Steps to make a normal users as a sudo users.
Login as a root user in ‘Terminal’.
Type the command
$ sudo adduser username admin and then press enter
Now continue using your computer.If you want to install any package then mention sudo in front of the command and go ahead with steps.
Here are the steps to create a rar file in linux.
Install a rar package by the following command
$ sudo apt-get install rar
After that just typed the command to create a rar archive of a file or directory
$ sudo rar a filename.rar input
filename.rar is the output file.
input is nothing but a directory.