Explicitly ignore the failure of dd

playbooks/roles/edx_ansible/templates/pre-box.j2

@@ -17,5 +17,7 @@ find / -type d -path '*/.cache/pip' -print -exec rm -rf '{}/*' \;
 find /edx/app -name '*.pyc' -delete
 
 # Last thing: fill the disk with zeros so they'll compress well.
-dd if=/dev/zero of=/empty bs=1M
+# The dd command fails because the disk fills, which is the point, so silence
+# the error.
+dd if=/dev/zero of=/empty bs=1M || true
 rm -f /empty