How to resolve configuration.php not writable

It's Best to Forget this Warning Message and Follow..
If you try to copy the configuration.php-dist in configuration.php and give it 777 permissions you will find after a bigger problem...

So Just Follow installation Process until the end and after:
Under the "Remember to delete Installation Directory" there is the content
to paste in the configuration.php, select and copy it.
-Create a configuration.php and give it 777 permission

touch configuration.php

sudo chmod 777 configuration.php

-Open the file with your favorite Editor and Paste it inside