Where can get a relieable tutorial about install Asterisk 1.2 for Centos 5?
check the wiki for installs of 1.2 on CentOS 4 - should be nearly the same for CentOS 5.
Why are you installing 1.2? 1.4 has been stable for a year or more and 1.6 was recently released (though I would not use it for a production install of 15-20 or more extensions for at least a couple of months).
Because Asterisk 1.4 or 6 come with GUI interface thats mean some codes that I cannot change or I can have some trouble or error message.
None of the base asterisk installations include a gui. They are either included in a distribution such as AsteriskNow, Druid, etc…, or added on like FreePBX, Thirdlane, etc…
As far as guides, I’m pretty sure there are a few around that are good, but If you are just getting into asterisk. I’d suggest using the book “Asterisk: The Future of Telephony” 2nd edition as a guide. Chapter 3 covers the installation. downloads.oreilly.com/books/9780596510480.pdf