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MySQL 5.7 Reference Manual  /  ...  /  Initializing the Data Directory Manually Using mysqld Initializing the Data Directory Manually Using mysqld

This section describes how to initialize the data directory using mysqld, the MySQL server.


The procedure described here is available for all platforms as of MySQL 5.7.6. Prior to 5.7.6, use mysql_install_db on Unix and Unix-like systems (see Section, “Initializing the Data Directory Manually Using mysql_install_db”). Prior to MySQL 5.7.7, Windows distributions include a data directory with prebuilt tables in the mysql database.

The following instructions assume that your current location is the MySQL installation directory, represented here by BASEDIR:

shell> cd BASEDIR

To initialize the data directory, invoke mysqld with the --initialize or --initialize-insecure option, depending on whether you want the server to generate a random initial password for the 'root'@'localhost' account.

On Windows, use one of these commands:

C:\> bin\mysqld --initialize
C:\> bin\mysqld --initialize-insecure

On Unix and Unix-like systems, it is important to make sure that the database directories and files are owned by the mysql login account so that the server has read and write access to them when you run it later. To ensure this if you run mysqld as root, include the --user option as shown here:

shell> bin/mysqld --initialize --user=mysql
shell> bin/mysqld --initialize-insecure --user=mysql

Otherwise, execute the program while logged in as mysql, in which case you can omit the --user option from the command.

Regardless of platform, use --initialize for secure by default installation (that is, including generation of a random initial root password). In this case, the password is marked as expired and you will need to choose a new one. With the --initialize-insecure option, no root password is generated; it is assumed that you will assign a password to the account in timely fashion before putting the server into production use.

It might be necessary to specify other options such as --basedir or --datadir if mysqld does not identify the correct locations for the installation directory or data directory. For example (enter the command on one line):

shell> bin/mysqld --initialize --user=mysql

Alternatively, put the relevant option settings in an option file and pass the name of that file to mysqld. For Unix and Unix-like systems, suppose that the option file name is /opt/mysql/mysql/etc/my.cnf. Put these lines in the file:


Then invoke mysqld as follows (enter the command on a single line with the --defaults-file option first):

shell> bin/mysqld --defaults-file=/opt/mysql/mysql/etc/my.cnf
         --initialize --user=mysql

On Windows, suppose that C:\my.ini contains these lines:

basedir=C:\\Program Files\\MySQL\\MySQL Server 5.7

Then invoke mysqld as follows (the --defaults-file option must be first):

C:\> bin/mysqld --defaults-file=C:\my.ini --initialize

When invoked with the --initialize or --initialize-insecure option, mysqld performs the following initialization sequence.


The server writes any messages to its standard error output. This may be redirected to the error log, so look there if you do not see the messages on your screen. For information about the error log, including where it is located, see Section 6.4.2, “The Error Log”.

On Windows, use the --console option to direct messages to the console.

  1. The server checks for the existence of the data directory as follows:

    • If no data directory exists, the server creates it.

    • If a data directory exists and is not empty (that is, it contains files or subdirectories), the server exits after producing an error message:

      [ERROR] --initialize specified but the data directory exists. Aborting.

      In this case, remove or rename the data directory and try again.

      As of MySQL 5.7.11, an existing data directory is permitted to be nonempty if every entry either has a name that begins with a period (.) or is named using an --ignore-db-dir option.

  2. Within the data directory, the server creates the mysql system database and its tables, including the grant tables, server-side help tables, and time zone tables. For a complete listing and description of the grant tables, see Section 7.2, “The MySQL Access Privilege System”.

  3. The server initializes the system tablespace and related data structures needed to manage InnoDB tables.


    After mysqld sets up the InnoDB system tablespace, changes to some tablespace characteristics require setting up a whole new instance. This includes the file name of the first file in the system tablespace and the number of undo logs. If you do not want to use the default values, make sure that the settings for the innodb_data_file_path and innodb_log_file_size configuration parameters are in place in the MySQL configuration file before running mysqld. Also make sure to specify as necessary other parameters that affect the creation and location of InnoDB files, such as innodb_data_home_dir and innodb_log_group_home_dir.

    If those options are in your configuration file but that file is not in a location that MySQL reads by default, specify the file location using the --defaults-extra-file option when you run mysqld.

  4. The server creates a 'root'@'localhost' superuser account. The server's action with respect to a password for this account depends on how you invoke it:

    • With --initialize but not --initialize-insecure, the server generates a random password, marks it as expired, and writes a message displaying the password:

      [Warning] A temporary password is generated for root@localhost:
    • With --initialize-insecure, (either with or without --initialize because --initialize-insecure implies --initialize), the server does not generate a password or mark it expired, and writes a warning message:

      Warning] root@localhost is created with an empty password ! Please
      consider switching off the --initialize-insecure option.
  5. The server populates the server-side help tables if content is available (in the fill_help_tables.sql file). The server does not populate the time zone tables; to do so, see Section 11.6, “MySQL Server Time Zone Support”.

  6. If the --init-file option was given to name a file of SQL statements, the server executes the statements in the file. This option enables you to perform custom bootstrapping sequences.

    When the server operates in bootstrap mode, some functionality is unavailable that limits the statements permitted in the file. These include statements that relate to account management (such as CREATE USER or GRANT), replication, and global transaction identifiers.

  7. The server exits.

After you initialize the data directory by starting the server with --initialize or --initialize-insecure, start the server normally (that is, without either of those options) and assign the 'root'@'localhost' account a new password:

  1. Start the server. For instructions, see Section 2.10.2, “Starting the Server”.

  2. Connect to the server:

    • If you used --initialize but not --initialize-insecure to initialize the data directory, connect to the server as root using the random password that the server generated during the initialization sequence:

      shell> mysql -u root -p
      Enter password: (enter the random root password here)

      Look in the server error log if you do not know this password.

    • If you used --initialize-insecure to initialize the data directory, connect to the server as root without a password:

      shell> mysql -u root --skip-password
  3. After connecting, assign a new root password:

    mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'new_password';

The data directory initialization sequence performed by the server does not substitute for the actions performed by mysql_secure_installation or mysql_ssl_rsa_setup. See Section 5.4.4, “mysql_secure_installation — Improve MySQL Installation Security”, and Section 5.4.5, “mysql_ssl_rsa_setup — Create SSL/RSA Files”.

User Comments
  Posted by Ilguiz Latypov on May 10, 2016
I missed the my.cnf / my.ini encoding rule that interprets the back-slash character as an escape character.

It would make sense to emphasize this in my-default.ini, along with a suggestion to use forward-slashes instead of doubling back-slashes.
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