How do you manage users and groups in Linux?

# User management
useradd username         # Add new user
useradd -m -s /bin/bash username  # Create with home directory
userdel username         # Delete user
userdel -r username      # Delete user and home directory
usermod -aG groupname username    # Add user to group
passwd username          # Change user password
chage -l username        # View password aging info
# Group management
groupadd groupname       # Create new group
groupdel groupname       # Delete group
gpasswd -a username groupname     # Add user to group
gpasswd -d username groupname     # Remove user from group
# View user/group information
id username              # Show user ID and groups
groups username          # Show user's groups
getent passwd username   # Get user info from database
getent group groupname   # Get group info