How To Create User On Centos

We all are aware of the most popular command called 'useradd' or 'adduser' in Linux. There are times when a Linux System Administrator is asked to create user accounts on Linux with some specific properties, limitations, or comments.

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In Linux, a 'useradd' command is a low-level utility that is used for adding/creating user accounts in Linux and other Unix-like operating systems. The 'adduser' is much similar to the useradd command because it is just a symbolic link to it.

add users in linux — useradd command examples

In some other Linux distributions, the useradd command may come with a slightly different version. I suggest you read your documentation, before using our instructions to create new user accounts in Linux.

When we run the 'useradd' command in the Linux terminal, it performs the following major things:

It edits /etc/passwd, /etc/shadow, /etc/group and /etc/gshadow files for the newly created user accounts.
Creates and populates a home directory for the new user.
Sets permissions and ownerships to the home directory.

Useradd Command Syntax

The Basic syntax of the useradd command is:

# useradd [options] username

In this article, we will show you the most used 15 useradd commands with their practical examples in Linux. We have divided the section into two parts from Basic to Advance usage of the command.

Part I: Basic Useradd Commands with 10 examples
Part II: Advance Useradd Commands with 5 examples

Part I – 10 Basic Usage of useradd Commands

1. How to Add a New User in Linux

To add/create a new user, you've to follow the command 'useradd' or 'adduser' with 'username'. The 'username' is a user login name, that is used by a user to login into the system.

Only one user can be added and that username must be unique (different from other usernames already exists on the system).

For example, to add a new user called 'tecmint', use the following command.

[[email protected] ~]# useradd tecmint

When we add a new user in Linux with the 'useradd' command it gets created in a locked state and to unlock that user account, we need to set a password for that account with the 'passwd' command.

[[email protected] ~]# passwd tecmint Changing password for user tecmint. New UNIX password: Retype new UNIX password: passwd: all authentication tokens updated successfully.

Once a new user is created, its entry is automatically added to the '/etc/passwd' file. The file is used to store the user's information and the entry should be.

tecmint:x:1000:1000:tecmint:/home/tecmint:/bin/bash

The above entry contains a set of seven colon-separated fields, each field has its own meaning. Let's see what are these fields:

Username: User login name used to login into the system. It should be between 1 to 32 characters long.
Password: User password (or x character) stored in /etc/shadow file in encrypted format.
User ID (UID): Every user must have a User ID (UID) User Identification Number. By default, UID 0 is reserved for the root user and UID's ranging from 1-99 are reserved for other predefined accounts. Further UID's ranging from 100-999 are reserved for system accounts and groups.
Group ID (GID): The primary Group ID (GID) Group Identification Number stored in the /etc/group file.
User Info: This field is optional and allows you to define extra information about the user. For example, user full name. This field is filled by the 'finger' command.
Home Directory: The absolute location of the user's home directory.
Shell: The absolute location of a user's shell i.e. /bin/bash.

2. Create a User with Different Home Directory

By default 'useradd' command creates a user's home directory under /home directory with a username. Thus, for example, we've seen above the default home directory for the user 'tecmint' is '/home/tecmint'.

However, this action can be changed by using the '-d' option along with the location of the new home directory (i.e. /data/projects). For example, the following command will create a user 'anusha' with a home directory '/data/projects'.

[[email protected] ~]# useradd -d /data/projects anusha [[email protected] ~]# passwd anusha

You can see the user home directory and other user-related information like user id, group id, shell, and comments.

[[email protected] ~]# cat /etc/passwd | grep anusha          anusha:x:1001:1001::/data/projects:/bin/bash

Create User with Home Directory in Linux

3. Create a User with a Specific User ID

In Linux, every user has its own UID (Unique Identification Number). By default, whenever we create a new user account in Linux, it assigns userid 500, 501, 502, and so on…

But, we can create users with custom userid with the '-u' option. For example, the following command will create a user 'navin' with custom userid '1002'.

[[email protected] ~]# useradd -u 1002 navin

Now, let's verify that the user created with a defined userid (1002) using the following command.

[[email protected] ~]# cat /etc/passwd | grep navin  navin:x:1002:1002::/home/navin:/bin/bash

Create User with User ID in Linux — Create User with the User ID in Linux

NOTE: Make sure the value of a user ID must be unique from any other already created users on the system.

4. Create a User with a Specific Group ID

Similarly, every user has their own GID (Group Identifier). We can create users with specific group IDs as well with the -g option.

Here in this example, we will add a user 'tarunika' with a specific UID and GID simultaneously with the help of '-u' and '-g' options.

[[email protected] ~]# useradd -u 1005 -g tecmint tarunika

Now, see the assigned user id and group id in '/etc/passwd' file.

[[email protected] ~]# cat /etc/passwd | grep tarunika          tarunika:x:1005:1000::/home/tarunika:/bin/bash

To verify the user's GID, use the id command:

[[email protected] ~]# id -gn tarunika

5. Add a User to Multiple Groups

The '-G' option is used to add a user to additional groups. Each group name is separated by a comma, with no intervening spaces.

Here in this example, we are adding a user 'tecmint' into multiple groups like admins, webadmin, and developer.

[[email protected]:~]# groupadd admins [[email protected]:~]# groupadd webadmin [[email protected]:~]# groupadd developers [[email protected]:~]# usermod -a -G admins,webadmin,developers tecmint [[email protected]:~]# useradd -G admins,webadmin,developers paddy

Next, verify that the multiple groups are assigned to the user with the id command.

[[email protected] ~]# id tecmint  uid=1000(tecmint) gid=1000(tecmint) groups=1000(tecmint),1007(admins),1008(webadmin),1009(developers) context=root:system_r:unconfined_t:SystemLow-SystemHigh

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6. Add a User without Home Directory

In some situations, where we don't want to assign home directories for a user, due to some security reasons. In such a situation, when a user logs into a system that has just restarted, its home directory will be root. When such a user uses the su command, its login directory will be the previous user's home directory.

To create users without their home directories, '-M' is used. For example, the following command will create a user 'shilpi' without a home directory.

[[email protected] ~]# useradd -M shilpi

Now, let's verify that the user is created without a home directory, using the ls command.

[[email protected] ~]# ls -l /home/shilpi  ls: cannot access          /home/shilpi: No such file or directory

Create User Without Home Directory in Linux

7. Create a User with Account Expiry Date

By default, when we add user's with the 'useradd' command user account never get expires i.e their expiry date is set to 0 (means never expired).

However, we can set the expiry date using the '-e' option, which sets the date in YYYY-MM-DD format. This is helpful for creating temporary accounts for a specific period of time.

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Here in this example, we create a user 'aparna' with account expiry date i.e. 27th August 2021 in YYYY-MM-DD format.

[[email protected] ~]# useradd -e 2021-08-27 aparna

Next, verify the age of the account and password with the 'chage' command for user 'aparna' after setting the account expiry date.

[[email protected] ~]# chage -l aparna  Last password change					: Jun 25, 2021 Password expires					: never Password inactive					: never Account expires						: Aug 27, 2021 Minimum number of days between password change		: 0 Maximum number of days between password change		: 99999 Number of days of warning before password expires	: 7

8. Create a User with Password Expiry Date

The '-f' argument is used to define the number of days after a password expires. A value of 0 inactive the user account as soon as the password has expired. By default, the password expiry value set to -1 means never expire.

Here in this example, we will set an account password expiry date i.e. 45 days on a user 'mansi' using '-e' and '-f' options.

[[email protected] ~]# useradd -e 2014-04-27 -f 45 mansi

9. Add a User with Custom Comments

The '-c' option allows you to add custom comments, such as the user's full name, phone number, etc to /etc/passwd file. The comment can be added as a single line without any spaces.

For example, the following command will add a user 'mansi' and would insert that user's full name, Manis Khurana, into the comment field.

[[email protected] ~]# useradd -c "Manis Khurana" mansi

You can see your comments in the '/etc/passwd' file in the comments section.

[[email protected] ~]# tail -1 /etc/passwd          mansi:x:1010:1013:Manis Khurana:/home/mansi:/bin/sh

10. Create User Login Shell in Linux

Sometimes, we add users who have nothing to do with the login shell or sometimes we require to assign different shells to our users. We can assign different login shells to each user with the '-s' option.

Here in this example, will add a user 'tecmint' without login shell i.e. '/sbin/nologin' shell.

[[email protected] ~]# useradd -s /sbin/nologin tecmint

You can check the assigned shell to the user in the '/etc/passwd' file.

[[email protected] ~]# tail -1 /etc/passwd          tecmint:x:1011:1014::/home/tecmint:/sbin/nologin

Part II – 5 Advance Usage of useradd Commands

11. Add a User with Specific Home Directory, Default Shell, and Custom Comment

The following command will create a user 'ravi' with home directory '/var/www/tecmint', default shell /bin/bash and adds extra information about the user.

[[email protected] ~]# useradd -m -d /var/www/ravi -s /bin/bash -c "TecMint Owner" -U ravi

Create User with Home Directory and Login Shell

In the above command '-m -d' option creates a user with a specified home directory and the '-s' option sets the user's default shell i.e. /bin/bash. The '-c' option adds the extra information about the user and the '-U' argument creates/adds a group with the same name as the user.

12. Add a User with Home Directory, Custom Shell, Custom Comment, and UID/GID

The command is very similar to above, but here we defining shell as '/bin/zsh' and custom UID and GID to a user 'tarunika'. Where '-u' defines the new user's UID (i.e. 100) and whereas '-g' defines GID (i.e. 1000).

[[email protected] ~]# useradd -m -d /var/www/tarunika -s /bin/zsh -c "TecMint Technical Writer" -u 1000 -g 100 tarunika

13. Add a User with Home Directory, No Shell, Custom Comment, and User ID

The following command is very much similar to the above two commands, the only difference is here, that we disabling the login shell to a user called 'avishek' with a custom User ID (i.e. 1019).

Here '-s' option adds the default shell /bin/bash, but in this case we set login to '/usr/sbin/nologin'. That means user 'avishek' will not able to login into the system.

[[email protected] ~]# useradd -m -d /var/www/avishek -s /usr/sbin/nologin -c "TecMint Sr. Technical Writer" -u 1019 avishek

14. Add a User with Home Directory, Shell, Custom Skell/Comment, and User ID

The only change in this command is, we used '-k' option to set the custom skeleton directory i.e. /etc/custom.skell, not the default one /etc/skel. We also used '-s' option to define different shell i.e. /bin/tcsh to user 'navin'.

[[email protected] ~]# useradd -m -d /var/www/navin -k /etc/custom.skell -s /bin/tcsh -c "No Active Member of TecMint" -u 1027 navin

15. Add a User without Home Directory, No Shell, No Group, and Custom Comment

The following command is very different than the other commands explained above. Here we used the '-M' option to create a user without the user's home directory and the '-N' argument is used that tells the system to only create a username (without group). The '-r' argument is for creating a system user.

[[email protected] ~]# useradd -M -N -r -s /bin/false -c "Disabled TecMint Member" clayton

For more information and options about useradd, run the 'useradd' command on the terminal to see available options.

# useradd

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