As part of the pre-flight check Joomla checks for the write permissions of the file configuration.php. By default it is likely set to No – unwritable.
The install can proceed, but the file will need to be updated with the relevant settings.
An alternative approach is to make the file writeable for the duration of the installation and then to set its permissions back once the installation has been completed.
The file configuration.php is located in the riot of the website.
The indication that the file is not writeable may also indicate that the file does not exist.
There is a template file in the directory /installation/model. Copy this file into the root of the website. For the duration of the installation set its permissions to 777. You may need to go back a step to come forward for the Joomla installation to discover the added file.
Once Joomla has been installed set the configuration.php file to have permissions 644 and remove the installation directory.
