How to Add and Manage Users on Linux

Creating Users

# Create a new user with home directory
sudo adduser john

# Create a system user (no home, no login shell)
sudo useradd --system --no-create-home --shell /usr/sbin/nologin appuser

Managing Passwords

# Set or change a password
sudo passwd john

# Force password change on next login
sudo passwd --expire john

# Lock an account
sudo passwd --lock john

# Unlock an account
sudo passwd --unlock john

Groups

# Create a group
sudo groupadd developers

# Add user to a group
sudo usermod -aG developers john

# View user groups
groups john
id john

# Remove user from a group
sudo gpasswd -d john developers

Sudo Access

# Add user to sudo group
sudo usermod -aG sudo john    # Debian/Ubuntu
sudo usermod -aG wheel john   # RHEL/Rocky

# Or use visudo for custom permissions
sudo visudo
# Add: john ALL=(ALL) NOPASSWD: /usr/bin/systemctl restart nginx

Deleting Users

# Delete user (keep home directory)
sudo userdel john

# Delete user and home directory
sudo userdel --remove john

Viewing User Info

# List all users
cat /etc/passwd

# Currently logged in users
who
w

# Last login history
last john
lastlog

Security Best Practices

• Disable the root login over SSH
• Use SSH keys instead of passwords
• Create individual accounts for each person (no shared accounts)
• Remove accounts for people who no longer need access
• Use the principle of least privilege for sudo access