Chapter 5 Initializing the Data Directory
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Chapter 5 Initializing the Data Directory

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5.1 Problems Running mysql_install_db

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 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 Windows Postinstallation Procedures.) For some suggested commands that you can use to test whether the server is accessible and working properly, see 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 Chapter 1, Installing MySQL on Unix/Linux Using Generic Binaries.

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, /usr/local, or /usr/bin (for installation wtih MySQL Yum repository, or other means). 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.
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 .
```
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 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 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 \
         --datadir=/opt/mysql/mysql/data
```
For a more secure installation, invoke mysql_install_db with the --random-passwords option. This causes it to assign a random password to the MySQL root accounts, set the “password expired” flag for those accounts, and remove the anonymous-user MySQL accounts. For additional details, see mysql_install_db — Initialize MySQL Data Directory. (Install operations using RPMs for Unbreakable Linux Network are unaffected because they do not use mysql_install_db.)
If you do not want to have the test database, you can remove it after starting the server, using the instructions in Securing the Initial MySQL Accounts.
If you have trouble with mysql_install_db at this point, see Section 5.1, “Problems Running mysql_install_db”.
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.
To specify options that the MySQL server should use at startup, put them in a /etc/my.cnf or /etc/mysql/my.cnf file. See Server Configuration Defaults. If you do not do this, the server starts with its default settings.
If you want MySQL to start automatically when you boot your machine, see 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 MySQL Server Time Zone Support.

5.1 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> scripts/mysql_install_db --user=mysql

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

mysql_install_db fails to install the grant tables
You may find that mysql_install_db fails to install the grant tables and terminates after displaying the following messages:
```
Starting mysqld daemon with databases from XXXXXX
mysqld ended
```
In this case, you should examine the error log file very carefully. The log should be located in the directory XXXXXX named by the error message and should indicate why mysqld did not start. If you do not understand what happened, include the log when you post a bug report. See How to Report Bugs or Problems.
There is a mysqld process running
This indicates that the server is running, in which case the grant tables have probably been created already. If so, there is no need to run mysql_install_db at all because it needs to be run only once, when you first install MySQL.
Installing a second mysqld server does not work when one server is running
This can happen when you have an existing MySQL installation, but want to put a new installation in a different location. For example, you might have a production installation, but you want to create a second installation for testing purposes. Generally the problem that occurs when you try to run a second server is that it tries to use a network interface that is in use by the first server. In this case, you should see one of the following error messages:
```
Can't start server: Bind on TCP/IP port:
Address already in use
Can't start server: Bind on unix socket...
```
For instructions on setting up multiple servers, see Running Multiple MySQL Instances on One Machine.
You do not have write access to the /tmp directory
If you do not have write access to create temporary files or a Unix socket file in the default location (the /tmp directory) or the TMPDIR environment variable, if it has been set, an error occurs when you run mysql_install_db or the mysqld server.
You can specify different locations for the temporary directory and Unix socket file by executing these commands prior to starting mysql_install_db or mysqld, where some_tmp_dir is the full path name to some directory for which you have write permission:
```
shell> TMPDIR=/some_tmp_dir/
shell> MYSQL_UNIX_PORT=/some_tmp_dir/mysql.sock
shell> export TMPDIR MYSQL_UNIX_PORT
```
Then you should be able to run mysql_install_db and start the server with these commands:
```
shell> scripts/mysql_install_db --user=mysql
shell> bin/mysqld_safe --user=mysql &
```
If mysql_install_db is located in the scripts directory, modify the first command to scripts/mysql_install_db.
See How to Protect or Change the MySQL Unix Socket File, and Environment Variables.

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

If you want the initial privileges to be different from the standard defaults, use account-management statements such as CREATE USER, GRANT, and REVOKE to change the privileges after the grant tables have been set up. In other words, run mysql_install_db, and then use mysql -u root mysql to connect to the server as the MySQL root user so that you can issue the necessary statements. (See Account Management Statements.)
To install MySQL on several machines with the same privileges, put the CREATE USER, GRANT, and REVOKE statements in a file and execute the file as a script using mysql after running mysql_install_db. For example:
```
shell> scripts/mysql_install_db --user=mysql
shell> bin/mysql -u root < your_script_file
```
This enables you to avoid issuing the statements manually on each machine.
It is possible to re-create the grant tables completely after they have previously been created. You might want to do this if you are just learning how to use CREATE USER, GRANT, and REVOKE and have made so many modifications after running mysql_install_db that you want to wipe out the tables and start over.
To re-create the grant tables, stop the server if it is running and remove the mysql database directory. Then run mysql_install_db again.

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