This is accomplished by using the "chmod" command. The chmod is followed by a 3 digit number used to indicate the permissions required. The first 3 digit indicated the owner's permission, the second digit the user group's permission and the third is for all others.
The number coding is as follows:
6: read and write
5: read and execute
4: read only
3: write and execute
2: write only
1: execute only
Write the following command in terminal to give full permissions to the file named "amuk".
$ chmod 777 amuk
Hence, the command chmod 777 amuk will give full access to everybody to the file named "amuk". "chmod 600 amuk" will give only the owner of the file "amuk" the permission to view and edit the file. No one else will have any rights to it.
I hope this blog will help you to understand the concept of changing permissions in Ubuntu.