Linux Foundation glossary
Key Linux Foundation certification terms and acronyms.
Definitions are AI-assisted and reviewed for general accuracy — verify critical details against Linux Foundation's official documentation.
ACLAccess Control List
An extended permission mechanism allowing fine-grained file access rights beyond standard owner/group/other POSIX permissions.
cgroupsControl Groups
A Linux kernel mechanism that limits, accounts for, and isolates CPU, memory, and I/O resource usage per process group.
cron
A time-based job scheduler daemon in Linux that executes commands or scripts at specified intervals defined in a crontab file.
DHCPDynamic Host Configuration Protocol
A network protocol that automatically assigns IP addresses and other network configuration parameters to client hosts.
DNSDomain Name System
A hierarchical naming system that resolves human-readable hostnames to IP addresses on a network.
ext4Fourth Extended Filesystem
A widely used Linux journaling filesystem supporting large files, extents, and improved performance over ext3.
GRUBGrand Unified Bootloader
The default bootloader for most Linux distributions, responsible for loading the kernel and initrd at system startup.
inode
A data structure on a Linux filesystem that stores metadata about a file, such as permissions, ownership, and data block pointers.
iptables
A user-space utility for configuring the Linux kernel firewall by defining rules for packet filtering and NAT.
journald
A systemd component that collects and stores structured binary log data from the kernel, services, and applications.
LVMLogical Volume Manager
A device mapper framework that provides logical volume management for flexible disk storage allocation on Linux.
namespace
A Linux kernel feature that isolates system resources such as PIDs, network interfaces, and mount points per process group.
NFSNetwork File System
A distributed file system protocol that allows a client to mount and access remote directories over a network.
PAMPluggable Authentication Modules
A framework providing a flexible mechanism for authenticating users through configurable, stackable library modules.
POSIXPortable Operating System Interface
A family of IEEE standards defining API, shell, and utility interfaces to ensure compatibility across Unix-like operating systems.
RAIDRedundant Array of Independent Disks
A storage technology that combines multiple disks for redundancy or performance using levels such as RAID 0, 1, and 5.
rsync
A fast file synchronization utility that transfers only changed file blocks between local or remote locations.
runlevel
A mode of operation in SysV init that defines which system services are running; largely replaced by systemd targets.
SELinuxSecurity-Enhanced Linux
A Linux kernel security module that enforces mandatory access control policies to restrict process and file access.
SSHSecure Shell
A cryptographic network protocol used for secure remote login, command execution, and file transfer between hosts.
sudoers
The configuration file (/etc/sudoers) that defines which users or groups may execute commands with elevated privileges via sudo.
swap
A designated disk area used by the Linux kernel to move inactive memory pages when physical RAM is insufficient.
systemd
A system and service manager for Linux that initializes the system, manages services, and handles dependencies during boot.
umask
A value that determines the default permission bits subtracted from newly created files and directories.
XFS
A high-performance 64-bit journaling filesystem used as the default filesystem in RHEL/CentOS, supporting large files and parallel I/O.