Linux & Open Source glossary

This open-source and Linux glossary defines, in one sentence, the key terms from our courses: kernel, distribution, shell, packages, certifications… Each definition stands on its own and, where relevant, points to the related course.

Open source

Open-source software publishes its source code, freely viewable, modifiable and redistributable under its licence (GPL, MIT…).

Linux

Linux is a free operating system, very common on servers, available in many distributions. See our Linux / Red Hat courses.

Distribution (distro)

A distribution bundles the Linux kernel, tools and a package manager into a ready-to-use system (Red Hat, Debian, Ubuntu…).

Red Hat / RHEL

Red Hat Enterprise Linux (RHEL) is the leading enterprise Linux distribution, with dedicated support and certifications.

Kernel

The kernel is the core of the system: it manages the hardware, memory and processes, bridging hardware and software.

Shell / Bash

The shell is the command-line interpreter; Bash is the most common one on Linux.

Shell script

A shell script automates a sequence of commands in an executable file. See the shell scripting & automation course.

Package & package manager

A package is ready-to-install software; the manager (yum/dnf, apt) installs it and resolves dependencies from repositories.

Repository

A repository is an online source of vetted packages from which the system downloads and updates its software.

systemd & services

systemd manages system startup and services (daemons): start, stop, dependencies and logging.

Permissions

Permissions (read, write, execute) control access to files and directories per user and group.

root & sudo

root is the all-powerful admin account; sudo runs a single command with those privileges, in an audited way.

SSH

SSH opens an encrypted connection to administer a server remotely from the command line.

SELinux

SELinux is a Red Hat security module that enforces mandatory access control to confine processes.

LVM

LVM (Logical Volume Manager) manages storage as flexible logical volumes, resizable without reinstalling.

cron

cron schedules recurring tasks (backups, scripts) to run automatically at set times.

RHCSA / RHCE

RHCSA and RHCE are Red Hat administrator certifications, recognised in the industry. See the RHCSA preparation.

LPIC

LPIC (Linux Professional Institute Certification) is a distribution-agnostic Linux certification with several levels. See LPIC-1.

Yocto & embedded

Yocto is a project to build custom Linux distributions for embedded systems. See the Yocto course.