Give the ability to a unprivileged user to manage a website

gistfile1.txt

--- For the demonstration ---

root@work /# mkdir /var/www
root@work /# useradd www-data
root@work /# chown www-data:www-data /var/www

# Add the user to the www-data group
root@work /# usermod -a -G www-data user

# Use the setgid bit to let subdirectories inherit from the group
root@work /# chmod 2775 /var/www

# Use acls to set default group permissions
root@work /# setfacl -d -m group:www-data:rwx /var/www

--- For an existing website ---

root@work /# chgrp -R www-data /var/www/site
root@work /# chmod -R 775 /var/www/site
root@work /# find /var/www/site -type d -exec chmod 2775 {} +
root@work /# find /var/www/site -type d -exec setfacl -R -m group:www-data:rwx {} +
root@work /# find /var/www/site -type d -exec setfacl -R -d -m group:www-data:rwx {} +