Grayside.Org

This is a straightforward walkthrough to installing Drupal in multi-site "mode" without needing to make any configuration changes to your webserver. This tutorial assumes your webserver will follow symlinks.

Download Drupal

Download the latest Drupal release from http://drupal.org. Put it inside a directory named, say drupal_multisite. It does not need to be in the webserver's directories.

Create Your Sites Directories

Even if you are only going to start with one site, follow these steps.

1. Go to path/to/drupal/sites
2. Copy default/default.settings.php to default/settings.php
3. Copy the default directory, name it www.example.com.site1. Repeat for site2, site3, and so on.

Set Up the Database

This section is only relevant if you have "root" access to the database. If you do not have this kind of access, request your system administrator give you a new database for each site. Your database account will need the following permissions:

If you are doing this yourself with that root access, login to MySQL and get to work.

Create the Database User

If necessary, create a database user as follows:
CREATE USER 'username' IDENTIFIED BY 'password';

Create a Database for Each Site

Each site needs it's own database. I suggest naming them something like multisite_sitename. In this example, I'm going drupal_site#.
CREATE DATABASE 'drupal_site1';

Grant the Database User Permission

The database user will need permission to do all the drupal-ish things on each database.

Create Symlinks

Go to the drupal_multisite directory you created above to contain your current drupal installation, create a symlink from drupal_current to drupal-X.Y:
ln -s drupal-6.13 drupal_current
This allows you to upgrade Drupal Core and only need to change one symlink.

Next, make the webserver aware of your Drupal sites. Go to the root directory of your webpages. Create a symlink to the drupal_current symlink you just created from <site#>.

Install Drupal

Go to www.example.com/site1/install.php. Follow the steps.
Next, go to www.example.com/site2/install.php

Done.