Adding and managing Users in Linux
Adding a new user involves dealing with an account other than your own which requires superuser (aka root) privileges. The same applies to other user or group management tasks, such as deleting an account, updating accounts, and creating and removing groups.
These operations are performed using the following commands:
adduser: add a user to the system.
userdel: delete a user account and related files.
addgroup: add a group to the system.
delgroup: remove a group from the system.
usermod: modify a user account.
chage: change user password expiry information.
sudo: run one or more commands as another user (typically with superuser permissions).
Relevant files: /etc/passwd (user information), /etc/shadow (encrypted passwords), /etc/group (group information) and /etc/sudoers (configuration for sudo).