You can do this in 2 methods- however, IMHO method-2 usually works great for me.
Step 1: Verify the Wheel Group is Enabled
Your CentOS 7 installation may or may not have the wheel group enabled. Open the configuration file by entering the command:
Scroll through the configuration file until you see the following entry:
## Allows people in group wheel to run all commands # %wheel ALL=(ALL) ALL
If the second line begins with the # sign, it has been disabled and marked as a comment. Just delete the # sign at the beginning of the second line so it looks like the following:
%wheel ALL=(ALL) ALL
Then save the file and exit the editor.
Note: If this line didn’t start with a # sign, you don’t need to make any changes. The wheel group is already enabled, and you can close the editor.
Step 2: Add User to Group
To add a user to the wheel group, use the command:
usermod –aG wheel UserName
As usual, replace UserName with the name of the user receiving sudo privileges.
Step: 3 Switch to the Sudo User
Switch to the new (or newly-elevated) user account with the su (substitute user) command:
su - UserName
Enter the password if prompted. The terminal prompt should change to include the UserName. Enter the following command to list the contents of the /root directory:
sudo ls -la /root
The terminal should request the password for UserName. Enter it, and you should see a display of the list of directories. Since listing the contents of /root requires sudo privileges, this works as a quick way to prove that UserName can use the sudo command.
Alternative: Add User to Sudoers Configuration File
If there’s a problem with the wheel group, or administrative policy prevents you from creating or modifying groups, you can add a user directly to the sudoers configuration file to grant sudo privileges.
Step 1: Open the Sudoers File in an Editor
In the terminal, run the following command:
Step 2: Add the New User to file
Scroll down to find the following section:
## Allow root to run any commands anywhere root ALL=(ALL) ALL
Right after this entry, add the following text:
UserName ALL=(ALL) ALL
Replace UserName with the username you created in Step 2. This section should look like the following:
## Allow root to run any commands anywhere
root ALL=(ALL) ALL UserName ALL=(ALL) ALL
Save the file and exit.
Step 3: Test Sudo Privileges for the User Account
Switch user accounts with the su (substitute user) command:
su - UserName
Enter the password for the account, if prompted. The terminal prompt should change to include UserName. List the contents of the /root directory:
sudo ls - la /root
Enter the password for this user when prompted. The terminal should display a list of all the directories in the /root directory.