IntroToLinux

3. Creating and Managing Users

Adding Users:

adduser (Interactive - Debian/Ubuntu)

# Interactive user creation (recommended for desktop)
sudo adduser newuser

# This prompts for:
# - Password
# - Full name
# - Room number
# - Work phone
# - Home phone
# - Other information

useradd (Command-line - Universal)

# Basic user creation
sudo useradd newuser

# Create user with home directory
sudo useradd -m newuser

# Create user with specific shell
sudo useradd -m -s /bin/bash newuser

# Create user with specific UID and GID
sudo useradd -m -u 1500 -g users newuser

# Create user with multiple groups
sudo useradd -m -G sudo,adm,plugdev newuser

# Create system user (no home directory)
sudo useradd -r systemuser

# Create user with expiration date
sudo useradd -m -e 2024-12-31 tempuser

Common useradd Options:

• -m: Create home directory
• -s shell: Set default shell
• -g group: Set primary group
• -G groups: Set secondary groups
• -u UID: Set specific UID
• -c comment: Set GECOS field (full name)
• -e date: Set expiration date
• -r: Create system account

Setting Passwords:

# Set password for user
sudo passwd username

# Set password for current user
passwd

# Force password change on next login
sudo passwd -e username

# Lock user account
sudo passwd -l username

# Unlock user account
sudo passwd -u username

# Check password status
sudo passwd -S username

Modifying Users:

usermod Command:

# Change username
sudo usermod -l newname oldname

# Change user's primary group
sudo usermod -g newgroup username

# Add user to secondary groups (append)
sudo usermod -aG sudo,adm username

# Replace user's secondary groups
sudo usermod -G sudo,adm username

# Change user's home directory
sudo usermod -d /new/home -m username

# Change user's shell
sudo usermod -s /bin/zsh username

# Lock user account
sudo usermod -L username

# Unlock user account
sudo usermod -U username

# Set account expiration
sudo usermod -e 2024-12-31 username

chsh: Change Shell

# Change current user's shell
chsh

# Change another user's shell
sudo chsh -s /bin/zsh username

# List available shells
cat /etc/shells

chfn: Change Full Name (GECOS)

# Change current user's information
chfn

# Change specific user's information
sudo chfn username

Deleting Users:

# Delete user but keep home directory
sudo userdel username

# Delete user and home directory
sudo userdel -r username

# Delete user and all files owned by user
sudo userdel -r -f username

# Alternative (Debian/Ubuntu)
sudo deluser username
sudo deluser --remove-home username

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Lesson Home: ↑ Lesson 9: Users & Groups Course Home: ⌂ Introduction to Linux