First Move (11~18) - Code, Learn, Build
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First Move (11~18) - Code, Learn, Build

Structured, level-based technology learning paths from foundational exploration to industry mastery.

Learning Domains

  • Python Programming (Active)
  • Computer Science Core
  • Web Development
  • AI & Machine Learning

Platform Architecture

  • Level-Based Progression
  • Decoupled Content Schema
  • Modular Code Execution Engine
  • Curated Official Resources

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Readability & Accessibility First

← Linux Systems & Security|Level 1: Linux CLI & File System Security

2. POSIX File Permissions (chmod, chown) & SUID Security

Lesson 2 of 6
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POSIX File Permissions (chmod, chown) & SUID Security

Master Read (4), Write (2), Execute (1) octal bits, user/group ownership (chown), and identify dangerous SUID root permission bits.

POSIX Permission Matrix & Octal Notation

### POSIX Permission Representation Permissions apply to three scope tiers: **User (u)**, **Group (g)**, and **Others (o)**. | Permission | Symbol | Octal Value | File Effect | Directory Effect | | :--- | :--- | :--- | :--- | :--- | | Read | `r` | 4 | Read contents | List files (`ls`) | | Write | `w` | 2 | Modify file | Create/delete files | | Execute | `x` | 1 | Run binary | Traverse (`cd`) | `chmod 755 script.sh` grants Read/Write/Execute (`7`) to user, and Read/Execute (`5`) to group and others.
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