I'm installing fresh Backdrop on my laptop computer running Ubuntu 16.04.
I Installed fresh Apache2, MySQL, PHP, phpMyAdmin
I downloaded and expanded Backdrop into /var/www/html web root.
During Backdrop installation I get the message
Notice: Undefined variable: config_directory in ConfigFileStorage->initializeStorage() (line 995 of /var/www/html/core/includes/config.inc).
The directory could not be created or could not be made writable. To proceed with the installation, either create the directory and modify its permissions to make it writable, or adjust the permissions on the parent directory to allow the installer to create it automatically. For more information, see the Installation Instructions page.
It would be good if the error message gave the path and filename it can't access or create.
I have tweaked permissions on directories and files using the installation instructions and I can't figure out where the problem is.
I used the settings.php names for the config files and created them but that didn't satisfy the installer.
$config_directories['active'] = './files/config_385f24349ad59b071009652666c1ec26/active';
$config_directories['staging'] = './files/config_385f24349ad59b071009652666c1ec26/staging';
I also tried using
My home directory is
I used the directory created by apache2 for web root:
/var/www/html and changed directory owner and group from root:root to jwalling:jwalling
$database has the correct credentials for the database
When I get Backdrop working on my laptop I'll do an install on DigitalOcean using Ubuntu 16.04.
I'll keep plunking on directories and filenames, but if any one has a suggestion I'll jump on it.
-- John Walling
I'm not sure about a solution, but I thought I would let you know I have the exact same setup as you (Ubuntu 16.04, Apache, mysql, etc) and the install works fine for me. When you find the solution I expect it will be something simple. When you extracted Backdrop, were you root, or a sudo user? I did my extraction and install as root. Did you try fully opening the permissions of /var/www/html/ just to see what happens? Perhaps that is where "The directory could not be created or could not be made writable" applies.
After I installed and tested Backdrop on my local Ubuntu machine, I followed the same basic procedure to install it on my shared hosting site, and everything worked OK there as well. That's why I think the solution might be something simple such as permissions on one isolated folder.
Best wishes with your effort....