diff --git a/setup/start.sh b/setup/start.sh
index 22759c60..022600d3 100755
--- a/setup/start.sh
+++ b/setup/start.sh
@@ -87,17 +87,28 @@ if [ -z "$SKIP_NETWORK_CHECKS" ]; then
 	. setup/network-checks.sh
 fi
 
+# For the first time (if the config file (/etc/mailinabox.conf) not exists):
 # Create the user named "user-data" and store all persistent user
 # data (mailboxes, etc.) in that user's home directory.
-if [ -z "$STORAGE_ROOT" ]; then
-	STORAGE_USER=user-data
-	if [ ! -d /home/$STORAGE_USER ]; then useradd -m $STORAGE_USER; fi
-	STORAGE_ROOT=/home/$STORAGE_USER
-	mkdir -p $STORAGE_ROOT
-	echo $(setup/migrate.py --current) > $STORAGE_ROOT/mailinabox.version
-	chown $STORAGE_USER.$STORAGE_USER $STORAGE_ROOT/mailinabox.version
+#
+# If the config file exists:
+# Apply the existing configuration options for STORAGE_USER/ROOT
+STORAGE_USER=$([[ -z "$DEFAULT_STORAGE_USER" ]] && echo "user-data" || echo "$DEFAULT_STORAGE_USER")
+STORAGE_ROOT=$([[ -z "$DEFAULT_STORAGE_ROOT" ]] && echo "/home/$STORAGE_USER" || echo "$DEFAULT_STORAGE_ROOT")
+
+# Create the STORAGE_USER if it not exists
+if [ ! $(id -u $STORAGE_USER >/dev/null 2>&1;) ]; then
+	useradd -m $STORAGE_USER
 fi
 
+# Create the STORAGE_ROOT if it not exists
+if [ ! -d $STORAGE_ROOT ]; then
+	mkdir -p $STORAGE_ROOT
+fi
+
+echo $(setup/migrate.py --current) > $STORAGE_ROOT/mailinabox.version
+chown $STORAGE_USER.$STORAGE_USER $STORAGE_ROOT/mailinabox.version
+
 # Save the global options in /etc/mailinabox.conf so that standalone
 # tools know where to look for data.
 cat > /etc/mailinabox.conf << EOF;