🐧 Linux Essentials: An Easy-to-Understand Guide

📖 Index

📦 Package Management

RPM-Based (YUM & RPM)

YUM Commands

Command Purpose Example
yum update Update repos & packages yum update
yum search <package> Search package yum search httpd
yum install <package> Install package yum install nginx
yum check-update <package> Check if package needs updates yum check-update nginx
yum remove <package> Remove package yum remove nginx

RPM Commands

Command Purpose Example
rpm -ipv <file>.rpm Install package with progress & verbose rpm -ipv nano.rpm
rpm -qi <package> Query detailed info rpm -qi nano
rpm -e <package> Remove package rpm -e nano

Debian-Based (APT & dpkg)

APT Commands

Command Purpose Example
apt-get update Refresh package cache apt-get update
apt-cache search <package> Search for packages apt-cache search nginx
apt-get install <package> Install package apt-get install nginx
apt-get remove --purge <package> Remove package & config files apt-get remove --purge nginx

dpkg Commands

Command Purpose Example
dpkg -i <file>.deb Install Debian package dpkg -i nginx.deb
dpkg --get-selections List installed packages dpkg --get-selections
dpkg --purge <package> Completely remove package dpkg --purge nginx

💻 Command-Line Basics

Shell and Environment

  • Interactive Shell: CLI session.
  • Non-Interactive Shell: Background scripts/processes.
# Check current shell
echo $SHELL

# Command history
history      # Show all commands
history 10   # Last 10 commands
!10          # Execute command #10
!!           # Repeat last command
^typo^fix^   # Fix typo in previous command

Basic Linux Commands

Command Usage
cd Change directories (e.g., cd /home)
ls -la List files detailed, including hidden files
top View active processes
whoami Display current user

Command-Line Syntax

  • Command Structure: <command> [options] [arguments]

Example:

ls -l -a /var/log

Working with Variables

# Set and export variable
MY_VAR="Hello World"
export MY_VAR

echo $MY_VAR  # prints Hello World

File Globbing

Wildcard Meaning
* Match 0 or more chars
? Match exactly 1 char
[abc] Match a, b, or c

Examples:

ls *.txt        # all .txt files
ls file?.txt    # files like file1.txt, fileA.txt

🆘 Getting CLI Help

Using Man Pages

  • Quickly reference command details
man ls

Info Pages

  • Detailed documentation with hyperlinks
info coreutils

Quick Help Commands

Command Description Example
whatis <command> Brief command purpose whatis ls
apropos <keyword> Search keyword in manuals apropos file

📚 Examples and Practice

Example 1: Find large files in the home directory:

find ~/ -size +50M

Example 2: Compress and archive a folder:

tar -czvf archive.tar.gz folder/

Example 3: Search logs for errors:

grep -i error /var/log/*.log

✨ Practice Tip: Try running these commands on your system for hands-on experience.

Happy Learning! 🐧🚀