Linux on tplat

Distributions

Mon, 01 Jan 0001 00:00:00 +0000

Distributions#

A Linux distribution (distro) is an operating system built on the Linux kernel, bundled with userland tools, package management, and system utilities.

There are 600+ distributions, typically differentiated by:

Package management systems (e.g., APT, DNF, Pacman)
Default toolchains and utilities
Desktop environments / UI
Target use case (desktop, server, embedded, security)

Popular Distributions#

General Purpose#

Ubuntu — beginner-friendly, strong desktop ecosystem
Fedora — modern packages, upstream-focused
Debian — stability-focused

Enterprise#

Red Hat Enterprise Linux — commercial support, enterprise standard
CentOS — RHEL-compatible (community-driven variants)

Security / Offensive Tooling#

Kali Linux — extensive preinstalled security tools
Parrot OS — security, privacy, development focus
BlackArch — large penetration testing toolkit
Pentoo — Gentoo-based security distro
BackBox — Ubuntu-based security distro

Specialized / Other#

Raspberry Pi OS — optimized for ARM devices

Focus: Debian#

Overview#

Debian is a widely adopted distribution known for stability, reliability, and strict free software principles. It is commonly used across:

Permissions

Mon, 01 Jan 0001 00:00:00 +0000

Permissions#

Linux permissions control access to files and directories via a user–group–others model. Each filesystem object is associated with:

Owner (user)
Group
Permissions defining allowed operations

Users can belong to multiple groups, inheriting access rights accordingly.

Permission Types#

Symbol	Name	Meaning
`r`	Read	View file contents or list directory contents
`w`	Write	Modify file or directory contents
`x`	Execute	Run file or traverse directory

Permission Scope#

Permissions are defined for three classes:

Core Linux Commands

Mon, 01 Jan 0001 00:00:00 +0000

Core Linux Commands#

`man`#

Display manual pages for commands:

man ls

Comprehensive reference (syntax, options, behaviour)
Organized into sections (e.g., user commands, system calls)

`apropos`#

Search manual page descriptions by keyword:

apropos network

Useful when you don’t know the exact command name

External Resource#

explainshell — explains command syntax interactively

Common System Commands#

Command	Description
`whoami`	Print current user
`id`	Show user and group IDs
`hostname`	Get/set system hostname
`uname`	System/kernel information
`pwd`	Print current directory
`env`	Show or set environment variables

Networking#

Command	Description
`ifconfig`	Configure/view network interfaces (legacy)
`ip`	Modern network configuration tool
`netstat`	Network status (legacy)
`ss`	Socket inspection (modern replacement for netstat)

Process & System Inspection#

Command	Description
`ps`	Process status
`who`	Logged-in users
`lsof`	Open files by processes

Hardware Inspection#

Command	Description
`lsblk`	Block devices (disks)
`lsusb`	USB devices
`lspci`	PCI devices

File & Path Utilities#

`ls`#

List directory contents:

File Descriptors and Redirection

Mon, 01 Jan 0001 00:00:00 +0000

File Descriptors and Redirection#

Overview#

A file descriptor (FD) is a kernel-managed handle that represents an open I/O resource (file, socket, pipe, etc.). It provides a uniform interface for reading and writing data streams.

Windows equivalent: file handle

Standard File Descriptors#

By convention, every process starts with three predefined descriptors:

FD	Name	Description
`0`	STDIN	Standard input stream
`1`	STDOUT	Standard output stream
`2`	STDERR	Standard error stream

Basic Redirection#

Redirection operators control where data flows between streams and files.

SSH

Mon, 01 Jan 0001 00:00:00 +0000

SSH#

Secure Shell (SSH) refers to a protocol that allows clients to access and execute commands or actions on remote computers. On Linux-based hosts and servers, as well as other Unix-like operating systems, SSH is one of the permanently installed standard tools and is the preferred choice for many administrators to configure and maintain a computer through remote access. It is an older and very proven protocol that does not require or offer a graphical user interface (GUI). For this reason, it works very efficiently and occupies very few resources.

Regular Expressions (Regex)

Mon, 01 Jan 0001 00:00:00 +0000

Regular Expressions (Regex)#

Regular Expressions (regex) are patterns used to match and filter text. In Linux, they are commonly used with tools like grep, sed, and awk.

Practical note: Regex is dense but composable—focus on common patterns and reuse.

Core Constructs#

Pattern	Meaning
`.`	Any character
`*`	0 or more of previous
`+`	1 or more of previous
`?`	0 or 1 of previous
`^`	Start of line
`$`	End of line
`\b`	Word boundary
`\w`	Word character (`[a-zA-Z0-9_]`)
`[]`	Character class
`()`	Grouping
`\|`	OR operator

`grep` Modes#

Option	Description
`grep`	Basic regex
`grep -E`	Extended regex (preferred; enables `+`, `	`, etc.)
`grep -v`	Invert match

Exercises#

1. Exclude Lines Containing `#`#

cat /etc/ssh/sshd_config | grep -v "#"

-v → invert match (exclude comments)

2. Words Starting with `Permit`#

grep -E '\bPermit\w*' /etc/ssh/sshd_config

\bPermit → word starts with “Permit”
\w* → remaining characters

3. Words Ending with `Authentication`#

grep -E '\w*Authentication\b' /etc/ssh/sshd_config

\w* → prefix
Authentication\b → word ends with target

4. Lines Containing `Key`#

grep 'Key' /etc/ssh/sshd_config

Simple substring match (no regex needed)

5. Lines Starting with `Password` and Containing `yes`#

⚠️ Original pattern is incorrect (^Password|yes = OR logic)

Linux on tplat

Distributions

Distributions#

Popular Distributions#

General Purpose#

Enterprise#

Security / Offensive Tooling#

Specialized / Other#

Focus: Debian#

Overview#

Permissions

Permissions#

Permission Types#

Permission Scope#

Core Linux Commands

Core Linux Commands#

man#

apropos#

External Resource#

Common System Commands#

Networking#

Process & System Inspection#

Hardware Inspection#

File & Path Utilities#

ls#

File Descriptors and Redirection

File Descriptors and Redirection#

Overview#

Standard File Descriptors#

Basic Redirection#

SSH

SSH#

Regular Expressions (Regex)

Regular Expressions (Regex)#

Core Constructs#

grep Modes#

Exercises#

1. Exclude Lines Containing ##

2. Words Starting with Permit#

3. Words Ending with Authentication#

4. Lines Containing Key#

5. Lines Starting with Password and Containing yes#

`man`#

`apropos`#

`ls`#

`grep` Modes#

1. Exclude Lines Containing `#`#

2. Words Starting with `Permit`#

3. Words Ending with `Authentication`#

4. Lines Containing `Key`#

5. Lines Starting with `Password` and Containing `yes`#