Not able to change the settings.php I am working on drupal commons, and using pantheon servers for hosting. The major problem I am facing is the server database config issues. I am not able to change the settings.php file. Also Pantheon every now and then changes their db server password. How can I control this ? is there any server variable for the db instance, port, user id, password ?
Drupal removes "write" permission from settings.php, so to edit it, you need to give this permission back.

SSH

chmod u+w sites/default/settings.php


FTP, SFTP and alike

Use your cilent, and just tick appropriate checkbox. Like this: