Part of the MySQL installation process is to set up the mysql database that contains the grant tables:

The mysql.user grant table defines the initial MySQL user accounts and their access privileges:

To display which accounts exist in the mysql.user table and check whether their passwords are empty, use the following statement:

mysql> SELECT User, Host, Password FROM mysql.user;
+------+--------------------+----------+
| User | Host               | Password |
+------+--------------------+----------+
| root | localhost          |          |
| root | myhost.example.com |          |
|      | localhost          |          |
|      | myhost.example.com |          |
+------+--------------------+----------+

This output indicates that there are several root and anonymous-user accounts, none of which have passwords. The output might differ on your system, but the presence of accounts with empty passwords means that your MySQL installation is unprotected until you do something about it:

In addition, the mysql.db table contains rows that permit all accounts to access the test database and other databases with names that start with test (on Windows) or that start with test_ (on Unix). Access to test databases is permitted even for accounts that otherwise have no special privileges such as the default anonymous accounts. This is convenient for testing but inadvisable on production servers. Administrators who want database access restricted only to accounts that have permissions granted explicitly for that purpose should remove these mysql.db table rows.

The following instructions describe how to set up passwords for the initial MySQL accounts, first for the root accounts, then for the anonymous accounts. The instructions also cover how to remove the anonymous accounts, should you prefer not to permit anonymous access at all, and describe how to remove permissive access to test databases. Replace newpwd in the examples with the password that you want to use. Replace host_name with the name of the server host. You can determine this name from the output of the preceding SELECT statement. For the output shown, host_name is myhost.example.com.

You might want to defer setting the passwords until later, to avoid the need to specify them while you perform additional setup or testing. However, be sure to set them before using your installation for production purposes.

To set up additional accounts, see Section 5.6.2, “Adding User Accounts”.

Assigning root Account Passwords

The root account passwords can be set several ways. The following discussion demonstrates three methods:

To assign passwords using SET PASSWORD, connect to the server as root and issue a SET PASSWORD statement for each root account listed in the mysql.user table. Be sure to encrypt the password using the PASSWORD() function.

For Windows, do this:

shell> mysql -u root
mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWORD('newpwd');
mysql> SET PASSWORD FOR 'root'@'%' = PASSWORD('newpwd');

The last statement is unnecessary if the mysql.user table has no root account with a host value of %.

For Unix, do this:

shell> mysql -u root
mysql> SET PASSWORD FOR 'root'@'localhost' = PASSWORD('newpwd');
mysql> SET PASSWORD FOR 'root'@'host_name' = PASSWORD('newpwd');

You can also use a single statement that assigns a password to all root accounts by using UPDATE to modify the mysql.user table directly. This method works on any platform:

shell> mysql -u root
mysql> UPDATE mysql.user SET Password = PASSWORD('newpwd')
    ->     WHERE User = 'root';
mysql> FLUSH PRIVILEGES;

The FLUSH statement causes the server to reread the grant tables. Without it, the password change remains unnoticed by the server until you restart it.

To assign passwords to the root accounts using mysqladmin, execute the following commands:

shell> mysqladmin -u root password "newpwd"
shell> mysqladmin -u root -h host_name password "newpwd"

Those commands apply both to Windows and to Unix. The double quotation marks around the password are not always necessary, but you should use them if the password contains spaces or other characters that are special to your command interpreter.

If you are using a server from a very old version of MySQL, the mysqladmin commands to set the password fail with the message parse error near 'SET password'. The solution to this problem is to upgrade the server to a newer version of MySQL.

After the root passwords have been set, you must supply the appropriate password whenever you connect as root to the server. For example, to shut down the server with mysqladmin, use this command:

shell> mysqladmin -u root -p shutdown
Enter password: (enter root password here)

Assigning Anonymous Account Passwords

The mysql commands in the following instructions include a -p option based on the assumption that you have set the root account passwords using the preceding instructions and must specify that password when connecting to the server.

To assign passwords to the anonymous accounts, connect to the server as root, then use either SET PASSWORD or UPDATE. Be sure to encrypt the password using the PASSWORD() function.

To use SET PASSWORD on Windows, do this:

shell> mysql -u root -p
Enter password: (enter root password here)
mysql> SET PASSWORD FOR ''@'localhost' = PASSWORD('newpwd');
mysql> SET PASSWORD FOR ''@'%' = PASSWORD('newpwd');

To use SET PASSWORD on Unix, do this:

shell> mysql -u root -p
Enter password: (enter root password here)
mysql> SET PASSWORD FOR ''@'localhost' = PASSWORD('newpwd');
mysql> SET PASSWORD FOR ''@'host_name' = PASSWORD('newpwd');

To set the anonymous-user account passwords with UPDATE, do this (on any platform):

shell> mysql -u root -p
Enter password: (enter root password here)
mysql> UPDATE mysql.user SET Password = PASSWORD('newpwd')
    ->     WHERE User = '';
mysql> FLUSH PRIVILEGES;

The FLUSH statement causes the server to reread the grant tables. Without it, the password change remains unnoticed by the server until you restart it.

Removing Anonymous Accounts

If you prefer to remove any anonymous accounts rather than assigning them passwords, do so as follows:

shell> mysql -u root -p
Enter password: (enter root password here)
mysql> DELETE FROM mysql.user WHERE User = '';
mysql> FLUSH PRIVILEGES;

The DELETE statement applies both to Windows and to Unix. On Windows, if you want to remove only the anonymous account that has the same privileges as root, do this instead:

shell> mysql -u root -p
Enter password: (enter root password here)
mysql> DELETE FROM mysql.user WHERE Host='localhost' AND User='';
mysql> FLUSH PRIVILEGES;

That account permits anonymous access but has full privileges, so removing it improves security.

Securing Test Databases

By default, the mysql.db table contains rows that permit access by any user to the test database and other databases with names that start with test_. (These rows have an empty User column value, which for access-checking purposes matches any user name.) This means that such databases can be used even by accounts that otherwise possess no privileges. If you want to remove any-user access to test databases, do so as follows:

shell> mysql -u root -p
Enter password: (enter root password here)
mysql> DELETE FROM mysql.db WHERE Db LIKE 'test%';
mysql> FLUSH PRIVILEGES;

The FLUSH statement causes the server to reread the grant tables. Without it, the privilege change remains unnoticed by the server until you restart it.

With the preceding change, only users who have global database privileges or privileges granted explicitly for the test database can use it. However, if you do not want the database to exist at all, drop it:

mysql> DROP DATABASE test;