User Management

1. Overview

User management includes everything from creating a user to deleting a user on your system. User management can be done in three ways on a Linux system.

2. Description

2.1 Local user database

/etc/passwd  

It has seven columns separated by a colon

demyank:x:1000:1000:demyank:/home/demyank:/bin/bash
username, an x, user id, primary group id, a description, name of home directory and a login shell

2.2 Group database

/etc/group  

2.3 root

The root user is the superuser and have all the powers for creating a user, deleting a user and can even login with the other user's account. The root user always has userid 0

2.3.1 Switch to root account

[demyank@localhost ~]$ su
Password: 

2.3.2 Adding a user to superuser

usermod -aG wheel demyank

2.3.3 Enable wheel group to use sudo

visudo: Edit /etc/sudoers

Uncomment below line

# %wheel	ALL=(ALL)	ALL

2.4 Managing User and Group

2.4.1 useradd

[demyank@localhost ~]$ adduser testuser

2.4.2 Switching to a specific user

[demyank@localhost ~]$ su - testuser
[testuser@localhost ~]$

2.4.3 list groups

[testuser@localhost ~]$ groups
testuser

2.4.4 usermod

[root@localhost ~]$ usermod -aG wheel testuser

2.4.5 userdel

[root@localhost ~]$ userdel testuser
# By using userdel -r option, you can delete home directory along with user account.
[root@localhost ~]$ userdel -r testuser 

 

3. Reference

https://linuxhint.com/sudo_linux/

https://www.javatpoint.com/linux-user-management

https://www.rosehosting.com/blog/how-to-create-users-and-manage-their-sudo-privileges-on-ubuntu/

https://www.tecmint.com/fix-user-is-not-in-the-sudoers-file-the-incident-will-be-reported-ubuntu/

https://unix.stackexchange.com/questions/370400/cant-add-user-to-sudo-group-in-centos-7-i386no-gui-its-minimal