Create, delete, and modify local user accounts

9. Manage Users and Groups

📘Red Hat Certified System Administrator (RHCSA – EX200)

Managing local users is a core Linux skill, and the RHCSA exam tests your ability to handle accounts quickly and correctly. Local users are accounts that exist only on the system (not on a network like LDAP).

We’ll cover:

Understanding local user accounts
Creating user accounts
Deleting user accounts
Modifying user accounts
Exam tips and examples

1. Understanding Local User Accounts

In Linux, every user has:

Username – e.g., alice
User ID (UID) – a number, usually starting at 1000 for regular users
Primary group – usually a group with the same name as the username
Home directory – where the user’s files are stored, e.g., /home/alice
Shell – the command-line interface the user uses, e.g., /bin/bash

Key files to know:

/etc/passwd – stores user account info (username, UID, home directory, shell)
/etc/shadow – stores encrypted passwords and password settings
/etc/group – stores group information

IT example: A system administrator creates accounts for employees so they can log in, access resources, and have personal directories.

2. Creating User Accounts

Linux provides the useradd command for creating users.

Basic syntax:

useradd [options] username

Most common options:

Option	Purpose
`-m`	Create a home directory if it doesn’t exist
`-s`	Set default shell (e.g., `/bin/bash`)
`-d`	Specify custom home directory
`-c`	Add a comment (usually full name)
`-G`	Add user to additional groups

Example 1: Basic user

sudo useradd -m alice
sudo passwd alice

-m creates /home/alice
passwd sets the password for alice
The user can now log in

Example 2: User with custom shell and comment

sudo useradd -m -s /bin/bash -c "Alice, IT Support" alice
sudo passwd alice

IT example: Alice needs /bin/bash to run scripts for system maintenance.

Checking the user

id alice

Output shows:

uid=1001(alice) gid=1001(alice) groups=1001(alice)

Confirms UID, GID, and groups

3. Deleting User Accounts

To remove a user, use the userdel command.

Syntax:

sudo userdel [options] username

Options:

Option	Purpose
`-r`	Remove the user’s home directory and mail spool

Example 1: Delete user but keep home directory

sudo userdel alice

Alice’s account is gone, but /home/alice remains

Example 2: Delete user and home directory

sudo userdel -r alice

Deletes account and /home/alice completely
IT example: When an employee leaves the company, their files are also removed if necessary.

4. Modifying User Accounts

The usermod command lets you change an existing account.

Basic syntax:

sudo usermod [options] username

Common options:

Option	Purpose
`-l newname`	Change username
`-d /new/home -m`	Move home directory
`-s /new/shell`	Change login shell
`-G group1,group2`	Add user to supplementary groups

Example 1: Change username

sudo usermod -l bob alice

Alice is now bob, but her home directory stays /home/alice unless you also move it

Example 2: Change home directory and move files

sudo usermod -d /home/bob -m bob

Moves files from old home directory to new one

Example 3: Add user to groups

sudo usermod -aG wheel,sudo bob

Adds bob to wheel and sudo groups
-aG is important; without -a, you replace all existing groups

5. Exam Tips

Always create a home directory for new users: -m
Use passwd to set passwords after creating accounts
Check users with id username or getent passwd username
Deleting a user with -r removes all their data — important for cleanup
To modify groups, use usermod -aG group username to avoid removing existing groups
RHCSA may ask you to create users, modify their shell/home, and delete them

6. Quick Commands Summary

Task	Command Example
Create user with home	`sudo useradd -m alice`
Set password	`sudo passwd alice`
Delete user	`sudo userdel alice`
Delete user with home	`sudo userdel -r alice`
Modify username	`sudo usermod -l bob alice`
Change home directory	`sudo usermod -d /home/bob -m bob`
Add user to group	`sudo usermod -aG wheel,sudo bob`
Check user info	`id bob`

✅ Key points for the RHCSA exam:

Know useradd, usermod, userdel, passwd
Understand home directories, shells, and groups
Practice creating, deleting, and modifying users quickly