# Upgrading from 3.0.1 to 3.0.2

Before performing an update you should take your site offline by replacing the index.php file with a static one.

## Step 1: Update your CodeIgniter files

Replace all files and directories in your system/ directory.

注解

If you have any custom developed files in these directories, please make copies of them first.

## Step 2: Update your application/config/constants.php file

The application/config/constants.php file has been updated to check if constants aren't already defined before doing that, making it easier to add an environment-specific configuration.

注解

If you've made modifications to this file, please make a backup first and cross-check the differences first.