ubuntu@ip-10-137-13-238:/var/www/drupal/sites/all$ groups ubuntu
ubuntu : www-data adm dialout cdrom floppy audio dip video plugdev netdev admin
ubuntu@ip-10-137-13-238:/var/www/drupal/sites/all$ ls -l themes/
total 4
-rw-r--r-- 1 www-data www-data 767 Apr  3 21:29 README.txt
ubuntu@ip-10-137-13-238:/var/www/drupal/sites/all$ mkdir themes/test
mkdir: cannot create directory `themes/test': Permission denied
ubuntu@ip-10-137-13-238:/var/www/drupal/sites/all$