It's been a while that I do nothing with Cacti. So, I decided to upgrade Cacti from version 0.8.7b ( http://bxtra.net/Articles/2008-09-18/Steps-how-install-Cacti-CentOS-52-DirectAdmin ) to version 0.8.7d.

1. Get Cacti version 0.8.7d

cd /var/www/html
wget http://www.cacti.net/downloads/cacti-0.8.7d.tar.gz

2. Change directory of Cacti 0.8.7b (Old) to something Else. Then, extract Cacti 0.8.7d and change directory name to the one we use.

mv cacti cacti_old_version
tar xzvf cacti-0.8.7d.tar.gz
mv cacti-0.8.7d cacti

3. Set configuration setting in a new config file.

Start by open an old configuration file.

cd /var/www/html/cact_oldversion/include
nano -w config.php

Take a note on all configuration settings that look like below:

$database_default = "cacti";
$database_hostname = "localhost";
$database_username = "cactiuser";
$database_password = "somepassword";

Then, copy it to a new configuration file below :

cd /var/www/html/cacti/include
nano -w config.php

4. Set the appropriate permissions on Cacti directory. In DirectAdmin, You may get 500 Internal Server Error if you don't do this. So, you need to do the following:

cd /var/www/html
chown -R webapps:webapps cacti

5. Update Cacti Database by using Web Browser to enter to your Cacti page.

http://your-server/cacti/

Follow the on-screen steps to upgrade your database. Then, you can log on and use Cacti as usual.