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🦑Adding, Removing, and Granting Sudo Rights to Users on CentOS:

Log into the CentOS system as root or any user with sudo privileges.

First, let's add sudo privileges to the new user.

1) Add sudo users to CentOS

Let me create a new user named "senthil".

To do this, I will run the following command as root from the terminal:

# adduser senthil
Set a password for the new senthil user:

# passwd senthil
He is not yet authorized to perform any administrative tasks.
Let's check if the senthil user can use the sudo command:
# sudo -l -U senthil
Output example:

User senthil is not allowed to run sudo on centos8
That's right, it is not yet allowed to run sudo on my CentOS 8 system.
Let's give it sudo rights now.

2) Grant sudo privileges to users on CentOS.
To add a regular user to the sudoers group, you need to add him to the wheel group.

For those of you curious, wheel is a special group on some Unix-like operating systems.

All members of the wheel group are allowed to perform administrative tasks.

The Wheel group is similar to the sudo group on Debian based systems.

We can add users to sudoers in two ways.

The first way is to use the chmod command.

2.1. Adding users to sudoers using usermod command on CentOS
Now, let's grant sudo privileges to the newly created user “senthil” by adding him to the wheel group using the usermod command as shown below:

# usermod -aG wheel senthil
Here -aG refers to the optional group.

In our case, this is the wheel group.

That's it, we have just granted sudo permissions to senthil.

Let's check if the user is in the sudoers list using the command:

# sudo -l -U senthil
Conclusion:

Matching Defaults entries for senthil on centos8:
!visiblepw, always_set_home, match_group_by_gid,
always_query_group_plugin, env_reset, env_keep="COLORS DISPLAY
HOSTNAME HISTSIZE KDEDIR LS_COLORS", env_keep+="MAIL PS1 PS2 QTDIR
USERNAME LANG LC_ADDRESS LC_CTYPE", env_keep+="LC_COLLATE
LC_IDENTIFICATION LC_MEASUREMENT LC_MESSAGES", env_keep+="LC_MONETARY
LC_NAME LC_NUMERIC LC_PAPER LC_TELEPHONE", env_keep+="LC_TIME LC_ALL
LANGUAGE LINGUAS _XKB_CHARSET XAUTHORITY",
secure_path=/sbin\:/bin\:/usr/sbin\:/usr/bin

User senthil may run the following commands on centos8:
(ALL) ALL
As you can see in the last line of the above output, user "senthil" can now execute all commands.

2.2. Add users to sudoers by editing the sudoers config file on CentOS
Another way to add users to the sudoers list is to directly add him / her to the sudoers config file.

Edit the sudoers config file with the command:

# visudo
The system will open the / etc / sudoers file in your Vi editor or whatever you have in your $ PATH.

Scroll down until you find the following entry:

root ALL=(ALL) ALL
Add the following line immediately after the above entry:
senthil ALL=(ALL) ALL
Here the line ALL = (ALL) ALL indicates that the user "senthil" can execute any command on any host.
Replace “senthil” with your username.
Save and close the file.
That's all.
The user “senthil” has been added to the sudoers list.
2.3. Checking sudo users on CentOS
Log out of the current session and log in again as the newly created sudo user.

Alternatively, you can switch to another user directly without leaving your current session using the following command:

# sudo -i -u senthil
Now check if the user can perform any administrative task with sudo privileges:

$ sudo dnf update

3) Remove the sudo privileges from the CentOS user.
We can revoke sudo rights from a user without completely deleting their account.

To revoke sudo permissions from a user, simply run the following command as root:

# gpasswd -d senthil wheel

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