Add 'README.root-user' file.

README.root-user

@@ -0,0 +1,15 @@
+# The root@localhost user account created by mysql_install_db is created with the 
+# ability to use two authentication plugins. 
+#
+# First, it is configured to try to use the unix_socket authentication plugin. This 
+# allows the root@localhost user to login without a password via the local Unix 
+# socket file defined by the socket system variable, as long as the login is 
+# attempted from a process owned by the operating system root user account. 
+#
+#   CREATE USER root@localhost IDENTIFIED VIA unix_socket OR mysql_native_password USING 'invalid'
+#   CREATE USER mysql@localhost IDENTIFIED VIA unix_socket OR mysql_native_password USING 'invalid'
+#
+
+# We can do:
+#
+ALTER USER root@localhost IDENTIFIED VIA unix_socket OR mysql_native_password USING PASSWORD('$MYSQL_ROOT_PW'