For people that install prestashop for 1st time if you get the following error:
Recursive write permissions for www-data user on ~/config/
Recursive write permissions for www-data user on ~/cache/
Recursive write permissions for www-data user on ~/log/
Recursive write permissions for www-data user on ~/img/
Recursive write permissions for www-data user on ~/mails/
Recursive write permissions for www-data user on ~/modules/
Recursive write permissions for www-data user on ~/themes/default-bootstrap/lang/
Recursive write permissions for www-data user on ~/themes/default-bootstrap/pdf/lang/
Recursive write permissions for www-data user on ~/themes/default-bootstrap/cache/
Recursive write permissions for www-data user on ~/translations/
Recursive write permissions for www-data user on ~/upload/
Recursive write permissions for www-data user on ~/download/
Do the following:
Add user to group www-data
Sudo chown -R user:www-data path to prestashop dir
Sudo chmod g+w -R path to prestashop dir
After install to make it more secure
sudo find . -type f -exec chmod 644 {} \;
sudo find . -type d -exec chmod 755 {} \;
give group write permissions to following dir's
sudo chmod g+w -R app/logs, app/cache, img, modules, translations, upload, download, mails, config, themes
Also edit .htaccess in your admin folder and add
order deny,allow
deny from all
allow from IP address
chmod 444 .htaccess