Authentication Plugins ON ’proxied_user’@’localhost’ TO ’proxy_user’@’localhost’; This enables clients to access MySQL through the proxy account ( proxy_user ) but not to bypass the proxy mechanism by connecting directly as the proxied user ( proxied_user ). A client who connects using the  proxy_user  account has the privileges of the  proxied_user  account, but  proxied_user itself cannot be used to connect. For alternative methods of protecting proxied accounts against direct use, see Preventing Direct Login to Proxied Accounts. The server-side  auth_socket  authentication plugin authenticates clients that connect from the local host through the Unix socket file. The plugin uses the  SO_PEERCRED  socket option to obtain information about the user running the client program. Thus, the plugin can be used only on systems that support the SO_PEERCRED  option, such as Linux. The source code for this plugin can be examined as a relatively simple example demonstrating how to write a loadable authentication plugin. The following table shows the plugin and library file names. The file must be located in the directory named by the  plugin_dir  system variable. The following sections provide installation and usage information specific to socket pluggable authentication: For general information about pluggable authentication in MySQL, see Section 6.2.17, “Pluggable Authentication” . This section describes how to install the socket authentication plugin. For general information about installing plugins, see Section 5.6.1, “Installing and Uninstalling Plugins” . To be usable by the server, the plugin library file must be located in the MySQL plugin directory (the directory named by the  plugin_dir  system variable). If necessary, configure the plugin directory location by setting the value of  plugin_dir  at server startup. To load the plugin at server startup, use the  --plugin-load-add  option to name the library file that contains it. With this plugin-loading method, the option must be given each time the server starts. For example, put these lines in the server  my.cnf  file: 1356 Installing Socket Pluggable Authentication [mysqld] Table 6.21 Plugin and Library Names for Socket Peer-Credential Authentication •Using Socket Pluggable Authentication •Uninstalling Socket Pluggable Authentication •Installing Socket Pluggable Authentication Plugin or File Plugin or File Name Server-side plugin auth_socket Client-side plugin None, see discussion Library file auth_socket.so 6.4.1.9 Socket Peer-Credential Pluggable Authentication