The document provides a complete guide to using the "useradd" command in Linux to add new user accounts. It covers the basic syntax of the useradd command and various options such as -m to create a home directory, -u to specify a user ID, -g to assign a primary group, and -G to assign secondary groups. The document also discusses how to set expiration dates, comments, login shells, and passwords for new users. Examples are given for each configuration.

1. A Complete Guide to “useradd” Command in
Linux with Examples | Hostbillo
Introduction
Multiple users can interact with Linux at once because it is a multi-user system.
You are accountable for overseeing the system's users and groups by allowing
and denying users and adding and removing them from different groups.
This article will cover how to use the useradd command in Linux to set up
new user accounts.
Useadd Command
For the useradd command in Linux, the following general syntax applies:
useradd [OPTIONS] USERNAME

2. Users with sudo benefits or root are the only ones who can create new user
accounts in Linux using the useradd command.
According to the choices you type at the command prompt, the useradd
command creates a new user account once you run it.
Since the variables in this file are different between distributions, the Linux add
user command behaves differently on various systems.
Additionally, useradd reads the data in the /etc/login.defs file. This file includes
configuration information for the shadow password suite, including password
expiration policy, user ID ranges used when creating the system and regular
users, and more.
How to add User in Linux?
Use the useradd command after entering the user's name to create a new user
in Linux.
If you wanted to make a new user with the name username, you might run:
sudo username

3. Useradd uses the default settings listed in the /etc/default/useradd file when it is
run without any options, creating a new user account.
You need to mark the account password prior to logging into the recently
created user in linux. Perform the passwd comm and, then enter the username:
sudo passwd username.
Keep in mind to choose an unique password.
Add a New User and Create a Home Directory
Most Linux distributions do not build the user's home directory whenever a
newly added account is set up with useradd command.
The home directory would be created by implementing the -m (—create-home)
element.

4. sudo useradd -m username
With the aforementioned command, the user's home directory is created and
files from the /etc/skel directory are copied over. You can find the initialization
files by listing the files in the /home/username directory:
ls -la /home/username/
A user's home directory can contain folders and files that they can add, change,
and delete.
Create a User with Specific Home Directory
Useradd Command in Linux instantly creates the home directory. If you want to
place the user's home directory somewhere else, then use d (—home) feature.
Using the example below, you can make a new user with the name username
and a home directory of /opt/username:

5. sudo useradd -m -d /opt/username username
Create New User in Linux with Specific User Id
Usernames and unique UIDs are used in Linux and other Unix-like operating
systems to identify users.
The Linux program gives each user a special positive integer that they can refer
to as their "user identifier" (UID). The UID as well as other access control
policies define the types of activities a user is allowed to perform on system
resources.
The system will automatically designate the following UID from the catalog of
user IDs mentioned in the login.defs file to a newly created user Linux.
When operating useradd, utilise -u (—uid) option to set up a user with an unique
UID. For instance, to create a new user with the UID of 1700 and the name
username, you would type:
sudo useradd -u 1700 username
With the id command, you can confirm the user's UID:
id -u username

6. Create a User with a Specific Group Id
User accounts in Linux are organized and managed by groups, which are
organizational units. The main function of groups is to specify a set of privileges
that can be shared by all members of the group, such as permissions for reading,
writing, or implementing a specific resource.
When adding a new user, the useradd prompt automatically creates a group that
has the exact name as the username and the identical GID as the UID.
By using -g (—gid) feature, you can allocate a user to a specific initial login
group. You can choose between stating the group name and the GID number.
The group ID or name must already be in use.
In this example, we'll create a brand-new user with the name username, and
we'll set the login group to user type.
sudo useradd -g users username
You could perhaps validate the user's GID by using id prompt:
id -gn username

7. Add a User and allot Multiple Groups
The terms "primary group" as well as "secondary group" refer to two distinct
categories in Linux operating systems. Each user has a maximum of one
primary group and zero to more secondary groups to which they can belong.
With the -G (—groups) option, you can specify a list of extra groups that the
user will belong to.
With the primary group users, secondary groups wheel, and docker, the
following command creates a new user with the name username.
sudo useradd -g users -G wheel
Additionally, you could incorporate searching
id username
Add User in Linux without any Home Directory
Some situations call for us to step away from giving users home directories for
safety purposes. In this case, the user's home directory will be root when they
log into a system that has just restarted. When such a user executes the su
command, the previous user's home directory will be used as the login directory.
Using the option "-M," users can be created without having home directories.
You can make a user without the need for a home directory by using the
command prompt, for example.

8. sudo useradd -M username
The ls command will now be used to confirm that the user was established with
no need for a home directory.
sudo ls -l /home/username
ls: cannot access /home/username: No such file or directory
Add New User with Expiry Date
You can designate a day and time for the newly added accounts' expiration by
using the -e (—expiredate) feature. This can be used to create temporary
accounts.
In order to specify a date, use the format YYYY-MM-DD.
For instance, to make a new user account with the name username (ABC) and
an expiration date of April 07th, 2023, you would execute the following
command:
sudo useradd -e 2023-04-07 username (ABC)
To find out when an account will expire, choose the chage prompt:
sudo chage -l username(ABC)

9. Create New User with Custom Comments
You can provide a precise description for the new user by using the -c
(—comment) option. Usually, a comment will include the user's full name or
contact information.
In the example below, we are adding a new user with the name username and
the comment text string Test User Account:
sudo useradd -c "Test User Account" username
grep username /etc/passwd
Another name for the comment section is GECOS.
Add User with a changed login shell

10. The login shell for a new user is automatically set to the one listed in the
/etc/default/useradd file. The default shell setting varies between distributions;
in some, it is /bin/sh, and in others, /bin/bash.
With the -s (—shell) feature, you can identify the newly added user's login shell.
For example,
sudo useradd -s /usr/bin/zsh username
Determine the user's login shell by examining the entry in the file:
grep username /etc/passwd
The command for Changing the Default useradd Values
The -D, —defaults function, allows you to see and modify the standard useradd
configurations.
To see the current default options, use the following syntax:
useradd -D
Consider the scenario where you want to switch from /bin/sh to /bin/bash as the
default login shell. Enter the new shell in the following format to achieve that:
sudo useradd -D -s /bin/bash

11. Users can actually confirm that the standard shell component has been altered
by running the command shown below:
sudo useradd -D | grep -i shell
Command to set a Password for New User
The following command can be used to set an unencrypted password for the
user.
sudo useradd -p test_password username
This will set up a new user with the name "username" and the unencrypted
password "test password".
Command to Display Help
You can demonstrate help by entering the following syntax.
sudo useradd --help
The useradd command's help section will be displayed when this command is
used.

12. Conclusion
We've demonstrated in this article how to use the useradd command in Linux
to add new user accounts. All Linux distributions, such as CentOS, RHEL,
Debian, Ubuntu, and others, also should follow the same instructions. As of
right now, you can test these features and attempt to give Lunix more
functionality.