Environment Variables This section lists environment variables that are used directly or indirectly by MySQL. Most of these can also be found in other places in this manual. Options on the command line take precedence over values specified in option files and environment variables, and values in option files take precedence over values in environment variables. In many cases, it is preferable to use an option file instead of environment variables to modify the behavior of MySQL. See Section 4.2.2.2, “Using Option Files” . Variable Description AUTHENTICATION_LDAP_CLIENT_LOG Client-side LDAP authentication logging level. AUTHENTICATION_PAM_LOG PAM authentication plugin debug logging settings. CC The name of your C compiler (for running  CMake ). CXX The name of your C++ compiler (for running CMake ). CC The name of your C compiler (for running  CMake ). DBI_USER The default user name for Perl DBI. DBI_TRACE Trace options for Perl DBI. HOME The default path for the  mysql  history file is $HOME/.mysql_history . LD_RUN_PATH Used to specify the location of libmysqlclient.so . LIBMYSQL_ENABLE_CLEARTEXT_PLUGIN Enable  mysql_clear_password  authentication plugin; see Section 6.4.1.4, “Client-Side Cleartext Pluggable Authentication” . LIBMYSQL_PLUGIN_DIR Directory in which to look for client plugins. LIBMYSQL_PLUGINS Client plugins to preload. MYSQL_DEBUG Debug trace options when debugging. MYSQL_GROUP_SUFFIX Option group suffix value (like specifying  -- defaults-group-suffix ). MYSQL_HISTFILE The path to the  mysql  history file. If this variable is set, its value overrides the default for $HOME/.mysql_history . MYSQL_HISTIGNORE Patterns specifying statements that  mysql  should not log to  $HOME/.mysql_history , or  syslog  if --syslog  is given. MYSQL_HOME The path to the directory in which the server-specific my.cnf  file resides. MYSQL_HOST The default host name used by the  mysql command-line client. MYSQL_OPENSSL_UDF_DH_BITS_THRESHOLD Maximum key length for create_dh_parameters() . See Section 6.6.2, “MySQL Enterprise Encryption Usage and Examples” . MYSQL_OPENSSL_UDF_DSA_BITS_THRESHOLD Maximum DSA key length for create_asymmetric_priv_key() . See Section 6.6.2, “MySQL Enterprise Encryption Usage and Examples” . 632