Linux Users and Sudo
Introduction
Before we proceed, it would be best to cover some basic user administration topics that will be very useful in later chapters. Adding Users
One of the most important activities in administering a Linux box is the addition of users. Here you’ll find some simple examples to provide a foundation for future chapters. It is not intended to be comprehensive, but is a good memory refresher. You can use the command man useradd to get the help pages on adding users with the useradd command or the man usermod to become more familiar with modifying users with the usermod command.
Who Is the Super User?
The super user with unrestricted access to all system resources and files in Linux is the user named root. This user has a user ID, of 0 which is universally identified by Linux applications as belonging to a user with supreme privileges. You will need to log in as user root to add new users to your Linux server.
Debian Note: When installing Ubuntu Linux systems, you are prompted to create a primary user that is not root. A root user is created but no password is set, so you initially cannot log in as this user. The primary user can become the root user using the sudo su - command that will be discussed later.
How To Add Users
Adding users takes some planning; read through these steps below before starting:
1) Arrange your list of users into groups by function. In this example there are three groups « parents« , « children » and « soho« .
Parents Children Soho Paul Alice Accounts Jane Derek Sales
2) Add the Linux groups to your server:
[root@bigboy tmp]# groupadd parents [root@bigboy tmp]# groupadd children [root@bigboy tmp]# groupadd soho
3) Add the Linux users and assign them to their respective groups
[root@bigboy tmp]# useradd -g parents paul [root@bigboy tmp]# useradd -g parents jane [root@bigboy tmp]# useradd -g children derek [root@bigboy tmp]# useradd -g children alice [root@bigboy tmp]# useradd -g soho accounts [root@bigboy tmp]# useradd -g soho sales
If you don’t specify the group with the -g, RedHat/Fedora Linux creates a group with the same name as the user you just created; this is also known as the User Private Group Scheme. When each new user first logs in, they are prompted for their new permanent password.
4) Each user’s personal directory is placed in the /home directory. The directory name will be the same as their user name.
[root@bigboy tmp]# ll /home drwxr-xr-x 2 root root 12288 Jul 24 20:04 lost found drwx------ 2 accounts soho 1024 Jul 24 20:33 accounts drwx------ 2 alice children 1024 Jul 24 20:33 alice drwx------ 2 derek children 1024 Jul 24 20:33 derek drwx------ 2 jane parents 1024 Jul 24 20:33 jane drwx------ 2 paul parents 1024 Jul 24 20:33 paul drwx------ 2 sales soho 1024 Jul 24 20:33 sales [root@bigboy tmp]#
