Linux chmod and chown Guide

Complete beginner-friendly guide to chmod and chown on Linux, covering Arch Linux, CachyOS, and other distributions including file permissions, ownership, and access control.

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Table of Contents

1. Understanding Permissions
2. chmod Usage
3. chown Usage
4. Permission Examples
5. Troubleshooting

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Understanding Permissions

File Permissions

Three permission types:

• Read (r): View file contents
• Write (w): Modify file
• Execute (x): Run file as program

Three permission groups:

• Owner: File owner
• Group: File group
• Others: Everyone else

Permission Numbers

Numeric values:

• 4: Read
• 2: Write
• 1: Execute
• 7: Read + Write + Execute (4+2+1)
• 6: Read + Write (4+2)
• 5: Read + Execute (4+1)

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chmod Usage

Change Permissions

Basic syntax:

# Change permissions
chmod permissions file

# Numeric mode
chmod 755 file.txt

# Symbolic mode
chmod u+x file.txt

Numeric Mode

Set permissions:

# Owner: read+write+execute, Group: read+execute, Others: read+execute
chmod 755 file.txt

# Owner: read+write, Group: read, Others: read
chmod 644 file.txt

# Owner: read+write+execute, Group: none, Others: none
chmod 700 file.txt

Symbolic Mode

Modify permissions:

# Add execute for owner
chmod u+x file.txt

# Remove write for group
chmod g-w file.txt

# Add read for others
chmod o+r file.txt

# Set all permissions
chmod a=rwx file.txt

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chown Usage

Change Ownership

Basic syntax:

# Change owner
chown user file.txt

# Change owner and group
chown user:group file.txt

# Recursive
chown -R user:group directory/

Examples

Common uses:

# Change owner
sudo chown username file.txt

# Change owner and group
sudo chown username:groupname file.txt

# Change recursively
sudo chown -R username:groupname directory/

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Permission Examples

Common Permissions

File permissions:

# Executable script
chmod 755 script.sh

# Configuration file
chmod 644 config.conf

# Private file
chmod 600 private.txt

# Directory
chmod 755 directory/

Directory Permissions

Directory needs:

• Read: List directory contents
• Write: Create/delete files
• Execute: Enter directory

# Standard directory
chmod 755 directory/

# Private directory
chmod 700 directory/

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Troubleshooting

Permission Denied

Fix permissions:

# Check current permissions
ls -l file.txt

# Add execute permission
chmod +x file.txt

# Or use sudo
sudo chmod 755 file.txt

Ownership Issues

Fix ownership:

# Check ownership
ls -l file.txt

# Change owner
sudo chown username file.txt

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Summary

This guide covered chmod and chown usage, file permissions, and ownership for Arch Linux, CachyOS, and other distributions.

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Next Steps

• User and Groups - User management
• System Configuration - System setup
• chmod Documentation: man chmod
• chown Documentation: man chown

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This guide covers Arch Linux, CachyOS, and other Linux distributions. For distribution-specific details, refer to your distribution's documentation.