If you can’t open Rar files, the matter is that the Files Management Graphical Tool cannot understand rar 3.0 and following versions.
If you install unrar-free packet, you will be able of opening some rar files, but not all.
Here you have the way of opening Rar files in Ubuntu
The best way is going to /etc/apt and editing sources.list file. Add in the botton of the file this line:
deb http://archive.ubuntu.com/ubuntu/ breezy multiverse
It will active the access to a set of tools and programs that is not supported by the Ubuntu Team, but are working properly.
Then write in the sell apt-get update and then apt-get install unrar, and here you have unrar installed.
And then, let use it. If we want to extract files from a RAR file, we go to the directory in which this file is and write:
unrar x File.rar ./Directory
When File.rar been the source Rar file, and Directory the directory in which we want to uncompress the file.