory corruption, or security vulnerabilities. It is often used in virtualized environments to isolate devices between {term}`virtual machines (VMs) ` and the host system. dmesg A command in Linux systems that displays system logs related to hardware, drivers, and kernel events, such as system startup, device detection, and errors. It is commonly used for troubleshooting hardware issues and system diagnostics. DN Distinguished Name In directory services (LDAP), this is a unique identifier used to represent an entry in a directory, such as a user or a group. It's often composed of sub-components like {term}`CN`, {term}`OU`, or {term}`DC`. DNS Domain Name System A system that translates human-readable domain names (e.g. `ubuntu.com`) to their IP addresses (`185.125.190.20`). Related topic(s): * Networking dnsmasq A lightweight, open-source {term}`DNS` and {term}`DHCP` server software. DNSSEC Domain Name System Security Extensions DNSSEC is a set of security extensions to {term}`DNS` which allow DNS data to be verified for authenticity and integrity. Related topic(s): * Security Docker One of the most popular containerization platforms, which allows developers to package applications -- together with their dependencies -- into lightweight containers. This provides a consistently reproducible environment for deploying applications. Related topic(s): * Containers DocumentRoot A directive in web server configuration files that specifies the directory on the server where web files are stored (root location). dpkg dpkg is a package manager for Debian-based systems. It can install, remove, and build packages, but unlike other package management systems, it cannot automatically download and install packages -– or their dependencies. DRBD Distributed Replicated Block Device A software-based storage solution for Linux that allows for the mirroring of block devices between multiple hosts. The replication is transparent to other applications on the host systems. Any block device hard disks, partitions, RAID devices, logical volumes, etc can be mirrored. Related topic(s): * Storage DTLS Datagram Transport Layer Security A protocol that provides security for datagram-based communication, such as {term}`UDP`. It is designed to offer similar security features as {term}`TLS` but adapted for the connectionless nature of datagram protocols. ::: (terms_E)= ## E :::{glossary} EAL Environment Abstraction Layer A software layer that provides a standardized interface between an operating system and the underlying hardware. It abstracts hardware-specific details, allowing software to run on different hardware platforms without modification. ECKD Extended Count Key Data A disk storage format used by IBM mainframe systems, which provides advanced features such as better error detection and correction, as well as enhanced management of data records. EFI Extensible Firmware Interface A type of firmware interface designed to initialize hardware and load the operating system during the boot process of a computer. Replacement for the older {term}`BIOS` and ancestor of the {term}`UEFI`. ELinks A text-based web browser for Unix-like operating systems. It allows users to browse the web in a terminal, making it ideal for environments without a {term}`GUI`. Engenio A company that developed and manufactured storage systems including {term}`SAN` and {term}`NAS`. Later acquired by LSI Corporation and then by Seagate Technology. EOL End of life When a product, service, software is no longer supported or maintained. ERD Enterprise Ready Drivers Drivers that are specifically designed and optimized for use in enterprise environments, where stability, performance, and reliability are critical. ESM Expanded Security Maintenance A service provided by Canonical to extend security updates and patches for older {term}`LTS` releases of the Ubuntu operating system after the LTS standard support period has ended. ESXi A bare-metal virtualization platform created by VMWare that enables multiple virtual machines to operate on a single physical server. ::: (terms_F)= ## F :::{glossary} failover In a {term}`Storage Area Network (SAN) ` environment, this occurs when data flows into an alternative I/O path because a cable, switch, or controller in the current path failed. It is a common feature in high availability environments and is handled (usually automatically) by multipathing software. fallbacks This is a manual or automatic switch to an alternative method, when the primary option fails or is less preferred. FastCGI Fast Common Gateway Interface FastCGI is an extension of the {term}`CGI` protocol that starts a persistent FastCGI application process, allowing it to handle multiple requests instead of starting a new process for each request as a traditional CGI does. FC Fiber Channel FC is a storage networking protocol used for low-latency communication between a storage device and a node in a {term}`Storage Area Network (SAN) `. FHS Filesystem Hierarchy Standard FHS is a standard that defines the directory structure and contents in Linux and Unix-like operating systems. Fileset A fileset defines a group of directories that will be included when performing a backup job using Bacula. Related topic(s): * Storage filesystem A filesystem defines how data is organized, stored, and accessed on a storage device. Related topic(s): * Storage Fluentd Fluentd is a data collection platform that gathers events from a container for later analysis on other platforms. Related topic(s): * Observability, Containers FQDN Fully Qualified Domain Name A FQDN represents a complete name that specifies the exact location of a host within the {term}`DNS` hierarchy. Related topic(s): * Networking FreeIPA Free Identity, Policy, and Audit FreeIPA is an open-source security solution for Linux/Unix-like systems that stores user identities in an {term}`LDAP` directory, manages a {term}`CA`, and enables authentication, policy enforcement, and auditing through integrations with {term}`SSSD` and {term}`Kerberos`. Related topic(s): Security, OpenLDAP Freenode Freenode is an open-source {term}`Internet Relay Chat (IRC) ` platform used by many open-source communities for real-time discussions. frontend A frontend is a user-friendly interface for managing a complex system. - In firewall management, a frontend like `ufw` simplifies configuring `iptables`. - In QEMU/KVM graphics, a frontend is the virtual graphic adapter presented to the guest {term}`OS`, allowing it to process and store graphical output in memory. The guest OS treats it like a {term}`GPU`, while the host determines how to display the output using the {term}`backend`. - In LDAP, the frontend is a unique database that defines global default settings, such as who the admin user is, who can access database entries, or the limit on the number of search results. These settings apply to all LDAP databases inside {term}`slapd`, unless overridden. Related topic(s): * Virtualization and containers, Security, OpenLDAP. fsck File System Check `fsck` is a Linux/Unix-like system utility tool that checks for, and repairs, any {term}`filesystem` errors. Related topic(s): * Storage FULLTEXT FULLTEXT is an index type that allows for fast indexing and searching large quantities of text. It takes a sentence, splits it into words, and links them to row IDs. When a search query for a word is made, MySQL quickly looks up the row the word appear in, and retrieves all matching row IDs, rather than scanning the entire table. It can also find similar words using natural language processing. See also: * [Full-Text Search Functions](https://dev.mysql.com/doc/refman/8.4/en/fulltext-search.html) Related topic(s): * Databases FW Firmware Firmware is a software that runs before an operating system (OS) boots. - When a QEMU microvm starts, the firmware initializes minimal virtual hardware like allocating {term}`RAM` to the OS, and then loads the Linux kernel into memory. - In a physical device, firmware configures {term}`PCIe` devices like {term}`GPUs ` or network cards. ::: (terms_G)= ## G :::{glossary} gcplogs A logging driver that allows logs to be forwarded from a Docker container running in Google Cloud to the Google Cloud Logging service. Related topic(s): * Cloud, Containers, Observability gcrypt A cryptographic library that supports encryption, hashing, etc. for applications. Related topic(s): * Cryptographic libraries GDB GNU Debugger GDB traces the current execution of a program, with the aim of identifying any issues. Related topic(s): * Debugging gelf GELF Graylog Extended Log Format GELF is a logging driver that allow logs to be forwarded in {term}`JSON` format, but with extra unique fields. These logs are sent from a Docker container to a data collector platform like {term}`Graylog`, {term}`Logstash`, and {term}`Fluentd`. Related topic(s): * Containers, Observability GFS2 A shared-disk {term}`filesystem` that allows multiple servers to access a single disk. It uses a locking system to ensure that no two servers modify the same data simultaneously, thus preventing data corruption if one server fails. Additionally, fencing is used to isolate failed nodes, ensuring that their locks can be safely recovered. Related topic(s): * High availability, Storage GB Gigabyte (unit of measurement) 1 GB = 1024 bytes GID Group ID A GID is an identifier for a collection of users. It helps administrators enforce system or file access permissions on multiple users at once. Related topic(s): * Active Directory integration, Samba, Security, SSSD gitolite Gitolite is a tool installed on a central server for managing git repositories and controlling access to them, all via the command line. The central server becomes a git server. Related topic(s): * Backups and version control GKE Google Kubernetes Engine GKE is a managed Kubernetes service provided by Google cloud. GL Graphics Library A GL is an {term}`API` for interacting with a graphics card, enabling it to perform better rendering. Related topic(s): * Graphics GNU GNU's Not Unix A recursive acronym, GNU, is an operating system containing several free software packages. It can be used in combination with the Linux kernel. GnuTLS GNU's Not Unix Transport Layer Security GnuTLS is a GNU software package that secures data-in-transit by implementing the {term}`SSL`, {term}`TLS` and {term}`DTLS` protocol. Related topic(s): * Cryptography, Web services, OpenLDAP GPG GNU Privacy Guard GPG is a GNU software package that secures data-at-rest before sending it to a recepient. Related topic(s): * Security, Cryptography GPS Global Positioning System GPS is a collection of satellites that provides accurate time using radio signals from their atomic clocks. A GPS receiver plugged into a computer can sync with these satellites and generate {term}`PPS` signal, which delivers ultra-accurate time that applications can use as a time source. Related topic(s): * Networking GPSD GPS daemon This reads data from a GPS receiver and makes it available as a shared resource to multiple applications (e.g., {term}`Chrony`) to use for precise time synchronization. Related topic(s): * Networking GPU Graphics Processing Unit A GPU enhances graphics rendering for a computer and any virtual machines running inside of it. Related topic(s): * Graphics, Virtualisation and containers Graylog A data collector platform for storing, analysing, and interpreting logs. These logs are received from a {term}`gelf` logging driver in Docker. Related topic(s): * Containers GPO Group Policy Object A set of configuration rules used to manage and enforce security and system behaviours across users or computers within an Active Directory (AD) object. Related topic(s): Active Directory integration GSSAPI Generic Security Services Application Program Interface GSSAPI is a vendor-agnostic {term}`API` that uses an existing communication protocol to establish a secure communication between applications. It does this securely by verifying user credentials, ensuring that data being transmitted remains unchanged, preventing unauthorized access, and securely negotiating encryption keys. Related topic(s): * Cryptography GTK GIMP Toolkit GTK is a library used to create {term}`graphical user interfaces (GUIs) `. It provides a visual interface for interacting with the Bacula Director when managing backup-related operations. Related topic(s): * Graphics, Backups and version control GUI Graphical User Interface A GUI is a visual representation of operations within a computer. It is usually represented as icons rather than text only. GZIP GNU Zip GZIP is a {term}`GNU` software package used to reduce the file size of a backup. - When applied directly to files, it replaces the original file type with a `.gz` type. - When used in Bacula's {term}`fileset`, it reduces the storage size of backed-up directories within Bacula's storage volumes. - When used to reduce the size of a folder, it works in combination with a `tar` tool which first combines multiple files into a single archive, before applying GZIP's size-reduction technique. Related topic(s): * Backups and version control ::: (terms_H)= ## H :::{glossary} HA High Availability HA is the process of ensuring that a system is always up. To achieve this, a redundant system is set up that either takes over when the main system is down or runs alongside the main system to load-balance the workload. Related topic(s): * High availability HBA Host Bus Adapter HBAs are interface cards that connect a server to a storage device. Related topic(S): * Device mapper multipathing HMAC Hash-based Message Authentication Code A HMAC is a type of {term}`Message Authentication Code `. While a general MAC may use various techniques during combination, HMAC follows a structured way. When a message and its HMAC are sent, the receiver verifies the integrity by computing the HMAC again -- if the message is altered, the value will differ. Related topic(S): * Cryptography, Security HMC Hardware Management Console A HMC is used to manage IBM servers. It can handle tasks like configuring network settings, loading Ubuntu installation files and installing the {term}`OS`. hostgroup A group of backend web or database servers with similar configurations. Related topic(S): * Observability hostname A hostname identifies a server using a word rather than an {term}`IP address`. This makes it easier to remember. HOTP HMAC-based One-Time Password HOTP generates a one-time password by using the {term}`HMAC` algorithm in combination with a counter. When a client presents the {term}`OTP`, the server compares it with OTPs generated within a specific counter window to find a match. hotplug The process of adding or removing a device (USB, disks, etc.) while a virtual machine is running. HPB Host Physical Bits HPB are appended to the name of an Ubuntu machine type. It signifies that a virtual machine will use the same number of bits the host {term}`CPU` uses to point to physical memory. HPC High Performance Computing HPC is the use of multiple servers to improve the performance of a task. HSG High-availability Storage Group *Work in Progress* HSV Highly-available Storage Virtualization *Work in Progress* HTCP Hyper Text Caching Protocol *Work in Progress* HTML HyperText Markup Language *Work in Progress* HTTP HyperText Transfer Protocol *Work in Progress* HTTPD HyperText Transfer Protocol Daemon *Work in Progress* HTTPS HyperText Transfer Protocol Secure *Work in Progress* hugepage A huge page increases the page size on a host, and as a result, when virtual memory is allocated to an application, there are fewer page table entries required to map the virtual memory to physical memory. The page table entries are stored in Random Access Memory (RAM) and cached in the {term}`Translation Lookaside Buffer (TLB) `. HWE Hardware Enablement *Work in Progress* ::: (terms_I)= ## I :::{glossary} ICMP Internet Control Message Protocol *Work in Progress* ICP Internet Cache Protocol *Work in Progress* IDENT Identification Protocol *Work in Progress* IMAP Internet Messages Access Protocol *Work in Progress* init initialization *Work in Progress* I/O Input/Output *Work in Progress* IOMMU Input-Output Memory Management Unit *Work in Progress* IoT Internet of Things *Work in Progress* IP Internet Protocol *Work in Progress* IP address *Work in Progress* IPC Inter-Process Communication *Work in Progress* IPL Initial Program Load *Work in Progress* IPMI Intelligent Platform Management Interface *Work in Progress* IPP Internet Printing Protocol *Work in Progress* IPSec Internet Protocol Security *Work in Progress* iptables *Work in Progress* IPVS IP Virtual Server *Work in Progress* IQN iSCSI Qualified Name *Work in Progress* IRC Internet Relay Chat *Work in Progress* ISC Internet Systems Consortium *Work in Progress* iSCSI Internet Small Computer System Interface *Work in Progress* ISO International Organization for Standardization *Work in Progress* ISP Internet Service Provider *Work in Progress* ::: (terms_J)= ## J :::{glossary} jitter Jitter is the variation in delay or latency between when data packets are sent and when they are received over a network, causing irregular arrival times at the destination. This variation is often caused by network congestion, packet loss, poor hardware performance or differences in the path packets take. Related topic(s): * Networking journald `journald`, also known as `systemd-journald`, is a logging service developed by the {term}`systemd` project as part of the `systemd` suite. It collects and stores log messages from various sources, including `systemd` services, kernel messages, system logs, and application logs. `journald` stores logs in a binary format offering advantages, such as storage efficiency, searchability, and most especially structured logging. In containerized systems like Docker, it functions as a logging driver for containers. See also: * [the `journald.conf` manual page](https://manpages.ubuntu.com/manpages/noble/man5/journald.conf.5.html/) * [Docker `journald` documentation](https://docs.docker.com/engine/logging/drivers/journald/) for details on using journald as a logging driver Related topic(s): * Logging, Observability JSON JavaScript Object Notation This is a language-independent text format that uses conventions familiar to programmers of the C-family of languages, including C, C++, C#, Java, JavaScript, Perl, Python, and many others. Due to its simplicity, it is an ideal lightweight data interchange language. See also: * [The JSON website](https://www.json.org/json-en.html/) ::: (terms_K)= ## K :::{glossary} KDC Key Distribution Center *Work in Progress* keepalive *Work in Progress* Kerberos *Work in Progress* keypair *Work in Progress* keyring *Work in Progress* keysalt *Work in Progress* keyservers *Work in Progress* keytab *Work in Progress* Keytool *Work in Progress* KVM Kernel-based Virtual Machine *Work in Progress* ::: (terms_L)= ## L :::{glossary} LAN Local Area Network *Work in Progress* LDAP Lightweight Directory Access Protocol *Work in Progress* LDIF LDAP Data Interchange Format *Work in Progress* lightervisor *Work in Progress* Load-balancing *Work in Progress* localhost *Work in Progress* Logfiles *Work in Progress* Logstash *Work in Progress* Logwatch *Work in Progress* LPAR Logical Partition *Work in Progress* LSI Logic Systems Incorporated *Work in Progress* LTS Long-Term Support *Work in Progress* LU Logical Unit *Work in Progress* LUA Lua Scripting Language *Work in Progress* LUN Logical Unit Number *Work in Progress* LV Logical Volume *Work in Progress* LVM Logical Volume Manager *Work in Progress* LXC Linux Containers *Work in Progress* LXD Linux Container Daemon *Work in Progress* ::: (terms_M)= ## M :::{glossary} MAAS Metal as a Service *Work in Progress* MAC Message Authentication Code A MAC verifies that a message hasn't been modified during transmission by combining a shared secret key between the sender and receiver, and a hash function. MAC address *Work in Progress* manpage manual page *Work in Progress* MCE Machine Check Exception *Work in Progress* MDA Mail Delivery Agent *Work in Progress* mdev Minimal Device Manager *Work in Progress* metapackage *Work in Progress* METAR Meteorological Aerodrome Report *Work in Progress* microservices *Work in Progress* microVMs *Work in Progress* MOTD Message of the Day *Work in Progress* mountpoints *Work in Progress* MPIO Multipath Input/Output *Work in Progress* MSA Modular Smart Array *Work in Progress* MTA Mail Transfer Agent *Work in Progress* MTU Maximum Transmission Unit *Work in Progress* MUA Mail User Agent *Work in Progress* Multipass *Work in Progress* Multipath *Work in Progress* Multiview *Work in Progress* MySQL *Work in Progress* ::: (terms_N)= ## N :::{glossary} nameserver *Work in Progress* namespace *Work in Progress* NAS Network Attached Storage *Work in Progress* NAT Network Address Translation *Work in Progress* Netboot *Work in Progress* Netfilter *Work in Progress* Netplan *Work in Progress* NFS Network File System *Work in Progress* NFV Network Functions Virtualization *Work in Progress* nginx *Work in Progress* NIC Network Interface Card *Work in Progress* NIS Network Information Service *Work in Progress* NMI Non-Maskable Interrupt *Work in Progress* NRPE Nagios Remote Plugin Executor *Work in Progress* NSCQ Network System Configuration Queue *Work in Progress* NSS Name Service Switch *Work in Progress* NTP Network Time Protocol *Work in Progress* NTS Network Time Security *Work in Progress* NUMA Non-Uniform Memory Access *Work in Progress* Nvidia *Work in Progress* NVMe Non-Volatile Memory Express *Work in Progress* NVRAM Non-Volative Random Access Memory *Work in Progress* NVSwitch NVIDIA NVLink Switch *Work in Progress* ::: (terms_O)= ## O :::{glossary} OCF Open Cluster Framework *Work in Progress* OCFS Oracle Cluster File System *Work in Progress* OCI Open Container Initiative *Work in Progress* OCSP Online Certificate Status Protocol *Work in Progress* OpenLDAP *Work in Progress* OpenSC Open Smart Card *Work in Progress* OpenSSH *Work in Progress* OpenSSL *Work in Progress* OpenStack *Work in Progress* OpenSUSE *Work in Progress* OpenVPN *Work in Progress* OpenVZ *Work in Progress* OpenWRT *Work in Progress* OS Operating System *Work in Progress* OSA Open Systems Adapter *Work in Progress* OSI Open Systems Interconnection *Work in Progress* OTE Operational Test and Evaluation *Work in Progress* OTP One-Time Password *Work in Progress* OU Organisational Unit *Work in Progress* OverlayFS *Work in Progress* OVS Open vSwitch *Work in Progress* ::: (terms_P)= ## P :::{glossary} PAM Pluggable Authentication Module *Work in Progress* passthrough *Work in Progress* PB Petabyte (unit of measurement) 1 PB = 1024 {term}`TB` PCI Peripheral Component Interconnect *Work in Progress* PCIe Peripheral Component Interconnect Express *Work in Progress* PCS Pacemaker/Corosync Stack *Work in Progress* PDC Primary Domain Controller *Work in Progress* PEM Privacy Enhanced Mail *Work in Progress* Petitboot *Work in Progress* PgSQL *Work in Progress* PHP PHP: HyperText Preprocessor *Work in Progress* PID Process Identifier *Work in Progress* pingable *Work in Progress* PIV Personal Identity Verification *Work in Progress* PKCS Public-Key Cryptography Standards *Work in Progress* PKI Public Key Infrastructure *Work in Progress* pluggable *Work in Progress* PMD Poll Mode Driver *Work in Progress* POSIX Portable Operating System Interface (for UNIX) *Work in Progress* Postcopy *Work in Progress* Postfix *Work in Progress* Postgres PostgreSQL *Work in Progress* PostScript *Work in Progress* PowerShell *Work in Progress* PPA Personal Package Archive *Work in Progress* ppc PowerPC *Work in Progress* PPD PostScript Printer Description *Work in Progress* PPS Pulse Per Second *Work in Progress* Preboot *Work in Progress* preseed *Work in Progress* Prometheus *Work in Progress* proxy *Work in Progress* PTP Precision Time Protocol *Work in Progress* PTR Pointer Record *Work in Progress* PXE Preboot Execution Environment *Work in Progress* PXELINUX PXE Linux Loader *Work in Progress* ::: (terms_Q)= ## Q :::{glossary} QA Quality Assurance *Work in Progress* qdevice Quorum Device *Work in Progress* QEMU Quick Emulator *Work in Progress* qeth QDIO Ethernet *Work in Progress* quickstart *Work in Progress* ::: (terms_R)= ## R :::{glossary} RAM Random Access Memory *Work in Progress* rangesize *Work in Progress* rclone *Work in Progress* RDAC Redundant Disk Array Controller *Work in Progress* RDBMS Relational Database Management System *Work in Progress* RDN Relative Distinguished Name *Work in Progress* Redbook *Work in Progress* renderer *Work in Progress* REXX Restructured Extended Executor *Work in Progress* RFC Request For Comments *Work in Progress* rid Relative Identifier *Work in Progress* RISC-V Reduced Instruction Set Computing - Version Five *Work in Progress* Rocks *Work in Progress* ROM Read-Only Memory *Work in Progress* rootDN Root Distinguished Name *Work in Progress* rootfs Root File System *Work in Progress* routable *Work in Progress* RSA Rivest–Shamir–Adleman RSA is an asymmetric encryption algorithm *Work in Progress* rsnapshot *Work in Progress* rsync *Work in Progress* rsyslog *Work in Progress* RTC Real-Time Clock *Work in Progress* runtime *Work in Progress* ::: (terms_S)= ## S :::{glossary} SAN Storage Area Network *Work in Progress* sandboxed *Work in Progress* SANLOCK SAN Locking Daemon *Work in Progress* SASL Simple Authentication and Security Layer *Work in Progress* SBD Storage-Based Death *Work in Progress* sbin System Binaries *Work in Progress* schemas *Work in Progress* SCP Secure Copy Protocol *Work in Progress* Scrollback *Work in Progress* SCSI Small Computer System Interface *Work in Progress* SDN Software-Defined Networking *Work in Progress* sdx SCSI Desk (x) *Work in Progress* seccomp Secure computing mode *Work in Progress* SFTP SSH File Transfer Protocol *Work in Progress* SGI Silicon Graphics Inc. *Work in Progress* SHA Secure Hash Algorithm *Work in Progress* sharding *Work in Progress* Shell *Work in Progress* SHM Shared Memory *Work in Progress* Shorewall Shoreline Firewall *Work in Progress* SIDs Security Identifiers *Work in Progress* SIMD Single Instruction, Multiple Data *Work in Progress* slapd Standalone LDAP Daemon *Work in Progress* smartcard *Work in Progress* SMB Server Message Block *Work in Progress* SMS Short Message Service *Work in Progress* SMTP Simple Mail Transfer Protocol *Work in Progress* SMTPS SMTP Secure *Work in Progress* Snap *Work in Progress* snapd *Work in Progress* snapshot *Work in Progress* Snapstore *Work in Progress* SNMP Simple Network Management Protocol *Work in Progress* SOA Start of Authority *Work in Progress* Solaris *Work in Progress* SPC SCSI Primary Commands *Work in Progress* Splunk *Work in Progress* SRU Stable Release Update *Work in Progress* SSD Solid State Drive *Work in Progress* SSH Secure Shell *Work in Progress* SSI Server-Side Includes *Work in Progress* SSL Secure Sockets Layer *Work in Progress* SSO Single Sign-On *Work in Progress* SSSD System Security Services Daemon *Work in Progress* stateful *Work in Progress* STDIN Standard Input *Work in Progress* STDOUT Standard Output *Work in Progress* STDERR Standard Error *Work in Progress* STK Storake Tek *Work in Progress* storage *Work in Progress* subcommand *Work in Progress* Subiquity *Work in Progress* subnet subnetwork *Work in Progress* substring *Work in Progress* subvolume *Work in Progress* sudo superuser do *Work in Progress* superblock *Work in Progress* symlink *Work in Progress* syslog *Work in Progress* systemctl *Work in Progress* Systemd *Work in Progress* ::: (terms_T)= ## T :::{glossary} tasksel Task selector *Work in Progress* TB Terabyte (unit of measurement) 1 TB = 1024 {term}`GB` TCP Transmission Control Protocol *Work in Progress* TFTP Trivial File Transfer Protocol *Work in Progress* TGS Ticket Granting Service *Work in Progress* TGT Ticket Granting Ticket *Work in Progress* timedatectl *Work in Progress* timesyncd *Work in Progress* TLB Translation Lookaside Buffer TLB is a {term}`CPU` cache that stores recent page table entries. When the CPU translates a virtual address, it first checks the TLB. If the mapping is found, the translation is fast. If it's missing, the CPU retrieves the mapping from the page table in memory, which takes longer. TLS Transport Layer Security *Work in Progress* tmpfs Temporary Filesystem *Work in Progress* tmux Terminal Multiplexer *Work in Progress* topologies *Work in Progress* TOTP Time-based One-Time Password *Work in Progress* traceback *Work in Progress* Traceroute *Work in Progress* ttys Teletype Terminals *Work in Progress* TXT Trusted Execution Technology *Work in Progress* ::: (terms_U)= ## U :::{glossary} UDA Unified Data Architecture *Work in Progress* UDP User Datagram Protocol *Work in Progress* UEFI Unified Extensible Firmware Interface *Work in Progress* ufw Uncomplicated Firewall *Work in Progress* UID User Identifier *Work in Progress* UI User Interface *Work in Progress* unicast One-to-one communication unmount *Work in Progress* untrusted *Work in Progress* uptime *Work in Progress* URI Uniform Resource Identifier *Work in Progress* userspace *Work in Progress* USN Update Sequence Number *Work in Progress* usr Refers to the `/usr/` directory and stands for "Unix System Resources" UUIDs Universally Unique Identifiers *Work in Progress* ::: (terms_V)= ## V :::{glossary} vCPU Virtual CPU *Work in Progress* VCS Version Control System *Work in Progress* veth Virtual Ethernet *Work in Progress* VFIO Virtual Function I/O *Work in Progress* VFS Virtual File System *Work in Progress* VFs Virtual Functions *Work in Progress* VG Volume Group *Work in Progress* vGPU Virtual GPU *Work in Progress* virsh Virtual Shell *Work in Progress* VirtIO Virtual I/O *Work in Progress* virtual *Work in Progress* virtualization *Work in Progress* VLAN Virtual Local Area Network *Work in Progress* VM Virtual Machine *Work in Progress* VNC Virtual Network Computing *Work in Progress* VPN Virtual Private Network *Work in Progress* VRRP Virtual Router Redundancy Protocol *Work in Progress* vsftpd Very Secure FTP Daemon *Work in Progress* ::: (terms_W)= ## W :::{glossary} WAL Write-Ahead Logging *Work in Progress* WAN Wide Area Network *Work in Progress* WCCP Web Cache Communication Protocol *Work in Progress* Webserver *Work in Progress* winbind Windows Bind *Work in Progress* WireGuard *Work in Progress* WLAN Wireless Local Area Network *Work in Progress* WSGI Web Server Gateway Interface *Work in Progress* WWID World Wide Identifier *Work in Progress* ::: (terms_X)= ## X :::{glossary} xhtml Extensible HyperText Markup Language *Work in Progress* XML Extensible Markup Language *Work in Progress* ::: (terms_Y)= ## Y :::{glossary} YAML YAML Ain't Markup Language *Work in Progress* Yubikey *Work in Progress* ::: (terms_Z)= ## Z :::{glossary} zFCP zSeries Fibre Channel Protocol *Work in Progress* ZFS Zettabyte File System *Work in Progress* zpool ZFS Pool *Work in Progress* :::