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MySQL 5.6 Reference Manual  /  ...  /  mysql_install_db — Initialize MySQL Data Directory

4.4.3 mysql_install_db — Initialize MySQL Data Directory

mysql_install_db initializes the MySQL data directory and creates the system tables that it contains, if they do not exist. It also initializes the system tablespace and related data structures needed to manage InnoDB tables. As of MySQL 5.6.8, mysql_install_db is a Perl script and can be used on any system with Perl installed. Before 5.6.8, it is a shell script and is available only on Unix platforms.

As of MySQL 5.6.8, on Unix platforms, mysql_install_db creates a default option file named my.cnf in the base installation directory. This file is created from a template included in the distribution package named my-default.cnf. You can find the template in or under the base installation directory. When started using mysqld_safe, the server uses my.cnf file by default. If my.cnf already exists, mysql_install_db assumes it to be in use and writes a new file named my-new.cnf instead.

With one exception, the settings in the default option file are commented and have no effect. The exception is that the file sets the sql_mode system variable to NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES. This setting produces a server configuration that results in errors rather than warnings for bad data in operations that modify transactional tables. See Section 5.1.10, “Server SQL Modes”.

To invoke mysql_install_db, use the following syntax:

mysql_install_db [options]

Because the MySQL server, mysqld, must access the data directory when it runs later, you should either run mysql_install_db from the same system account that is used for running mysqld, or run it as root and specify the --user option to indicate the user name that mysqld runs as. It might be necessary to specify other options such as --basedir or --datadir if mysql_install_db does not use the correct locations for the installation directory or data directory. For example:

scripts/mysql_install_db --user=mysql \
    --basedir=/opt/mysql/mysql \

After mysql_install_db 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 mysql_install_db. 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 mysql_install_db.


If you have set a custom TMPDIR environment variable when performing the installation, and the specified directory is not accessible, mysql_install_db may fail. If so, unset TMPDIR or set TMPDIR to point to the system temporary directory (usually /tmp).

mysql_install_db supports the following options, which can be specified on the command line or in the [mysql_install_db] group of an option file. (Options that are common to mysqld can also be specified in the [mysqld] group.) Other options are passed to mysqld. For information about option files used by MySQL programs, see Section, “Using Option Files”.

Table 4.7 mysql_install_db Options

Option Name Description Introduced Deprecated
--basedir Path to base directory
--builddir Path to build directory (for out-of-source builds)
--cross-bootstrap For internal use
--datadir Path to data directory
--defaults-extra-file Read named option file in addition to usual option files
--defaults-file Read only named option file
--force Run even if DNS does not work
--help Display help message and exit
--keep-my-cnf Keep existing my.cnf file, do not create new one 5.6.20 5.6.20
--ldata Synonym for --datadir
--no-defaults Read no option files
--random-passwords Generate administrative account random password
--rpm For internal use
--skip-name-resolve Use IP addresses rather than host names in grant tables
--srcdir For internal use
--user Operating system user under which to execute mysqld
--verbose Verbose mode
--windows For internal use

  • --help

    Display a help message and exit.

  • --basedir=dir_name

    The path to the MySQL installation directory.

  • --builddir=dir_name

    For use with --srcdir and out-of-source builds. Set this to the location of the directory where the built files reside.

  • --cross-bootstrap

    For internal use. This option is used for building system tables on one host intended for another.

  • --datadir=dir_name

    The path to the MySQL data directory. Beginning with MySQL 5.6.8, mysql_install_db is more strict about the option value. Only the last component of the path name is created if it does not exist; the parent directory must already exist or an error occurs.

  • --defaults-extra-file=file_name

    Read this option file after the global option file but (on Unix) before the user option file. If the file does not exist or is otherwise inaccessible, an error occurs. If file_name is not an absolute path name, it is interpreted relative to the current directory.

    For additional information about this and other option-file options, see Section, “Command-Line Options that Affect Option-File Handling”.

  • --defaults-file=file_name

    Use only the given option file. If the file does not exist or is otherwise inaccessible, an error occurs. If file_name is not an absolute path name, it is interpreted relative to the current directory.

    For additional information about this and other option-file options, see Section, “Command-Line Options that Affect Option-File Handling”.

  • --force

    Cause mysql_install_db to run even if DNS does not work. Grant table entries normally created using host names use IP addresses instead.

  • --keep-my-cnf

    Tell mysql_install_db to preserve any existing my.cnf file and not create a new default my.cnf file. This option was added in MySQL 5.6.20.

  • --ldata=dir_name

    A synonym for --datadir.

  • --no-defaults

    Do not read any option files. If program startup fails due to reading unknown options from an option file, --no-defaults can be used to prevent them from being read.

    For additional information about this and other option-file options, see Section, “Command-Line Options that Affect Option-File Handling”.

  • --random-passwords

    On Unix platforms, this option provides for more secure MySQL installation. Invoking mysql_install_db with --random-passwords causes it to perform the following actions in addition to its normal operation:

    • The installation process creates a random password, assigns it to the initial MySQL root accounts, and sets the password expired flag for those accounts.

    • The initial random root password is written to the .mysql_secret file in the directory named by the HOME environment variable. Depending on operating system, using a command such as sudo may cause the value of HOME to refer to the home directory of the root system user.

      If .mysql_secret already exists, the new password information is appended to it. Each password entry includes a timestamp so that in the event of multiple install operations it is possible to determine the password associated with each one.

      .mysql_secret is created with mode 600 to be accessible only to the operating system user for whom it is created.

    • No anonymous-user MySQL accounts are created.

    As a result of these actions, it is necessary after installation to start the server, connect as root using the password written to the .mysql_secret file, and specify a new root password. Until this is done, root cannot do anything else. This must be done for each root account you intend to use. To change the password, you can use the SET PASSWORD statement (for example, with the mysql client). You can also use mysqladmin or mysql_secure_installation.

    New RPM install operations (not upgrades) invoke mysql_install_db with the --random-passwords option. (Install operations using RPMs for Unbreakable Linux Network are unaffected because they do not use mysql_install_db.)

    As of MySQL 5.6.9, new Solaris PKG install operations (not upgrades) invoke mysql_install_db with the --random-passwords option.

    For install operations using a binary .tar.gz distribution or a source distribution, you can invoke mysql_install_db with the --random-passwords option manually to make your MySQL installation more secure. This is recommended, particularly for sites with sensitive data.

  • --rpm

    For internal use. This option is used during the MySQL installation process for install operations performed using RPM packages.

  • --skip-name-resolve

    Use IP addresses rather than host names when creating grant table entries. This option can be useful if your DNS does not work.

  • --srcdir=dir_name

    For internal use. This option specifies the directory under which mysql_install_db looks for support files such as the error message file and the file for populating the help tables.

  • --user=user_name

    The system (login) user name to use for running mysqld. Files and directories created by mysqld are owned by this user. You must be the system root user to use this option. By default, mysqld runs using your current login name and files and directories that it creates are owned by you.

  • --verbose

    Verbose mode. Print more information about what the program does.

  • --windows

    For internal use. This option is used for creating Windows distributions.