5.2 The MySQL Data Directory

Information managed by the MySQL server is stored under a directory known as the data directory. The following list briefly describes the items typically found in the data directory, with cross references for additional information:

• Data directory subdirectories. Each subdirectory of the data directory is a database directory and corresponds to a database managed by the server. All MySQL installations have certain standard databases:

  • The mysql directory corresponds to the mysql system schema, which contains information required by the MySQL server as it runs. This database contains data dictionary tables and system tables. See Section 5.3, “The mysql System Schema”.

  • The performance_schema directory corresponds to the Performance Schema, which provides information used to inspect the internal execution of the server at runtime. See Chapter 27, MySQL Performance Schema.

  • The sys directory corresponds to the sys schema, which provides a set of objects to help interpret Performance Schema information more easily. See Chapter 28, MySQL sys Schema.

  • The ndbinfo directory corresponds to the ndbinfo database that stores information specific to NDB Cluster (present only for installations built to include NDB Cluster). See Section 23.6.16, “ndbinfo: The NDB Cluster Information Database”.

  Other subdirectories correspond to databases created by users or applications.

  Note

  INFORMATION_SCHEMA is a standard database, but its implementation uses no corresponding database directory.

• Log files written by the server. See Section 5.4, “MySQL Server Logs”.

• InnoDB tablespace and log files. See Chapter 15, The InnoDB Storage Engine.

• Default/autogenerated SSL and RSA certificate and key files. See Section 6.3.3, “Creating SSL and RSA Certificates and Keys”.

• The server process ID file (while the server is running).

• The mysqld-auto.cnf file that stores persisted global system variable settings. See Section 13.7.6.1, “SET Syntax for Variable Assignment”.

Some items in the preceding list can be relocated elsewhere by reconfiguring the server. In addition, the --datadir option enables the location of the data directory itself to be changed. For a given MySQL installation, check the server configuration to determine whether items have been moved.