Fix Drupal files permissions (credits to James Wilmot)

drupal-fix-file-permissions.sh

#!/bin/bash

#
# A script to fix file permissions in the given 
# files directory for drupal
#
# Usage:
#  - set files directory variable to point at the files
#    drupal installation files directory
#  - run script

files_dir="sites/default/files"

sudo chown -R :www-data $files_dir
chmod g+ws $files_dir
find $files_dir -type d -exec chmod g+ws {} \;
find $files_dir -type f -exec chmod 664 {} \;