To update drupal manually, download and unzip drush, then go into the directory where you unzipped, and run:

./drush pm-update projects drupal-7.33 -r  <path to your drupal installation>

I later had to rebuild content access permissions. With drush:

sudo ./drush php-eval ‘node_access_rebuild();’ -r<path to your drupal installation> -y -l http://<url> -v

I had to run as non-root (ran into some issues with root).   This command took half an hour (?), as I ran it several times with no success. On my vm, I also had to change includes/common.inc ‘s drupal_set_time_limit to never timeout (set $time_limit to 0)