Prerequisites
On a Debian 9 GNU/Linux, install the wordpress package and adjust file ownership and permissions for www-data user.
sudo apt-get install -y wordpress sudo chown -R www-data:www-data /usr/share/wordpress/ sudo chmod -R g+w /usr/share/wordpress/
Configure Apache
Copy the following into /etc/apache2/conf-available/wordpress.conf.
Alias /blog /usr/share/wordpress <Directory /usr/share/wordpress> Options FollowSymLinks AllowOverride Limit Options FileInfo DirectoryIndex index.php Require all granted </Directory>
Enable the configuration and reload apache.
sudo a2enconf wordpress sudo systemctl reload apache2