On Red Hat, the sudo command is not enabled by default, and you’ll need to enable it. To do this, you need to use a command called visudo to edit the sudo command’s configu- ration file, /etc/sudoers. To do this, you need to log on as the root user and run the visudo command.
# visudo
As you can see from the # command prompt, you’re logging in as the root user and you’re executing the visudo command. This opens an editing application that looks much like the vi or vim editor. Inside this file is the following line:
# %wheel ALL=(ALL) ALL

You need to uncomment the line and write and quit the file using the same commands you would with vim by typing the colon character, :, and w and q followed by Enter, or :wq. This enables any member of a group called wheel to use the sudo command. You can then add a user to the wheel group like so:
# usermod –G wheel ataylor
Again, you specify the group, wheel, with the -G option and the name of the user you want to add to the group last. Now the ataylor user can make use of the sudo command.
Some useradd Command-Line Options
Option Description
-c Add a description of the user
-d homedir The user’s home directory
-m Create the user’s home directory
-M Do not create the user’s home directory (Red Hat only)
-s shell Specify the shell the user will use

User Default Settings
Your new user will also be created with a variety of defaults (e.g., the setting for the you can display the current defaults using the following command:
$ sudo /usr/sbin/useradd -D