If, in Drupal 7, you need to change your files from Public to Private (or maybe even the other way around), using this script will help you with that process.

filefieldmod.sh

#!/bin/bash
# Make a back up of the file field data tables
drush sqlq "CREATE TABLE field_data_field_$1_bak AS SELECT * FROM field_data_field_$1;"
drush sqlq "CREATE TABLE field_revision_field_$1_bak AS SELECT * FROM field_revision_field_$1;"

#empty file field data tables
drush sqlq "TRUNCATE TABLE field_data_field_$1;"
drush sqlq "TRUNCATE TABLE field_revision_field_$1;"

echo "In the file field settings in Drupal, the option to change the field $1 to"
echo "private is now available. Do so and save the field."

read -p "Once finished, press Enter to continue."

#copy all data from the temp backup tables back in to the real tables

drush sqlq "INSERT INTO field_data_field_$1 SELECT * FROM field_data_field_$1_bak;"
drush sqlq "INSERT INTO field_revision_field_$1 SELECT * FROM field_revision_field_$1_bak;"

echo "In the FILE (FIELD) PATH SETTINGS are of the file field settinsg in Drupal, select the 'Retroactive Upgrade' option and save; it will move all the files to the right place in the file system and update the db to the new path (which may take a little while)."
read -p "Once you have completed this step, press Enter to continue."

#delete the temp storage tables
drush sqlq "DROP TABLE field_data_field_$1_bak;"
drush sqlq "DROP TABLE field_revision_field_$1_bak;"