# 1. Create test users
sudo useradd -m -s /bin/bash alice
sudo useradd -m -s /bin/bash bob
sudo useradd -m -s /bin/bash charlie
# 2. Set passwords
sudo passwd alice
sudo passwd bob
sudo passwd charlie
# 3. Check user information
id alice
getent passwd alice
groups alice
# 4. Modify user properties
sudo usermod -c "Alice Johnson" alice
sudo usermod -aG sudo bob
# 5. Verify changes
getent passwd alice
groups bob
# 1. Create project groups
sudo groupadd developers
sudo groupadd testers
sudo groupadd project-alpha
# 2. Add users to groups
sudo usermod -aG developers alice
sudo usermod -aG developers bob
sudo usermod -aG testers charlie
sudo usermod -aG project-alpha alice
sudo usermod -aG project-alpha charlie
# 3. Verify group membership
groups alice
groups bob
groups charlie
getent group developers
# 1. Check current sudo privileges
sudo -l
# 2. Add user to sudo group
sudo usermod -aG sudo alice
# 3. Test sudo access
sudo -u alice sudo whoami
# 4. Create custom sudo rule
sudo visudo
# Add line: charlie ALL=(ALL) NOPASSWD: /usr/bin/systemctl status *
# 5. Test custom rule
sudo -u charlie sudo systemctl status ssh
# 1. Check users with shells
grep "/bin/bash\|/bin/sh" /etc/passwd
# 2. Find users with UID 0 (should only be root)
awk -F: '$3 == 0 {print $1}' /etc/passwd
# 3. Check for empty passwords
sudo awk -F: '$2 == "" {print $1}' /etc/shadow
# 4. Check sudo group members
getent group sudo
# 5. Check recent logins
last | head -10
# 6. Check failed login attempts
sudo grep "Failed password" /var/log/auth.log | tail -10
Next: → User Security Best Practices
Previous: ← User Environment And Configuration
Lesson Home: ↑ Lesson 9: Users & Groups
Course Home: ⌂ Introduction to Linux