Mod rewrite problem with Ubuntu

[eluser]Mohammed Zayan[/eluser]
I try

Code:

RewriteEngine On
RewriteBase /zayanit/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php?/$1 [L]

And

Code:

RewriteEngine On
RewriteBase /zayanit/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]

It doesn't work. I use Ubuntu 11.04