Pretty basic but still posting! Tested with Ubuntu 14.4 LTS Trusty Tahr.
Via command line. You will have to first install unrar apt package
1) open xterm , or gnome-terminal
2) sudo apt-get install unrar
This will install the unrar package under /usr/bin/unrar so you can run the unrar command everywhere! you can check this via command “which unrar”
3) That’s about it. Go to your folder in which you have xyz.rar file.
4) unrar t xyz.rar (to test archive for correctness without extracting anything from it)
5) unrar x xyz.rar to extract files from the rar file onto your current directory.