Ubuntu Users and Groups

Add a new user

# Add a user
sudo useradd user1

# Add a user AND create HOME (/home/user1) directory
sudo useradd --create-home user1 

# Add a password for user 1
sudo passwd user1

# Add user Interactively 
sudo adduser user2

Manage Groups

# Add or Delete Groups
sudo addgroup groupname
sudo delgroup groupname

# Add user to a group
sudo usermod -a -G groupname user1

# list groups
getent group
less /etc/group

# All groups of a User
groups user1
id user1

# All users of a group
getent group sudo