groupadd www-pub
usermod -a -G www-pub usera    # must use -a to append to existing groups
usermod -a -G www-pub userb
groups usera    ## display groups for user

chown -R root:www-pub /var/www    # -R for recursive

chmod 2775 /var/www

find /var/www -type d -exec chmod 2775 {} +

find /var/www -type f -exec chmod 0664 {} +