Cheatsheet: Other Operating Systems

1. Linux Overview

1.1 Key Characteristics

• Open-source, Unix-like operating system kernel developed by Linus Torvalds (1991)
• Free to use, modify, and distribute under GPL (General Public License)
• Case-sensitive file system and commands
• Multiuser, multitasking architecture
• Strong security model with user permissions and groups
• Kernel-based architecture with modular design

1.2 Common Distributions

2. Linux File System Structure

2.1 Directory Hierarchy

2.2 File System Types

• ext4: Most common Linux file system, journaling, supports volumes up to 1 EB
• ext3: Older journaling file system, predecessor to ext4
• XFS: High-performance 64-bit journaling file system
• Btrfs: Copy-on-write file system with snapshot and RAID support
• NTFS: Supported via ntfs-3g driver for Windows compatibility
• FAT32/exFAT: Supported for removable media compatibility

3. Linux Basic Commands

3.1 File and Directory Operations

3.2 File Permissions

3.2.1 Permission Values

• Read (r) = 4, Write (w) = 2, Execute (x) = 1
• Three groups: Owner, Group, Others
• Example: 755 = rwxr-xr-x (owner full, group/others read+execute)
• Example: 644 = rw-r--r-- (owner read+write, group/others read only)

3.3 System Information

3.4 Process Management

3.5 Package Management

3.6 User Management

3.7 Network Commands

4. Linux Shell and Scripting

4.1 Shell Types

• Bash (Bourne Again Shell): Default shell on most Linux distributions
• sh (Bourne Shell): Original Unix shell
• csh/tcsh (C Shell): C-like syntax
• zsh (Z Shell): Extended Bash with additional features

4.2 Shell Basics

4.3 Common Bash Script Elements

• Shebang: #!/bin/bash (first line of script)
• Variables: VAR="value" (no spaces around =)
• Comments: # comment text
• Execute permission required: chmod +x script.sh
• Run script: ./script.sh or bash script.sh

5. macOS Overview

5.1 Key Characteristics

• Unix-based operating system developed by Apple Inc.
• Built on Darwin foundation (BSD Unix derivative)
• Proprietary OS for Macintosh computers
• GUI-focused with command-line interface available via Terminal
• File system: APFS (Apple File System) since macOS High Sierra
• Case-insensitive by default, case-preserving file system

5.2 System Architecture

5.3 File System Structure

6. macOS Tools and Features

6.1 System Utilities

6.2 Finder Features

• Spotlight: System-wide search (Cmd+Space)
• Quick Look: Preview files without opening (Space bar)
• Tags: Color-coded labels for file organization
• AirDrop: Wireless file sharing between Apple devices
• iCloud Drive: Cloud storage integration
• Smart Folders: Saved searches

6.3 Common macOS Terminal Commands

6.4 Package Management

6.5 Security Features

• Gatekeeper: Controls which applications can be installed and run
• FileVault: Full disk encryption
• XProtect: Built-in malware detection
• System Integrity Protection (SIP): Protects system files from modification
• Firewall: Application-based firewall control
• Touch ID/Face ID: Biometric authentication (hardware dependent)

7. Chrome OS

7.1 Key Characteristics

• Linux-based operating system developed by Google
• Built on Gentoo Linux foundation with Chrome browser as primary interface
• Cloud-centric, designed for web applications
• Automatic updates and security patches
• Fast boot times (typically under 10 seconds)
• Primarily for Chromebook devices
• Supports Android apps via Google Play Store
• Linux application support via Crostini container

7.2 Architecture

7.3 File Management

• Files app: Built-in file manager
• Downloads folder: Local storage location
• Google Drive integration: Primary cloud storage
• Limited local storage (emphasizes cloud storage)
• Support for external drives and SD cards
• File types: .crx for Chrome extensions

7.4 Key Features

7.5 Common Crosh Commands

7.6 System Updates

• Automatic updates in background
• A/B partition system for seamless updates
• Updates applied after reboot
• No user intervention required
• Check for updates: Settings > About Chrome OS > Check for updates

8. Cross-Platform Comparisons

8.1 File System Comparison

8.2 Command Line Comparison

8.3 User Interface Elements

9. Troubleshooting and Maintenance

9.1 Linux Troubleshooting

9.2 macOS Troubleshooting

9.3 Chrome OS Troubleshooting

9.4 Recovery and Reset Options