Sudo Command in Linux

Using sudo command you can perform the actions and operations as root user. It’s the mostly used command for Linux user. It’s always recommended to login as a sudo user instead of as root and perform task. You can give limited administrative privileges to sudo users without providing them root password.

This guide will explains how to use the sudo command.

Install Sudo (sudo command not found)#

Now a days, with the modern Linux distributions, sudo package comes pre-installed. You can check either sudo package is installed or not by typing sudo in terminal. If sudo is not installed it will show sudo command not found otherwise it will show a help message.

You can install sudo easily using package manager if the sudo package is not installed.

Install Sudo on Ubuntu and Debian#

apt install sudo

Install Sudo on CentOS and Fedora#

yum install sudo

Add User to Sudoers#

In latest Linux distributions you can give sudo access to user just by adding them to sudo group which defined in the sudoers file. Each member of this group can perform any command as root.

The sudo group name will be different as per distributions. For RedHat based distros like CentOS and Fedora will have the name of the sudo group is wheel. Run below command to add the user to wheel group:

usermod -aG wheel username

For Debian and Ubuntu type following to grant with sudo access:

usermod -aG sudo username

Here, don’t forget to replace username with your actual name.

If you have a Ubuntu system, you notice that by default root user is disabled for the security purpose. Ubuntu creates a initial user with the member of sudo group so can have sudo privileges.

You can also give limited access to users instead of adding them to sudo group. If you would like to give mkdir command as sudo to user tecnstuff then just type:

sudo visudo

Commonly, the visudo command opens the /etc/sudoers file with text editor. Append below line to file:

tecnstuff  ALL=/bin/mkdir

Save the file and quit.

How to Use Sudo#

The basic syntax for sudo command is as below:

sudo OPTION.. COMMAND

It has different options for different purpose but mostly sudo command is used in basic form, without any options:

sudo command

You just have to prefix the command with sudo to use sudo. Here, command is the command for which you want to sudo.

Sudo will read the /etc/sudoers file and check if the user have sudo access or not. At the first time, it will ask to enter user password and on success command will be execute as a root.

For example, to list all files inside the /etc/nginx directory you would use:

sudo ls /etc/nginx

[sudo] password for tecnstuff:
conf.d          koi-win            nginx.conf       sites-enabled
fastcgi.conf    mime.types         proxy_params     snippets
fastcgi_params  modules-available  scgi_params      uwsgi_params
koi-utf         modules-enabled    sites-available  win-utf

Password Timeout#

Within a certain time, you don’t need to enter the password again to use another sudo. By default, the timeout is about 5 minutes for sudo. You can change the default timing by editing sudoers file. Run below command to open file:

sudo visudo

Find out the Defaults env_reset line in file and change it to as below:

Defaults env_reset, timestamp_timeout=15

Run a Command as a Other User#

The sudo command is not only use to perform as root but you use it to run any command as another user also.

The option -u will allows you to run a command as a specified user.

In the below example we are using sudo to run the whoami command as a use john:

sudo -u john whoami

It will returns the current user name john

Conclusion#

In this guide, you learned how to use the sudo command and grant sudo privileges to users. If you have any query or suggestion, please comment below.