How to enable php extensions and database support?

Today, I am trying to install Drupal on Amazon ec2 instance. The process is this pretty much the same as installing Joomla. But I encountered two weird  problems:

PHP extensions Disabled

Drupal requires you to enable the PHP extensions in the following list (see the system
requirements page for more information): gd

And;

Database support Disabled.

Your web server does not appear to support any common PDO database extensions. Check with
your hosting provider to see if they support PDO (PHP Data Objects) and offer any databases
that Drupal supports.

After a while of searching, just got the fucking answers.

1. PHP extensions Disabled

Just do : sudo apt-get install php5-gd
then restart your instance. It should be fine with you.

For another, re-configure your php5 with two extra config:

--with-pdo-mysql=mysqlnd
--with-gd

and then 'make&&sudo make install'