USER INFORMATION AND MANAGEMENT
# Display the user and group ids of your current user.
id
# Display the last users who have logged onto the system.
last
# Show who is logged into the system.
who
# Show who is logged in and what they are doing.
w
# Create a group named "test".
groupadd test
# Create an account named john, with a comment of "John Smith" and create the user's home directory.
useradd -c "John Smith" -m john
# Delete the john account.
userdel john
# Add the john account to the sales group
usermod -aG sales john