Linux Study Guide: Chapters 1–7 & Shell Administration

Comprehensive vocabulary flashcards covering Linux fundamentals, installation, shell operations, filesystem administration, storage technologies, and process management.

Operating System (OS)

Software that manages computer hardware and software resources, sitting between the user, applications, and hardware to manage processes, memory, storage, devices, and interfaces.

Linux Kernel

The core component of the Linux operating system that controls hardware, manages memory and processes, loads OS components during startup, and communicates directly with device drivers.

Kernel Version Numbering

A three-part version structure consisting of major, minor, and revision levels; for example, in $5.18.16$, $5$ represents the major version, $18$ the minor version, and $16$ the revision.

Open Source Software (OSS)

Software whose source code is freely available for anyone to inspect, modify, enhance, and redistribute according to its specific license.

GNU General Public License (GPL)

The open-source license governing Linux that requires source code to remain available and mandates that any modified distributed versions must also remain licensed under the GPL.

Copyleft Licence

A licensing model, exemplified by the GPL, that incorporates an 'inheritance' property requiring all derivative or modified works to be distributed under the same licensing terms.

Linux Distribution (Distro)

A complete operating system package that combines the Linux kernel with system utilities, a package manager, a desktop environment, and pre-installed application software.

Live Media ISO

An installation image that boots and runs Linux entirely from RAM without writing to disk, allowing hardware verification prior to performing a permanent installation.

Basic Graphics Mode

A troubleshooting installation boot option that loads a generic, low-resolution video driver to resolve black or garbled screen issues caused by unsupported graphics hardware.

Media Testing

A pre-installation troubleshooting utility that performs a checksum verification on the installation media to catch corrupted downloads or bad USB writes before installation begins.

PATA Device Naming

The legacy naming scheme for Parallel ATA drives: Primary Master is hda, Primary Slave is hdb, Secondary Master is hdc, and Secondary Slave is hdd.

SATA / SCSI / SAS Device Naming

The naming convention where entire disks receive letters (such as sda, sdb, sdc) and individual partitions have appended numbers (such as sda1, sda2), located under /dev.

NVMe Device Naming

The naming standard for NVMe drives using controller and namespace numbers (e.g., nvme0n1 for the first disk) and an appended partition designator (e.g., nvme0n1p1 for the first partition).

Terminal

The communication channel—such as a console window, physical console, or SSH session—that passes keystrokes into the system and outputs text back to the user.

Shell

The user interface program operating inside a terminal that accepts command-line input, interprets user commands, and transmits instructions to the kernel for execution.

Bash (Bourne Again Shell)

The default command shell on most Linux systems, designed as an enhanced and backwards-compatible version of the original UNIX Bourne Shell.

GNOME Display Manager (GDM)

The graphical login program used by Fedora to authenticate users through a graphical screen before initializing the GNOME desktop environment.

Virtual Consoles (tty1–tty6)

Separate terminal sessions accessed via Ctrl+Alt+F1 through Ctrl+Alt+F6, where tty1 hosts the graphical login (GDM) and tty2 through tty6 provide text-based command-line logins.

Root vs Regular User Command Prompt

The visual indicator at the end of the shell prompt: a hash symbol (#) signifies administrative (root) privileges, whereas a dollar sign (\) indicates an unprivileged regular user account.

Command Options vs Arguments

Options modify how a command behaves (typically preceded by a dash $-$), whereas arguments provide specific targets or inputs (such as filenames or paths) without leading dashes.

su -

The switch-user command option that invokes a full login shell, loading the target user's home directory, environment variables, and PATH settings rather than retaining the original caller's environment.

Shell Metacharacters

Special keyboard characters (such as $$, ~, #, &, ;,

Single Quotes vs Double Quotes in Bash

Single quotes act as a complete 'off switch' by protecting all enclosed characters from shell interpretation, whereas double quotes suppress wildcards and word-splitting but still allow variable expansion ($) and command substitution.

Command Substitution

A shell feature using back quotation marks (`cmd`) where the enclosed command is executed first and its standard output is substituted directly into the outer command line.

man Command

The built-in documentation system that displays formatted manual pages describing a command's purpose, syntax (synopsis), options, authors, and related commands.

Manual Page Section 1 vs Section 8

Section 1 of the manual pages contains commands executable by any user, while Section 8 is reserved specifically for administrative and system management commands requiring root privilege.

apropos / man -k

Commands that query the indexed manual page database by keyword to display every manual page containing the search term in its name or summary description.

whatis Command

A documentation utility that displays only the single-line descriptive summary of a command from its manual page, without loading the full manual text.

info Command

A GNU hypertext documentation tool that displays structured, readable tutorial pages containing navigable hyperlinks between connected topics.

help Command

A built-in shell command used to view syntax, options, and usage information for commands implemented directly inside the shell itself rather than as separate binaries.

shutdown -P +4 vs shutdown -H +4

shutdown -P +4 completely powers off the machine after a 4-minute delay, whereas shutdown -H +4 halts the operating system without signaling the hardware BIOS ACPI to cut physical power.

Filesystem Root (/) vs Root Directory (/root)

The forward slash (/) represents the top-level root of the entire Linux directory tree, whereas /root is specifically the private home directory of the root administrator account.

Absolute Pathname vs Relative Pathname

An absolute pathname specifies an unambiguous file location starting from the root directory (/), while a relative pathname specifies a location originating from the current working directory.

Dot (.) and Dot-Dot (..)

Special directory entries automatically present in every directory, where a single dot (.) represents the current directory and a double dot (..) represents the directory one level above.

Magic Number

A distinctive signature embedded in the first few bytes of a file that Linux inspects to determine its true file format, independent of any file extension.

ls -l Fields

An 8-part output displaying: file type and permissions, hard link count, owner, group owner, size in bytes, last modification date and time, and the filename.

ls -F Type Indicators

Appended character symbols indicating file classifications: a forward slash (/) denotes a directory, an asterisk (*) denotes an executable file, and an at-sign (@) denotes a symbolic link.

tail -f

An option of the tail utility that keeps a file open and continuously prints newly appended lines to the terminal in real time, widely used for active log file monitoring.

more vs less

Terminal pagers for viewing long text files; less is newer, faster, and more capable than more, supporting bidirectional navigation and scrolling without reading the entire file first.

Command Pipe (|)

A shell mechanism that feeds the standard output of one command directly into the standard input of another command in memory without writing intermediate files to disk.

od (Octal Dump)

A command that safely displays raw data from binary or text files represented as base-8 (octal) numbers or other selectable formats.

strings Command

A diagnostic utility that searches binary files for sequences of printable characters and outputs them, useful for extracting embedded error messages or command names.

reset Command

A terminal restoration utility that reinitializes the terminal driver and resets display settings back to default, fixing screens garbled by raw binary output.

Shell Wildcard * vs Regexp *

As a shell wildcard, * matches any string of zero or more characters; as a regular expression, * matches zero or more occurrences strictly of the single preceding character.

grep Command

Global Regular Expression Print; a text search utility that scans files line-by-line for a specified pattern and prints all matching lines to standard output.

vi Editor Modes

The operational states of vi: Command mode (processes cursor movements and edits), Insert mode (enters typed text, entered via i), and Last-line mode (performs file saves and exits, entered via :).

Filesystem Hierarchy Standard (FHS)

An official organizational standard defining the structure, names, and expected contents of primary directories and files across Linux distributions.

/etc Directory

The standard system directory reserved strictly for machine-specific, static configuration files and system administration settings.

/proc and /sys Directories

Virtual pseudo-filesystems dynamically synthesized in RAM by the kernel to export runtime kernel data, process state tables, and hardware device configurations.

/media vs /mnt

/media provides automatic system mount points for removable media (like USB drives and DVDs), whereas /mnt is the traditional staging directory for manual, temporary filesystem mounts.

mv vs cp

mv updates a directory entry to rename or move data without duplicating it (requiring no recursive flag for directories), whereas cp allocates new storage and duplicates data (requiring -r to copy directories).

rm -rf

A destructive removal command that combines recursive traversal (-r) and force (-f) to irreversibly erase entire directory structures without confirmation prompts.

rm vs unlink

rm can delete multiple files simultaneously and traverse directories recursively with -r, whereas unlink deletes strictly one file at a time and cannot delete directories.

locate vs find

locate performs rapid queries against a prebuilt indexed database that may be slightly outdated, whereas find live-crawls the real filesystem directory tree to provide precise, current results.

PATH Variable

An environment variable containing an ordered list of directories separated by colons that the shell searches sequentially to find executable binary commands.

Hard Link

An additional directory entry sharing the identical inode and disk storage of an existing file; it cannot cross filesystems, cannot link directories, and keeps data accessible until all link references are removed.

Symbolic Link (Symlink)

A separate small pointer file containing the textual pathname of another target file or directory; it can cross filesystems and point to directories, but becomes dangling if its target is removed.

Directory Permissions (r, w, x)

Read (r) allows listing filenames within the directory; write (w) allows adding, renaming, or deleting entries within it; execute (x) allows entering the directory (cd) and accessing its contents.

Non-Additive Permission Evaluation

The security rule stating that Linux evaluates permissions in strict order (User, Group, Other) and halts at the first matching category, meaning owner permissions always override group permissions.

Numeric Permissions

The octal representation of file rights calculated by summing $r=4$, $w=2$, and $x=1$ for each class; for example, $644$ yields rw-r--r-- and $755$ yields rwxr-xr-x.

Access Control List (ACL)

An advanced filesystem permissions extension configured via setfacl and getfacl that assigns specific permissions to individual named users or groups outside the standard owner/group/other model.

ACL Mask

A boundary attribute in an Access Control List that sets the absolute maximum permission ceiling that any extended user or group ACL entry can grant.

Immutable Attribute (+i)

A filesystem attribute set via chattr +i that prevents a file from being edited, deleted, renamed, or overwritten by any user on the system, including root.

Character Device vs Block Device

Character devices transfer information stream-by-stream one character at a time (e.g., terminals), whereas block devices buffer and transfer data in fixed chunks or blocks (e.g., hard drives).

Mounting

The process of attaching a filesystem on a physical storage device to a specific directory (the mount point) within the unified Linux directory hierarchy.

Compression Ratio

The proportion of file size saved during compression, mathematically defined as $\text{Compression ratio} = 100\% - \text{compressed percentage}$.

tar (Tape Archive)

A classic utility used to bundle multiple files and directory hierarchies into a single archive file, using options such as -c (create), -x (extract), -v (verbose), and -f (file).

Storage Area Network (SAN)

A dedicated, high-speed, centralized storage network that provides block-level network storage access to multiple interconnected enterprise servers.

Uninterruptible Power Supply (UPS)

An electrical backup device with battery capacity designed to sustain server operations temporarily during outages, enabling orderly, corruption-free system shutdowns.

Type 1 vs Type 2 Hypervisors

Type 1 hypervisors execute bare-metal directly on the host hardware for maximum performance and efficiency, while Type 2 hypervisors run inside a conventional host operating system as an application.

SCSI ID vs LUN

A SCSI ID (Target ID) uniquely identifies a hardware controller or storage device on a SCSI bus, while a Logical Unit Number (LUN) identifies an individual sub-device or volume behind that target.

Serial Attached SCSI (SAS)

A modern serial point-to-point enterprise storage interface replacing parallel SCSI, capable of transferring data at speeds up to approximately $22.5\,\text{Gb/s}$.

RAID Levels (0, 1, 5, 6)

Storage array configurations where RAID 0 stripes without redundancy, RAID 1 mirrors data across drives, RAID 5 uses distributed parity tolerating 1 failure, and RAID 6 uses dual parity tolerating 2 failures.

ZFS (Zettabyte File System)

An integrated enterprise filesystem and logical volume manager that offers continuous checksumming, self-healing data repair, multi-disk pooling via zpool, and high fault tolerance.

Standard File Descriptors (0, 1, 2)

The default Linux I/O channels where file descriptor 0 represents Standard Input (stdin), 1 represents Standard Output (stdout), and 2 represents Standard Error (stderr).

Output Redirection (> vs >>)

The single greater-than operator (>) redirects standard output to a file, completely overwriting its prior contents, whereas double greater-than (>>) appends output to the end of the file.

User Process vs Daemon Process

A user process runs interactively inside a specific terminal session initiated by a user, whereas a daemon runs detached in the background to provide continuous system or network services.

PID vs PPID

Process ID (PID) is the unique numeric integer assigned by the kernel to identify a running process; Parent Process ID (PPID) is the PID of the ancestor process that spawned it.

init / systemd Process

The initial user-space process spawned directly by the kernel at system startup, always assigned $\text{PID } 1$ and $\text{PPID } 0$, acting as the ancestor of all other running processes.

SIGTERM (15) vs SIGKILL (9)

Signal 15 (SIGTERM) politely requests a process to terminate cleanly and save its state, while signal 9 (SIGKILL) is an uncatchable command handled directly by the kernel that terminates a process immediately.