Chapter 5 Initializing the Data Directory

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

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, run mysqld as root and 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
         --basedir=/opt/mysql/mysql
         --datadir=/opt/mysql/mysql/data

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:

[mysqld]
basedir=/opt/mysql/mysql
datadir=/opt/mysql/mysql/data

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:

[mysqld]
basedir=C:\\Program Files\\MySQL\\MySQL Server 5.7
datadir=D:\\MySQLdata

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.

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:

This section describes how to initialize the data directory using mysql_install_db.

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 mysql_install_db. This program might be located under the base directory in either bin or scripts, depending on your version of MySQL. If it is in scripts, adjust the following commands appropriately.

shell> bin/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, run mysql_install_db as root and include the --user option as shown. Otherwise, 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 (prior to MySQL 5.7.4) a test database that you can use to test MySQL. The program also creates privilege table entries for the initial account or accounts. For a complete listing and description of the grant tables, see 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> bin/mysql_install_db --user=mysql \
         --basedir=/opt/mysql/mysql \
         --datadir=/opt/mysql/mysql/data

If mysql_install_db generates a random password for the root account, start the server and assign a new password:

If mysql_install_db did not generate a random password, you should still assign one. For instructions, see Securing the Initial MySQL Accounts. That section also describes how to remove the test database, if mysql_install_db created one and you do not want it.

If you have trouble with mysql_install_db at this point, see Section 5.3, “Problems Running mysql_install_db”.

The purpose of the mysql_install_db program is to initialize the data directory, including the tables in the mysql system database. It does not overwrite existing MySQL privilege tables, and it does not affect any other data.

To re-create your privilege tables, first stop the mysqld server if it is running. Then rename the mysql directory under the data directory to save it, and run mysql_install_db. Suppose that your current directory is the MySQL installation directory and that mysql_install_db is located in the bin directory and the data directory is named data. To rename the mysql database and re-run mysql_install_db, use these commands.

shell> mv data/mysql data/mysql.old
shell> bin/mysql_install_db --user=mysql

When you run mysql_install_db, you might encounter the following problems:

There are some alternatives to running the mysql_install_db program provided in the MySQL distribution: