sudo and su commands

Think of sudo and su like different ways to get special access. sudo is like having a temporary key card for specific tasks, while su is like changing your identity completely. Understanding when to use each command helps you work safely and efficiently.

Note: You do not have sudo access on the Cidermill server. However, it is still important to understand what sudo and su do.

Quick Reference

When to Use Each Command

• Use sudo when:
  • Running single admin commands
  • Installing software
  • Editing system files
  • Managing services
• Use su when:
  • Need extended root access
  • Working as another user
  • Multiple system changes
  • System maintenance tasks

Basic sudo Usage

Think of sudo like a temporary promotion - it gives you special powers just for the command you're running.

# Install software
sudo apt install package-name

# Edit system configuration
sudo nano /etc/config-file

# Restart a service
sudo systemctl restart service-name

# Check disk space
sudo df -h

# View system logs
sudo journalctl -xe

Understanding su (Switch User)

Think of su like changing your identity completely - it lets you switch to another user account, including the root user. While sudo gives temporary privileges, su actually changes your user context.

# Switch to root user
su
# Enter root password

# Switch to specific user
su username
# Enter user's password

# Switch to root with environment
su -

# Switch to user with environment
su - username

# Exit back to your original user
exit

Understanding sudo Options

# Start root shell
sudo -i

# Run command as another user
sudo -u username command

# See what you're allowed to do
sudo -l

# Extend sudo timeout
sudo -v

Tips for Success

• Always double-check commands before using sudo or su
• Use sudo for single commands when possible
• Use su only when you need extended access
• Read error messages carefully
• Keep root sessions as short as possible

Common Mistakes to Avoid

• Using sudo or su for everything
• Not reading error messages
• Leaving root shells open
• Using sudo with untrusted commands
• Forgetting to exit su sessions

Best Practices

• Use sudo instead of su when possible
• Keep root sessions brief
• Read error messages carefully
• Use specific commands instead of root shell
• Document sudo/su usage in scripts

Advanced Techniques

# Run multiple commands with one sudo
sudo sh -c 'command1 && command2'

# Use sudo in scripts
#!/bin/bash
if [ "$(id -u)" != "0" ]; then
    echo "This script must be run as root" 1>&2
    exit 1
fi

# Run commands as different users
sudo -u user1 command1
sudo -u user2 command2

# Use sudo with pipes
sudo cat /etc/passwd | grep username

Security Considerations

Think of sudo and su like powerful tools - they're useful but need to be handled carefully:

• Never share your sudo password or root password
• Be careful with sudo/su in scripts
• Check file permissions before editing
• Use specific commands instead of root shell
• Keep sudo timeout short

# Check file permissions before editing
ls -l /etc/config-file
sudo nano /etc/config-file

# Use specific commands instead of root shell
sudo apt update
sudo apt upgrade

# Set shorter sudo timeout
sudo visudo
# Add: Defaults timestamp_timeout=5