Authentication Plugins the plugin refuses the connection even for  valerie  if the connection is made using a different protocol, such as TCP/IP. To permit both the  valerie  and  stephanie  operating system users to access MySQL through socket file connections that use the account, this can be done two ways: To access the account, both  valerie  and  stephanie  specify  --user=valerie  at connect time. MySQL includes a test plugin that checks account credentials and logs success or failure to the server error log. This is a loadable plugin (not built in) and must be installed prior to use. The test plugin source code is separate from the server source, unlike the built-in native plugin, so it can be examined as a relatively simple example demonstrating how to write a loadable authentication plugin. This plugin is intended for testing and development purposes, and is not for use in production environments or on servers that are exposed to public networks. The following table shows the plugin and library file names. The file name suffix might differ on your system. The file must be located in the directory named by the  plugin_dir  system variable. Table 6.22 Plugin and Library Names for Test Authentication The following sections provide installation and usage information specific to test pluggable authentication: For general information about pluggable authentication in MySQL, see Section 6.2.17, “Pluggable Authentication” . This section describes how to install the test authentication plugin. For general information about installing plugins, see Section 5.6.1, “Installing and Uninstalling Plugins” . Installing Test Pluggable Authentication 1358 •Using Test Pluggable Authentication •Uninstalling Test Pluggable Authentication •Installing Test Pluggable Authentication Plugin or File Plugin or File Name Server-side plugin test_plugin_server Client-side plugin auth_test_plugin Library file auth_test_plugin.so Note 6.4.1.10 Test Pluggable Authentication CREATE USER ’valerie’@’localhost’ IDENTIFIED WITH auth_socket; ALTER USER ’valerie’@’localhost’ IDENTIFIED WITH auth_socket AS ’stephanie’; CREATE USER ’valerie’@’localhost’ IDENTIFIED WITH auth_socket AS ’stephanie’; •Name both users at account-creation time, one following  CREATE USER , and the other in the authentication string: •If you have already used  CREATE USER  to create the account for a single user, use  ALTER USER  to add the second user: