Create a file name .bash_aliases in home directory Then when we need to create a alias open that file in text editor(in my case: Gedit) with root privileges. sudo gedit ~/.bash_aliases then create whatever alias you want inside the text file eg: alias update="sudo apt-get update" and save the text file. as you may have noticed I assigned "update" to "sudo apt-get update" now whenever I type in the command 'Update' on to the terminal it will run "sudo apt-get update"
In the latest versions of Ubuntu, ~/.bashrc automatically sources ~/.bash_aliases, so permanent aliases are best put into this file instead. previously we used to put permanent aliases on  ~/.bashrc