On the initial surface, upgrading Drupal appears complex, when in actuality it’s very rudimentary. A lot of the tutorials and resources on how to upgrade are just plain confusing and not to the point.
The following is a list of command lines and steps in order to upgrade Drupal quickly and easily in 3 EASY STEPS! It just can’t get easier, and I have yet to see one posting that includes this way of doing it, which is really just the quickest/easier/cleanest/simplest way to get it done.
Go to your root directory (one step below public_html), download Drupal, and unpack it. Replace 6.x with the new version you are upgrading to:
wget http://ftp.drupal.org/files/projects/drupal-6.x.tar.gz tar -zxf drupal-6.x.tar.gz
Sync the new files up with your current install:
rsync -av drupal-6.x/ public_html/
Go to your domain and run the update script:
The entire upgrade process takes only a few minutes. I dare and challenge you to find a quicker and simpler way of upgrading Drupal — because there isn’t one.
Update: I was mistaken; there is an easier method. It’s called Drush :)