How do I change the domain name on my xoops website?

The site name is stored in the mainfile.php in the xoops root. You will have to:

0- Chmod mainfile.php to 666 on server.(temporary)
1. Download mainfile.php from your sever
2- Make a copy as a backup (good practice)
3. Edit the XOOPS_URL to show your new domain name.
4- Upload the edited file back to the server, overwriting old version.
5. Set mainfile.php to be not writeable on the server (CHMOD 444)

This Q&A was found on XOOPS Web Application System : https://xoops.org/modules/smartfaq/faq.php?faqid=394