How to Use pwd, cd, and ls
Learn with Linny-senpai and Lina! Master pwd (location), ls (list), and cd (move) - the 3 essential commands for beginners.
Read More →⚡ Tutorials
A collection of practical Linux tutorials for progressive learning. From basic commands to advanced techniques, explained in detail with rich examples.
🚀 Basic Operations
Beginner
How to Use mkdir, touch, and echo
Learn with Linny-senpai and Lina! Master mkdir (create directories), touch (create files), and echo/cat (view contents).
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How to Use cp, mv, and rm
Learn basic file operations: creation, editing, copying, moving, and deletion. Includes introduction to text editor basics.
Read More →🔐 Permissions & Process Management
Intermediate
How to Use chmod and chown
Detailed explanation of file and directory permissions, chmod, chown, umask and other permission-related commands.
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How to Choose Between chmod, chown, and sudo
Practical learning of advanced permission management including special permissions, ACL, and security configuration.
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Fixing Permission Denied at the Root Cause
Detailed explanation of permission configuration best practices and real-world examples used in system administration.
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How to Use ps, top, and kill
Learn process concepts and process management commands including ps, kill, jobs, and nohup.
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Linux Process Management in Practice
Learn practical techniques including system monitoring, performance tuning, and troubleshooting.
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Permission Denied Fix
How to quickly diagnose Permission denied errors. Learn when to use chmod, chown, or sudo, and avoid common mistakes.
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SSH Connection Troubleshooting Checklist
SSH connection troubleshooting checklist. Learn how to fix Permission denied (publickey), Host key verification failed, and Connection timeout issues.
Read More →💪 Advanced Techniques
Advanced
How to Use head, tail, and Pipes
Learn advanced file operation techniques including links, compression/decompression, and backup technologies.
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How to Use find, grep, and awk
Practical learning of advanced file search and processing techniques using find, grep, awk. Aimed at professional-level mastery.
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How to Use find, grep, and awk - Basics
Systematic learning of basic file search and text processing commands.
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grep and awk Advanced Techniques
Learn advanced techniques including complex search conditions, regular expressions, and awk programming.
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How to Combine find, grep, and awk
Detailed explanation of practical use cases and best practices used in real-world work.
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find, grep, and awk Exercises
Detailed learning of professional-level advanced techniques and optimization methods.
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How to Write Shell Scripts
Systematic learning of shell script writing basics, variables, control structures, and functions.
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Shell Scripting in Practice
Learn practical shell script creation methods, debugging techniques, and performance optimization.
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Investigating "No Space Left on Device"
How to quickly identify what's consuming disk space when Ubuntu server reports "disk full". Learn df/du usage and log bloat troubleshooting.
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journalctl Basics: Log Investigation
Learn how to check logs in Ubuntu (systemd) environments. Master filtering by time, service, and priority level for effective troubleshooting.
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tar Basics: Compression, Extraction & Avoiding Mistakes
Learn tar command for compression, extraction, and listing contents. Understand .tar.gz/.tgz/.tar differences and how to prevent extraction accidents.
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Safe find Usage: Avoid Deletion Accidents
Learn safe find command usage to avoid deletion accidents. Master the list-first approach, count verification, and safe deletion with -print0/xargs -0.
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Docker Disk Usage Investigation
How to identify disk usage growth in Docker environments. Use docker system df to determine if images/containers/volumes are the cause.
Read More →🔧 Practical Troubleshooting
Search by SymptomFor when you're stuck right now. Find solutions quickly by symptom.
🌐 Connection & Network
SSH Connection Troubleshooting Checklist
How to fix Permission denied (publickey), Host key verification failed, Connection timeout
Find Solution →DNS Name Resolution Troubleshooting
Investigation steps when "name resolution fails". Using dig/host/nslookup and checking /etc/resolv.conf
Find Solution →Port Connectivity Troubleshooting
Investigation steps when "can't connect". Testing with nc/telnet/curl, checking port status with ss/netstat
Find Solution →ufw / Firewall and SSH Connection
Causes and recovery steps when "SSH stopped working after ufw enable"
Find Solution →🔒 Permission Denied Errors
Permission Denied Fix
When to use chmod, chown, or sudo and how to avoid common mistakes
Find Solution →📊 Server Running Slow
CPU High Load Troubleshooting
Identify high CPU processes with top/htop, understanding load average
Find Solution →Memory Shortage Troubleshooting
Check memory usage with free/top, verify OOM Killer, swap management
Find Solution →Disk I/O Troubleshooting
Check I/O load with iostat/iotop, identify disk I/O bottlenecks
Find Solution →💾 Disk Full
Investigating "No Space Left on Device"
Using df/du to identify space consumption and log bloat
Find Solution →Docker Disk Usage Investigation
Using docker system df to identify images/containers/volumes
Find Solution →⚠️ Avoiding File Operation Accidents
Safe find Usage: Avoid Deletion Accidents
List first → verify count → delete. Safe deletion with -print0/xargs -0
Find Solution →tar Basics: Avoiding Common Mistakes
Prevent extraction accidents and file overwrites
Find Solution →scp/rsync Basics: Safe File Transfer
When to use scp vs rsync, pre-transfer verification, bandwidth limiting
Find Solution →📋 Investigating Logs
Nginx/Apache Log Analysis
Reading access and error logs, aggregating with awk/grep, common errors
Find Solution →⚙️ Service Management
systemctl Basics: Service Management
Using start/stop/restart/status/enable/disable, checking service status
Find Solution →cron Basics: Scheduled Task Management
Writing crontab entries, checking logs, troubleshooting when tasks don't run
Find Solution →🐧 Master Skills Through Practice!
After learning the theory, practice using actual commands. You can learn experientially at Penguin Gym Linux.