How to overcome the error "Unable to connect to the filesystem" in Wordpress using Ubunto 16.04 and trying to utilise FTPS SSL [closed]

Question

I am running:

Ubuntu 16.04.3 LTS
NGINX 1.10.3 
ufw
PHP 7.0.22
Wordpress 4.9

After following the steps I outline below I am receiving the following error when I try to install a theme via FTPS (SSL), or plugin from the Wordpress Admin dashboard:

Unable to connect to the filesystem. Please confirm your credentials.

The steps I have taken to enable FTPS SSL access for Wordpress on the server were taken from this Digital Ocean article: https://www.digitalocean.com/community/tutorials/how-to-configure-secure-updates-and-installations-in-wordpress-on-ubuntu

The article was written for Ubunto 14.04, but barring one problem with packages (outlined below), I was able to follow it without any problem.

Steps Followed So Far

Create user account for Wordpress:

sudo adduser wp-user

Give the Wordpress user permission over all files from root www:

cd /var/www/html
sudo chown -R wp-user:wp-user /var/www/html

Create SSH keys for wp-user:

sudo su - wp-user
ssh-keygen -t rsa -b 4096

Told ssh-keygen to store the keys here: /home/wp-user/wp_rsa

Gave Wordpress user ownership of keys, and set www-data as group owner:

sudo chown wp-user:www-data /home/wp-user/wp_rsa*
sudo chmod 0640 /home/wp-user/wp_rsa*

Created SSH folder, set permisions, moved key into there:

sudo mkdir /home/wp-user/.ssh
sudo chown wp-user:wp-user /home/wp-user/.ssh/
sudo chmod 0700 /home/wp-user/.ssh/
sudo cp /home/wp-user/wp_rsa.pub /home/wp-user/.ssh/authorized_keys

Set permissions on authorized keys folder:

sudo chown wp-user:wp-user /home/wp-user/.ssh/authorized_keys
sudo chmod 0644 /home/wp-user/.ssh/authorized_keys

Restricted login to the server:

sudo nano /home/wp-user/.ssh/authorized_keys
[then added] from="127.0.0.1 " [to the start of the file]

Part of the guide I wasn't able to follow:

The next steps are:

sudo apt-get install php5-dev libssh2-1-dev libssh2-php

I'm using php7, so instead I used:

sudo apt-get install php7.0-dev libssh2-1-dev libssh2-1

These executed successfully.

Finally the guide says to edit the wp-config file adding these defines at the end:

define('FTP_PUBKEY','/home/wp-user/wp_rsa.pub');
define('FTP_PRIKEY','/home/wp-user/wp_rsa');
define('FTP_USER','wp-user');
define('FTP_PASS','');
define('FTP_HOST','127.0.0.1:22');

Which I did. I restarted NGINX. Site loaded fine, but the above error was reported when I tried to upload a theme, using FTPS (SSL).

Troubleshooting

1. I've have checked the /home/wp-user/.ssh/authorized_keys and the SSH key is in that file.

2. I have checked that port 22 is open. Netstat reports:

   tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN

How can I overcome this error? What might I try next to try to further troubleshoot?

Answer 1

Just add this line at the end of wp-config.php file

define("FS_METHOD", "direct");

Reload the webpage and try the installation again.

Answer 2

This was the best answer I got initially but it did not help to solve it completely. I complemented it with someone's answer from the following forum: Wordpress asking for FTP Credentials | DigitalOcean

Running the following commands fix it:

sudo chown username:www-data /var/www -R 
sudo chmod g+w /var/www -R