How to create a linux user with(out) root privilege

Introduction

Laymen explanation

root is the user name or account that by default has access to all commands andfiles on a Linux or other Unix-like operating system. It is also referred to as theroot account, root user and the superuser.

Technical explanation

Root privileges are the powers that the root account has on the system. The root account is the most privileged on the system and has absolute power over it (i.e., complete access to all files and commands). Among root's powers are the ability to modify the system in any way desired and to grant and revoke access permissions (i.e., the ability to read, modify and execute specific files and directories) for other users, including any of those that are by default reserved for root.

Every user account is automatically assigned an identification number, the UID(i.e., user ID), The UID for root (as well as for all other users) can be seen by looking at/etc/passwd, which is the configuration file for user data. This file can be viewed (by default by all users) by using the cat command (which is commonly employed to read files), i.e.,

cat /etc/passwd | less

The line of output for root will look something like root:x:0:0:root:/root:/bin/bash.

The first column shows the user name and the third column shows the UID, which can be seen to be zero

Steps to create a new root user

Lets say we need to add a new user and grand him root privileges.

Use the following commands to create the new user newroot, grand him the same privileges as root and set him a password :

# useradd -ms -ou 0 -g 0 newroot

# passwd newroot

We've just created the user newroot, with UID 0 and GID 0, so he is in the same group and has the same permissions as root.

Steps to create non-root user

Add a nonroot user

root@a8190999f141:/# adduser nonroot

Adding user `nonroot' ...

Adding new group `nonroot' (1000) ...

Adding new user `nonroot' (1000) with group `nonroot' ...

Creating home directory `/home/nonroot' ...

Copying files from `/etc/skel' ...

Enter new UNIX password:

Retype new UNIX password:

passwd: password updated successfully

Changing the user information for nonroot

Enter the new value, or press ENTER for the default

Full Name []: nonroot

Room Number []:

Work Phone []:

Home Phone []:

Other []:

Is the information correct? [Y/n] y

root@a8190999f141:/#

You can also add this user to sudoer list using following command

$ usermod -aG sudo username

Step to list all users with root privilege

Those who are root have "0" as the user id. So, below command will list all users having root privilege

grep 'x:0:' /etc/passwd

Reference

http://www.shellhacks.com/en/HowTo-Create-USER-with-ROOT-Privileges-in-Linux

http://www.linfo.org/root.html

http://serverfault.com/questions/208347/how-do-i-list-all-users-with-root

https://www.tecmint.com/add-users-in-linux/

https://www.digitalocean.com/community/tutorials/how-to-create-a-sudo-user-on-ubuntu-quickstart