how can i unzip rar. files

open terminal

apt-get install unrar

then .rar files can extract normal way.

How to move mysql database to another drive or partition

First copy database to current mysql directory
(my source directory is /home/viranga/mysql1/ and destination is /var/lib/mysql/ )

 sudo cp -r /home/viranga/mysql1/database /var/lib/mysql/database

Give permission  to it.

sudo  chown -R mysql:mysql /var/lib/mysql/database