System: Ubuntu 9.04
Install XeTeX
$ sudo apt-get install texlive-xetex
Download Akshar fonts and install
$ cd /usr/share/fonts/truetype/ttf-kannada-fonts
$ sudo wget http://www.kamban.com.au/fonts/akshar.ttf
$ sudo fc-cache
Note: You may have to install ttf-kannada-fonts package if don't see the above directory.
Create a TeX file containing Kannada Unicode text. See attached ondu.tex for example.
Convert the .tex file to .pdf using xelatex command
$ xelatex ondu.tex
View the output file -- ondu.pdf with
$ evince ondu.pdf