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We can only execute certain commands as the root user using sudothe command. The root user is also called sudoa user. In CentOS, we can add users by adding them to wheelthe group, or by adding them to /etc/sudoersfiles under the directory sudo.

Adding users to wheela group

Let's consider that you have a sudouser that is not a superuser. To add that user to wheelthe group, we run the following command as another already existing superuser.

usermod -aG wheel username

usernameis wheelthe name of the user to be added to the group.

usermod -aG wheel zeppy

It zeppyadds to wheelthe group.

To confirm if the user is added to wheelthe group, we use whoamithe command.

sudo whoami

This command prompts us for a password, and if the password is correct and the user is in wheelthe group, rootit will be printed in the terminal.

Output:

root

If the user is not wheelin the group, we will get an error message user is not in the sudoers file.

Adding Users in Sudoers File

Users with sudopermissions /etc/sudoersare configured in the config file. We can add users by modifying sudoersthe config file or /etc/sudoers.dby adding a new configuration file in the config directory sudo.

We use visudothe command to edit /etc/sudoersthe file, which uses vimthe editor. visudoThe command checks the file for syntax errors before saving.

To edit the file using nanoeditor /etc/sudoers, we use the following command.

EDITOR=nano visudo

If we want to allow the user to run commands without being prompted for a password sudo, we use the command to open /etc/sudoersthe file.

visudo

If you get permission denied error, try using the command below.

sudo visudo

Now /etc/sudothe file will be opened and we need to add the following line at the end of the file.

username ALL=(ALL) NOPASSWD:ALL

Here, usernameis the name of the user we want to allow.

Now, we need to save the file before exiting the editor.

We can also allow users to execute only certain commands without a password.

zeppy ALL=(ALL) NOPASSWD:/bin/mkdir,/bin/rmdir

This allows the and commands zeppyto be executed without a password ./bin/mkdir/bin/rmdir

We can also /etc/sudoers.denable permissions for users to run commands by creating a configuration file under the directory.

We have to add /etc/sudothe same content in the file as in the .

zeppy ALL=(ALL) NOPASSWD:/bin/mkdir,/bin/rmdir

This allows the and commands zeppyto be executed without a password ./bin/mkdir/bin/rmdir

The benefit of this approach is that it makes things a lot easier to manage because we can create a separate file for each user's file name.