Reboot a server from the command line, run:

sudo shutdown -r now

Restart Apache, run:

sudo shutdown -r now

FTP to wordpress (var/www)

sudo chown -R www-data /var/www/html

WordPress “Could not create directory”

chown -R www-data:www-data /var/www

Install phpMyAdmin on Ubuntu with preinstalled WordPress (https://www.digitalocean.com/community/tutorials/how-to-install-and-secure-phpmyadmin-on-ubuntu-14-04)

sudo apt update
sudo apt install phpmyadmin php-mbstring php-gettext
sudo phpenmod mbstring
sudo systemctl restart apache2
sudo ln -s /usr/share/phpmyadmin /var/www/html

Note: The last line is for URL https://your-ip-or-domain/phpmyadmin/