Linux su Guide

Linux su Guide

Complete beginner-friendly guide to su on Linux, covering Arch Linux, CachyOS, and other distributions including switching users, becoming root, and user switching.

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Table of Contents

1. Understanding su
2. su Basics
3. Switching Users
4. su vs sudo
5. Troubleshooting

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Understanding su

What is su?

su (switch user) changes to another user account.

Uses:

• Switch users: Change to different user
• Become root: Switch to root account
• Test permissions: Test as different user
• System maintenance: Run commands as root

Note: Prefer sudo for security, but su is still useful.

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su Basics

Become Root

Switch to root:

# Switch to root
su

# Enter root password
# Now you're root

# Exit
exit

Switch to User

Change user:

# Switch to user
su username

# Enter user password
# Now you're that user

# Exit
exit

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Switching Users

With Environment

Preserve environment:

# Switch with current environment
su - username

# Or
su -l username

# Full login shell

Without Environment

Minimal environment:

# Switch without changing environment
su username

# Uses current environment

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su vs sudo

When to Use su

Use su when:

• Need root shell: Extended root session
• System maintenance: Multiple root commands
• Testing: Test as different user

When to Use sudo

Use sudo when:

• Single command: One command as root
• Security: Better audit trail
• Best practice: Recommended approach

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Troubleshooting

Authentication Failed

Check password:

# Verify user exists
id username

# Check if user has password
sudo passwd username

# Try again
su username

Permission Denied

Check access:

# Verify user in wheel group
groups username

# Check /etc/group
grep wheel /etc/group

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Summary

This guide covered su usage, user switching, and when to use su vs sudo for Arch Linux, CachyOS, and other distributions.

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Next Steps

• sudo Guide - sudo usage
• User and Groups - User management
• su Documentation: man su

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