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MySQL 5.5 Reference Manual
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2.10.1 Initializing the Data Directory

After installing MySQL, you must initialize the data directory, including the tables in the mysql system database. For some MySQL installation methods, data directory initialization may be done automatically, as described in Section 2.10, “Postinstallation Setup and Testing”. For other installation methods, including installation from generic binary and source distributions, you must initialize the data directory yourself.

This section describes how to initialize the data directory on Unix and Unix-like systems. (For Windows, see Section 2.3.9, “Windows Postinstallation Procedures”.) For some suggested commands that you can use to test whether the server is accessible and working properly, see Section 2.10.3, “Testing the Server”.

In the examples shown here, the server runs under the user ID of the mysql login account. This assumes that such an account exists. Either create the account if it does not exist, or substitute the name of a different existing login account that you plan to use for running the server. For information about creating the account, see Creating a mysql System User and Group, in Section 2.2, “Installing MySQL on Unix/Linux Using Generic Binaries”.

  1. Change location into the top-level directory of your MySQL installation, represented here by BASEDIR:

    shell> cd BASEDIR

    BASEDIR is likely to be something like /usr/local/mysql or /usr/local. The following steps assume that you have changed location to this directory.

    You will find several files and subdirectories in the BASEDIR directory. The most important for installation purposes are the bin and scripts subdirectories, which contain the server as well as client and utility programs.

  2. If necessary, ensure that the distribution contents are accessible to mysql. If you installed the distribution as mysql, no further action is required. If you installed the distribution as root, its contents will be owned by root. Change its ownership to mysql by executing the following commands as root in the installation directory. The first command changes the owner attribute of the files to the mysql user. The second changes the group attribute to the mysql group.

    shell> chown -R mysql .
    shell> chgrp -R mysql .
  3. If necessary, initialize the data directory, including the mysql database containing the initial MySQL grant tables that determine how users are permitted to connect to the server.

    Typically, data directory initialization need be done only the first time you install MySQL. If you are upgrading an existing installation, you should run mysql_upgrade instead (see Section 4.4.7, “mysql_upgrade — Check and Upgrade MySQL Tables”). However, the command that initializes the data directory does not overwrite any existing privilege tables, so it should be safe to run in any circumstances.

    shell> scripts/mysql_install_db --user=mysql

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

    The mysql_install_db command creates the server's data directory. Under the data directory, it creates directories for the mysql database that holds the grant tables and the test database that you can use to test MySQL. The program also creates privilege table entries for the initial account or accounts. test_. For a complete listing and description of the grant tables, see Section 6.2, “The MySQL Access Privilege System”.

    It might be necessary to specify other options such as --basedir or --datadir if mysql_install_db does not identify the correct locations for the installation directory or data directory. For example:

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

    If you do not want to have the test database, you can remove it after starting the server, using the instructions in Section 2.10.4, “Securing the Initial MySQL Accounts”.

    If you have trouble with mysql_install_db at this point, see Section, “Problems Running mysql_install_db”.

  4. After initializing the data directory, you can establish the final installation ownership settings. To leave the installation owned by mysql, no action is required here. Otherwise, most of the MySQL installation can be owned by root if you like. The exception is that the data directory must be owned by mysql. To accomplish this, run the following commands as root in the installation directory. For some distribution types, the data directory might be named var rather than data; adjust the second command accordingly.

    shell> chown -R root .
    shell> chown -R mysql data

    If the plugin directory (the directory named by the plugin_dir system variable) is writable by the server, it may be possible for a user to write executable code to a file in the directory using SELECT ... INTO DUMPFILE. This can be prevented by making the plugin directory read only to the server or by setting the secure_file_priv system variable at server startup to a directory where SELECT writes can be performed safely.

  5. If you installed MySQL using a source distribution, you may want to optionally copy one of the provided configuration files from the support-files directory into your /etc directory. There are different sample configuration files for different use cases, server types, and CPU and RAM configurations. To use one of these standard files, copy it to /etc/my.cnf, or /etc/mysql/my.cnf and edit and check the configuration before starting your MySQL server for the first time.

    You can also create my.cnf yourself and place into it the options the server should use at startup. See Section 5.1.2, “Server Configuration Defaults”.

    If you do not copy one of the standard configuration files or create your own, the MySQL server starts with its default settings.

  6. If you want MySQL to start automatically when you boot your machine, see Section 2.10.5, “Starting and Stopping MySQL Automatically”.

Data directory initialization creates time zone tables in the mysql database but does not populate them. To do so, use the instructions in Section 5.1.12, “MySQL Server Time Zone Support”.

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