Enterprise Linux Glossary

This glossary collects common terms from the AlmaLinux and Enterprise Linux (EL) ecosystem, arranged alphabetically for easy lookup. Proper nouns retain their standard capitalization.

A

ABI (Application Binary Interface) / Binary Compatibility: An ABI is the binary-level interface contract between a program and libraries and the kernel. "Binary compatibility" means a binary program compiled for one distribution can run on another without recompilation. AlmaLinux maintains binary compatibility with RHEL; starting with RHEL 10, AlmaLinux moved to an ABI-compatible model, guaranteeing a consistent application binary interface rather than pursuing a bit-for-bit clone.

ABI compatibility: Compared with a "bit-for-bit clone," ABI compatibility only guarantees that the binary interface matches upstream, allowing differences in the underlying implementation. This lets AlmaLinux more flexibly backport security patches and hardware support while ensuring software built for RHEL runs correctly.

AlmaLinux: A free, open-source, enterprise-grade Linux distribution maintained by the AlmaLinux OS Foundation. As one of the community successors to CentOS Linux, it is compatible with RHEL. The latest stable versions are 10.2 and 9.8 (released in May 2026).

AppStream / BaseOS repositories: The two core repositories of EL-family distributions. BaseOS provides the base packages that form the core of the operating system, with a lifecycle matching the major system version; AppStream provides applications, runtimes, databases, web services, and more, and supports module streams to offer different versions.

B

Beta / RC (Release Candidate): Stages before a software release. Beta is for early public testing — mostly feature-complete but possibly buggy; RC (Release Candidate) is a near-final version that can be released as the general availability (GA) build if no major issues remain.

Btrfs: A copy-on-write (CoW) filesystem supporting snapshots, subvolumes, and built-in RAID. RHEL and AlmaLinux do not use Btrfs by default; the default filesystem is XFS.

Buildah: A command-line tool for building OCI-standard container images, often used together with Podman, capable of building images in daemonless, rootless environments.

C

CentOS Stream: A rolling-release distribution maintained by Red Hat, positioned between Fedora and RHEL, and serving as the upstream for the next RHEL minor release. It is released ahead of RHEL and is not a bit-for-bit match for any released RHEL.

Cockpit: A web-based graphical server management tool that lets you manage system services, networking, storage, containers, logs, users, and more through a browser — well suited to administrators not comfortable with the command line.

D

DNF: The default package manager (Dandified YUM) in EL 8 and later, used to install, upgrade, remove, and query RPM packages and automatically resolve dependencies. It is the successor to the earlier yum.

E

ELevate / leapp: The in-place upgrade solution provided by AlmaLinux. leapp is the underlying upgrade framework, and ELevate extends it to support cross-distribution, cross-major-version in-place migration between EL distributions such as CentOS, AlmaLinux, Rocky Linux, and Oracle Linux.

EOL / Lifecycle: EOL (End of Life) is the date when a version stops receiving updates and security patches. Each major AlmaLinux version typically provides about 10 years of support; for example, 8.10 is the final release in the AlmaLinux 8 series.

EPEL (Extra Packages for Enterprise Linux): An additional software repository maintained by the Fedora community for RHEL and compatible distributions, providing many open-source packages not found in the base repositories.

Enterprise Linux (EL): A general term for the family of Linux distributions based on RHEL, aimed at enterprise production environments and emphasizing long-term stability and compatibility. AlmaLinux, Rocky Linux, Oracle Linux, and others all belong to this family.

F

firewalld: The default dynamic firewall management tool in the EL family, organizing rules by "zones" and using nftables underneath. It can adjust rules dynamically without interrupting existing connections.

G

GA (General Availability): The stable version of software released to all users for production use after testing, distinct from pre-release stages such as Beta and RC.

K

Kickstart: A mechanism for unattended, automated installation of EL systems via an answer file. A Kickstart file describes configuration such as partitioning, networking, packages, and users, and can be used to deploy systems consistently at scale.

M

Module Streams: A mechanism in AppStream that allows multiple versions (streams) of the same software to coexist on the same system for selection — for example, different versions of PHP, Node.js, or databases — each with its own independent lifecycle.

N

NetworkManager: The default network configuration and management service in the EL family, providing unified management of wired, wireless, VPN, and other network connections, operable via nmcli (command line) or nmtui (text interface).

O

Oracle Linux: A RHEL-compatible enterprise distribution maintained by Oracle, offering both the Red Hat Compatible Kernel (RHCK) and Oracle's own UEK kernel.

P

Podman: A daemonless container engine whose commands are highly compatible with Docker, supporting rootless container execution. It is the default container tool in the EL family.

R

RHEL (Red Hat Enterprise Linux): A commercial enterprise Linux distribution developed by Red Hat, serving as the baseline and upstream for the entire EL ecosystem. AlmaLinux maintains compatibility with it.

Rocky Linux: A free, RHEL-compatible enterprise distribution maintained by the Rocky Enterprise Software Foundation, also one of the community successors to CentOS Linux.

RPM (RPM Package Manager): The software package format (.rpm) and underlying package management tool used by the EL family. DNF provides dependency resolution and repository management on top of it.

S

SBOM (Software Bill of Materials): A list of all components, libraries, and their versions and sources in a piece of software, used for supply-chain security auditing and vulnerability tracking.

SCAP / OpenSCAP: SCAP (Security Content Automation Protocol) is a standard for security-compliance automation; OpenSCAP is its open-source implementation, which can scan systems and check compliance against security baselines (such as CIS or DISA STIG).

SELinux (Security-Enhanced Linux): A mandatory access control (MAC) security module built into the kernel that restricts process permissions through security contexts and policies. It is enabled and set to Enforcing mode by default in the EL family.

systemd: The default init system and service manager in the EL family, responsible for system startup, service management, logging (journald), timers, and more, controlled via systemctl.

X

XFS: A high-performance, scalable journaling filesystem that is the default filesystem on RHEL and AlmaLinux. It suits large files and high-concurrency scenarios and supports online growth.

x86-64-v2 / x86-64-v3: Microarchitecture baseline levels of the x86-64 architecture. v2 roughly corresponds to processors from around 2009 onward, while v3 additionally requires instruction sets such as AVX2. AlmaLinux 10 raised its baseline requirement and provides an x86-64-v2 variant for older hardware.