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MySQL 8.4 Reference Manual

2.9.1 Initializing the Data Directory

After MySQL is installed, the data directory must be initialized, including the tables in themysql system schema:

For some MySQL installation methods, data directory initialization is automatic, as described inSection 2.9, “Postinstallation Setup and Testing”.
For other installation methods, you must initialize the data directory manually. These include installation from generic binary and source distributions on Unix and Unix-like systems, and installation from a ZIP Archive package on Windows.

This section describes how to initialize the data directory manually for MySQL installation methods for which data directory initialization is not automatic. For some suggested commands that enable testing whether the server is accessible and working properly, seeSection 2.9.3, “Testing the Server”.

Note

The default authentication plugin iscaching_sha2_password, and the'root'@'localhost' administrative account usescaching_sha2_password by default.

mysql_native_password (the default authentication plugin prior to MySQL 8.0) is still supported but disabled by default as of MySQL 8.4.0 and removed as of MySQL 9.0.0.

Data Directory Initialization Overview

In the examples shown here, the server is intended to run under the user ID of themysql login account. Either create the account if it does not exist (seeCreate a mysql User and Group), or substitute the name of a different existing login account that you plan to use for running the server.

Change location to the top-level directory of your MySQL installation, which is typically/usr/local/mysql (adjust the path name for your system as necessary):
```
cd /usr/local/mysql
```
Within this directory you can find several files and subdirectories, including thebin subdirectory that contains the server, as well as client and utility programs.
Thesecure_file_priv system variable limits import and export operations to a specific directory. Create a directory whose location can be specified as the value of that variable:
```
mkdir mysql-files
```
Grant directory user and group ownership to themysql user andmysql group, and set the directory permissions appropriately:
```
chown mysql:mysql mysql-fileschmod 750 mysql-files
```
Use the server to initialize the data directory, including themysql schema containing the initial MySQL grant tables that determine how users are permitted to connect to the server. For example:
```
bin/mysqld --initialize --user=mysql
```
For important information about the command, especially regarding command options you might use, seeData Directory Initialization Procedure. For details about how the server performs initialization, seeServer Actions During Data Directory Initialization.
Typically, data directory initialization need be done only after you first install MySQL. (For upgrades to an existing installation, perform the upgrade procedure instead; seeChapter 3,Upgrading MySQL.) However, the command that initializes the data directory does not overwrite any existingmysql schema tables, so it is safe to run in any circumstances.
In the absence of any option files, the server starts with its default settings. (SeeSection 7.1.2, “Server Configuration Defaults”.) To explicitly specify options that the MySQL server should use at startup, put them in an option file such as/etc/my.cnf or/etc/mysql/my.cnf. (SeeSection 6.2.2.2, “Using Option Files”.) For example, you can use an option file to set thesecure_file_priv system variable.
To arrange for MySQL to start without manual intervention at system boot time, seeSection 2.9.5, “Starting and Stopping MySQL Automatically”.
Data directory initialization creates time zone tables in themysql schema but does not populate them. To do so, use the instructions inSection 7.1.15, “MySQL Server Time Zone Support”.

Data Directory Initialization Procedure

Change location to the top-level directory of your MySQL installation, which is typically/usr/local/mysql (adjust the path name for your system as necessary):

cd /usr/local/mysql

To initialize the data directory, invokemysqld 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, or to create that account with no password:

Use--initialize for“secure by default” installation (that is, including generation of a random initialroot password). In this case, the password is marked as expired and you must choose a new one.
With--initialize-insecure, noroot password is generated. This is insecure; it is assumed that you intend to assign a password to the account in a timely fashion before putting the server into production use.

For instructions on assigning a new'root'@'localhost' password, seePost-Initialization root Password Assignment.

Note

The server writes any messages (including any initial password) 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, seeSection 7.4.2, “The Error Log”.

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

On Unix and Unix-like systems, it is important for the database directories and files to be owned by themysql login account so that the server has read and write access to them when you run it later. To ensure this, startmysqld from the systemroot account and include the--user option as shown here:

bin/mysqld --initialize --user=mysqlbin/mysqld --initialize-insecure --user=mysql

Alternatively, executemysqld while logged in asmysql, in which case you can omit the--user option from the command.

On Windows, use one of these commands:

bin\mysqld --initialize --consolebin\mysqld --initialize-insecure --console

Note

Data directory initialization might fail if required system libraries are missing. For example, you might see an error like this:

bin/mysqld: error while loading shared libraries:libnuma.so.1: cannot open shared object file:No such file or directory

If this happens, you must install the missing libraries manually or with your system's package manager. Then retry the data directory initialization command.

It might be necessary to specify other options such as--basedir or--datadir ifmysqld cannot identify the correct locations for the installation directory or data directory. For example (enter the command on a single line):

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 tomysqld. 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/mysqldatadir=/opt/mysql/mysql/data

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

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

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

[mysqld]basedir=C:\\Program Files\\MySQL\\MySQL Server 8.4datadir=D:\\MySQLdata

Then invokemysqld as follows (again, you should enter the command on a single line, with the--defaults-file option first):

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

Important

When initializing the data directory, you should not specify any options other than those used for setting directory locations such as--basedir or--datadir, and the--user option if needed. Options to be employed by the MySQL server during normal use can be set when restarting it following initialization. See the description of the--initialize option for further information.

Server Actions During Data Directory Initialization

Note

The data directory initialization sequence performed by the server does not substitute for the actions performed bymysql_secure_installation.

When invoked with the--initialize or--initialize-insecure option,mysqld performs the following actions during the data directory initialization sequence:

The server checks for the existence of the data directory as follows:
- If no data directory exists, the server creates it.
- If the data directory exists but 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.
  An existing data directory is permitted to be nonempty if every entry has a name that begins with a period (.).
Within the data directory, the server creates themysql system schema and its tables, including the data dictionary tables, grant tables, time zone tables, and server-side help tables. SeeSection 7.3, “The mysql System Schema”.
The server initializes thesystem tablespace and related data structures needed to manageInnoDB tables.
Note
Aftermysqld sets up theInnoDBsystem tablespace, certain changes to tablespace characteristics require setting up a whole newinstance. Qualifying changes include 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 theinnodb_data_file_path andinnodb_log_file_size configuration parameters are in place in the MySQLconfiguration filebefore runningmysqld. Also make sure to specify as necessary other parameters that affect the creation and location ofInnoDB files, such asinnodb_data_home_dir andinnodb_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 runmysqld.
The server creates a'root'@'localhost' superuser account and other reserved accounts (seeSection 8.2.9, “Reserved Accounts”). Some reserved accounts are locked and cannot be used by clients, but'root'@'localhost' is intended for administrative use and you should assign it a password.
Server actions with respect to a password for the'root'@'localhost' account depend 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:iTag*AfrH5ej
```
- 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 ! Pleaseconsider switching off the --initialize-insecure option.
```
For instructions on assigning a new'root'@'localhost' password, seePost-Initialization root Password Assignment.
The server populates the server-side help tables used for theHELP statement (seeSection 15.8.3, “HELP Statement”). The server does not populate the time zone tables. To do so manually, seeSection 7.1.15, “MySQL Server Time Zone Support”.
If theinit_file system variable 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 asCREATE USER orGRANT), replication, and global transaction identifiers.
The server exits.

Post-Initialization root Password Assignment

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:

Start the server. For instructions, seeSection 2.9.2, “Starting the Server”.
Connect to the server:
- If you used--initialize but not--initialize-insecure to initialize the data directory, connect to the server asroot:
```
mysql -u root -p
```
  Then, at the password prompt, enter the random password that the server generated during the initialization sequence:
```
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 asroot without a password:
```
mysql -u root --skip-password
```
After connecting, use anALTER USER statement to assign a newroot password:
```
ALTER USER 'root'@'localhost' IDENTIFIED BY 'root-password';
```

Note

Attempts to connect to the host127.0.0.1 normally resolve to thelocalhost account. However, this fails if the server is run withskip_name_resolve enabled. If you plan to do that, make sure that an account exists that can accept a connection. For example, to be able to connect asroot using--host=127.0.0.1 or--host=::1, create these accounts:

CREATE USER 'root'@'127.0.0.1' IDENTIFIED BY 'root-password';CREATE USER 'root'@'::1' IDENTIFIED BY 'root-password';

It is possible to put those statements in a file to be executed using theinit_file system variable, as discussed inServer Actions During Data Directory Initialization.

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