Frequently Asked Questions (FAQ)

Yes, all basic features are completely free.

• Virtual terminal environment learning
• All learning courses
• Progress management and badge system
• Tutorial articles

We may offer premium plans with advanced features in the future, but basic learning features will remain free.

Currently, user registration is not required.

Learning progress is saved in your browser's localStorage, allowing you to resume learning from where you left off on the same browser and device.

Note: Progress won't be saved if you delete browser data or use private mode.

The service works on all major browsers:

• Google Chrome (Version 90+ recommended)
• Mozilla Firefox (Version 88+ recommended)
• Safari (Version 14+ recommended)
• Microsoft Edge (Version 90+ recommended)

Internet Explorer is not supported. For the best learning experience, please use the latest browser version.

Yes, the responsive design supports mobile devices.

Recommended environment:

• Screen size: 5 inches or larger
• iOS 13 or later (Safari)
• Android 8 or later (Chrome)

However, for command input learning, we recommend using a physical keyboard.

Basic learning features work, but progress saving has limitations:

• Available: Terminal operations, exercise execution
• Limited: Learning progress, badge saving

For continuous learning, we recommend using normal mode.

Partial offline use is possible:

• Required: Internet connection for first access
• Cache: Basic features saved in browser are usable
• Recommended: Online environment for latest features

Lessons are organized in three levels:

• Beginner (🟢): Basic commands, file operation basics
• Intermediate (🟡): Permission management, process management, advanced operations
• Advanced (🔴): Shell scripting, advanced file operations

Progressive learning allows you to develop skills naturally.

Penguin Gym Linux features:

• Browser-based: No installation or setup required
• Safe environment: No impact on actual systems
• Japanese & English support: Easy-to-understand explanations
• Practice-focused: Hands-on command operations over theory
• Progressive learning: Systematic curriculum by level

Linux is a free, open-source operating system:

• Windows/Mac: Commercial OS, GUI-focused
• Linux: Open source, excels at command-line operations
• Features: High stability, widely used in servers and development
• Learning benefits: Essential skill in IT industry, advantageous for career

Types (variations) of Linux:

• Ubuntu: Beginner-friendly, desktop-oriented
• CentOS/RHEL: Commonly used in enterprise servers
• Debian: Stability-focused, server use
• Alpine: Lightweight, popular in container environments

Basic commands are common across all types, so start learning commands first.

Difference in operation methods:

• GUI (Graphical User Interface): Click icons with mouse
• CLI (Command Line Interface): Input commands with keyboard

CLI advantages:

• Fast and accurate operations
• Easy automation and scripting
• Essential for remote server operations
• Lower memory usage

Important concepts in Linux directory structure:

• Root directory (/): System-wide top level, origin of all files
• Home directory (~): User's personal workspace (e.g., /home/username)

Commonly used directories:

• /home: Collection of user home directories
• /var: Variable data like log files
• /etc: System configuration files
• /usr: User programs

Methods to specify file or directory locations:

• Absolute path: Complete path starting from root (/)
• Relative path: Path from current location

Usage examples:

• Absolute: /home/user/documents/file.txt
• Relative: ./documents/file.txt (from current location)
• Parent directory: ../ (one level up)

Use relative paths for short operations, absolute paths when certainty is needed.

Commonly confused concepts:

• Terminal: The black screen (application)
• Shell: Program that interprets and executes commands

Major shells:

• bash: Most common, standard on many Linux systems
• zsh: Extended version of bash, standard on macOS Catalina+
• fish: User-friendly features

This service provides a bash-based environment.

Yes, absolutely no problem!

This service is designed for beginners:

• Progressive curriculum from basics
• Detailed explanations with hint features
• Safe virtual environment (no system impact even with mistakes)
• Getting Started guide

We recommend starting with "Basic Commands".

Learning pace varies individually, but we recommend progressive learning:

• Basic commands: Daily continuous practice is important
• File operations: Progressive learning after mastering basics
• Permission/Process management: More advanced skill level
• Shell scripting: Application-level techniques

Continuous learning is most important. We recommend daily practice, even if brief.

Yes, we recommend this order:

1. Basic Commands Introduction
2. File Operations Guide (Basics)
3. File Operations Guide (Advanced)
4. Permission Management Basics
5. Permission Management (Advanced)
6. Permission Management (Practical)
7. Process Management Introduction
8. Shell Scripting Basics

Understanding each stage thoroughly before proceeding is important.

The badge system visualizes learning achievements. Currently 13 types of badges are available:

• First Command: Clear first lesson
• Basic Master: Master 5 basic commands
• File Operation Expert: Master file operation commands
• Permission Management Master: Master permission management commands
• 10/20 Commands Achievement: Clear a certain number of lessons
• Complete Mastery: Clear all lessons

Other badges include Process Manager, Explorer, System Administrator for specific skill areas. Badges are for motivation, not skill certification.

These methods are effective:

• Repetitive practice: Daily continuation, even if brief
• Actual use: Hands-on command input over theory
• Cheat sheets: Note frequently used commands
• Progressive learning: Systematic learning from basics to advanced
• Learn from errors: Challenge without fear of mistakes

Especially with this service, you can practice fearlessly in a safe environment.

Common beginner challenges and solutions:

• Path concept: Understand absolute vs relative paths
• Permission errors: Check permission settings for Permission denied
• Command options: Start with basic forms first
• Case sensitivity: Linux strictly distinguishes uppercase/lowercase
• Space importance: Required between commands and arguments

Each lesson has hint features, so use them when stuck.

Yes, programming experience is not required:

• Independent skill: Separate skill domain from programming
• Basics are simple: Basic commands use everyday words
• Progressive acquisition: Advance naturally from beginner to advanced
• Practical focus: Emphasize actual operations over theory

Rather, Linux skills become the foundation for future programming learning.

We recommend gradual transition:

• After basic commands: Understanding ls, cd, pwd, cat, etc.
• After file operations: Safely using cp, mv, rm
• After permission concepts: Understanding chmod basics

Real environment preparation:

• Virtual environment with VirtualBox or VMware
• WSL (Windows Subsystem for Linux) utilization
• Cloud Linux servers (AWS, GCP, etc.)

Efficient command history techniques:

• Up arrow key: Recall previous command
• history command: Check past command history
• ! (exclamation): Execute command by history number
• Ctrl+R: History search (in real environment)

This service also has basic history features for re-executing long commands.

Learning pace guide:

• 1 week: Master basic commands (ls, cd, pwd)
• 2-3 weeks: Master general file operations
• 1 month: Understand permission management basics
• 2-3 months: Use Linux in daily work

Tips for continuity:

• Daily 15-30 minute short sessions
• Value progress over perfection
• Use badge acquisition as motivation

Linux learning is highly valuable in the modern IT industry:

• Web development: Many production servers run Linux
• Infrastructure engineer: Essential skill for server management
• DevOps: Indispensable for automation and CI/CD
• Cloud engineer: Linux operations on AWS, Azure, GCP
• Data engineer: Utilized in data processing pipelines

Starting from basic commands and progressively acquiring system management skills leads to career advancement.

Frequently used commands in professional settings:

• Navigation: cd, ls, pwd (most frequent)
• File operations: cat, less, tail, grep
• Process management: ps, top, kill
• Network: ssh, curl, wget
• Permissions/System: sudo, chmod, chown
• Text processing: awk, sed, sort, uniq

Combining these commands enables efficient work.

Impact on career change by level:

• Basic level (1-2 months): Show engineering aspiration
• Intermediate level (3-6 months): Valued as junior engineer
• Advanced level (6+ months): Expected as immediate contributor

Career change utilization:

• Specify Linux skills in portfolio
• Demonstrate command operations in technical interviews
• Use as proof of self-learning ability

Progressive certification recommendations:

• LPIC-1: Linux Professional Institute Certification Level 1
• LinuC Level 1: Japanese Linux certification
• CompTIA Linux+: International Linux certification

Certification preparation after basics:

• Master basic commands with this service
• Practice in real environments
• Study with certification books and practice tests
• Take the actual exam

Essential skills in modern web development:

• Production environment: Many web servers run Linux
• Deployment: Command-line operations required
• Troubleshooting: Log checking, process management
• Docker: Container technology based on Linux
• CI/CD: Linux used in automation pipelines

Minimum skills:

• Basic commands (ls, cd, cat, grep)
• File editing (vi/nano)
• Process management (ps, kill)
• Log checking (tail, less)

High-value skill for freelancers:

• Rate increase: Linux projects generally offer higher rates
• Project variety: Can handle infrastructure projects too
• Remote work: Server management location-independent
• Recurring projects: Long-term contracts for operations/maintenance

Target projects:

• Server construction and operations
• Cloud migration projects
• Docker/Kubernetes projects
• System monitoring and automation

No, it's a virtual environment running in your browser.

Features:

• Virtual file system implemented in JavaScript
• Faithfully simulates major Linux commands
• Safe environment with no impact on actual systems
• Specialized for learning-necessary features

While different from actual Linux, it provides sufficient functionality for learning.

We support these major commands:

• Navigation: pwd, ls, cd
• File operations: touch, cp, mv, rm, mkdir, rmdir
• Text processing: cat, echo, head, tail, grep
• System info: whoami, date, clear
• Permission management: chmod, chown (simulated)
• Others: find, sort, wc, etc.

We plan to expand supported commands in the future.

All files are temporarily saved in browser memory:

• Retained during session
• Returns to initial state on page reload
• Not saved to actual computer
• Not accessible to other users

Only learning progress is saved in localStorage and persists.

Internet connection required only for first access:

• Application download
• Learning content retrieval

After initial load, partially usable offline via browser cache, but internet connection recommended for latest features and content.

Error displayed when lacking access permissions:

• Cause: Lacking appropriate permissions for file/directory
• Symptoms: Cannot read, write, or execute file

Solutions:

• Check permissions: ls -l to check file permissions
• Change permissions: chmod 755 filename to grant execute permission
• Check owner: ls -l to verify owner
• Admin privileges: Use sudo command (real environment)

Error when specified file or directory not found:

• Wrong filename: Check spelling, case
• Wrong path: Verify current location and specified path
• Verify existence: Use ls to check existence

Verification steps:

1. pwd to check current location
2. ls to display file list
3. ls -la to check including hidden files
4. Try specifying with absolute path

Error when entered command not recognized by system:

• Wrong command name: Spelling mistakes or typos
• Command not installed: Command doesn't exist on system
• PATH settings: Executable path not set

Solutions:

• Check spelling: Enter command name accurately
• which command: which ls to verify path
• type command: type ls to check command type
• Check installation: Verify with package manager

When rm command can't delete files:

• Insufficient permissions: No deletion permission for file/directory
• File in use: Process using the file
• Read-only: File has read-only attribute

Resolution steps:

1. ls -l to check permissions
2. chmod +w filename to grant write permission
3. lsof filename to check process using file
4. rm -f filename for forced deletion (use carefully)

Occurs due to character encoding issues:

• Cause: Character code mismatch between system and file
• Symptoms: Filenames show as "?" or strange characters

Solutions:

• Check encoding: locale to verify system settings
• UTF-8 settings: export LANG=ja_JP.UTF-8
• Change filename: Recommend using alphanumeric filenames

This service recommends using alphanumeric filenames.

To stop running commands:

• Ctrl+C: Force terminate running command
• Ctrl+Z: Pause command (move to background)
• Ctrl+D: Send EOF (End of File)

Situation-specific responses:

• Infinite loop: Ctrl+C to force terminate
• Waiting for input: Ctrl+D to end input
• Long processing: Ctrl+Z to pause, then bg for background execution

Recovery methods when screen display is corrupted:

• reset command: reset to initialize terminal
• clear command: clear to clear screen
• stty command: stty sane to reset settings

In this service:

• Click "Clear" button
• Reload page (F5)
• Clear browser cache

Response when important files mistakenly deleted:

• Real environment response:
• Immediately stop work
• Use data recovery tools (testdisk, photorec)
• Restore from backups
• Prevention:
• rm -i for confirmation before deletion
• ls to verify files beforehand
• Regular backups of important files

In this service: Safe - page reload returns to initial state.

Please check the following:

1. Focus on input field: Click terminal input area
2. JavaScript enabled: Verify JavaScript enabled in browser settings
3. Reload page: F5 key or browser refresh button
4. Change browser: Try accessing with another browser

Possible causes:

• Private mode: Please use normal mode
• localStorage disabled: Check browser settings
• Storage capacity shortage: Organize browser data
• Cookie settings: Verify necessary cookies are allowed

We recommend using the same device and browser.

Please try the following:

1. Clear browser cache: Ctrl+F5 (hard refresh)
2. Check zoom settings: Set to 100% display
3. Update browser: Update to latest version
4. Disable extensions: Temporarily disable ad blockers, etc.

On mobile devices, portrait orientation is recommended.

Please verify the following:

• Check spelling: No mistakes in command names or arguments
• Case sensitivity: Linux distinguishes uppercase/lowercase
• Check spaces: No extra spaces
• Reconfirm lesson: Correctly understand required operations

Please also use the hint feature.

Method to reset learning records:

1. Click "📊 Dashboard" in header
2. Scroll to bottom of Dashboard page
3. Click "🔄 Reset Learning Records" button in "⚙️ Learning Data Management" section
4. Select "OK" in confirmation dialog

Warning: This operation cannot be undone. All progress and badges will be deleted.

Currently, cross-device progress sharing is not supported.

Progress is managed individually on each device's browser.

When we implement account features in the future, we plan to provide cross-device sync functionality.