MySQL stores accounts in the
user table of the
mysql system database. An account is defined in
terms of a user name and the client host or hosts from which the
user can connect to the server. For information about account
representation in the
user table, see
Section 4.3, “Grant Tables”.
An account may also have authentication credentials such as a password. The credentials are handled by the account authentication plugin. MySQL supports multiple authentication plugins. Some of them use built-in authentication methods, whereas others enable authentication using external authentication methods. See Section 4.10, “Pluggable Authentication”.
There are several distinctions between the way user names and passwords are used by MySQL and your operating system:
User names, as used by MySQL for authentication purposes, have nothing to do with user names (login names) as used by Windows or Unix. On Unix, most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only. The default can be overridden easily, because client programs permit any user name to be specified with a
--useroption. This means that anyone can attempt to connect to the server using any user name, so you cannot make a database secure in any way unless all MySQL accounts have passwords. Anyone who specifies a user name for an account that has no password can connect successfully to the server.
MySQL user names are up to 16 characters long. Operating system user names may have a different maximum length.Warning
The MySQL user name length limit is hardcoded in MySQL servers and clients, and trying to circumvent it by modifying the definitions of the tables in the
mysqldatabase does not work.
You should never alter the structure of tables in the
mysqldatabase in any manner whatsoever except by means of the procedure that is described in Upgrading MySQL. Attempting to redefine MySQL's system tables in any other fashion results in undefined and unsupported behavior. The server is free to ignore rows that become malformed as a result of such modifications.
To authenticate client connections for accounts that use built-in authentication methods, the server uses passwords stored in the
usertable. These passwords are distinct from passwords for logging in to your operating system. There is no necessary connection between the “external” password you use to log in to a Windows or Unix machine and the password you use to access the MySQL server on that machine.
If the server authenticates a client using some other plugin, the authentication method that the plugin implements may or may not use a password stored in the
usertable. In this case, it is possible that an external password is also used to authenticate to the MySQL server.
Passwords stored in the
usertable are encrypted using plugin-specific algorithms. For information about MySQL native password hashing, see Section 2.2.4, “Password Hashing in MySQL”.
If the user name and password contain only ASCII characters, it is possible to connect to the server regardless of character set settings. To enable connections when the user name or password contain non-ASCII characters, client applications should call the
mysql_options()C API function with the
MYSQL_SET_CHARSET_NAMEoption and appropriate character set name as arguments. This causes authentication to take place using the specified character set. Otherwise, authentication fails unless the server default character set is the same as the encoding in the authentication defaults.
Standard MySQL client programs support a
--default-character-setoption that causes
mysql_options()to be called as just described. In addition, character set autodetection is supported as described in Connection Character Sets and Collations. For programs that use a connector that is not based on the C API, the connector may provide an equivalent to
mysql_options()that can be used instead. Check the connector documentation.
The preceding notes do not apply for
utf32, which are not permitted as client character sets.
The MySQL installation process populates the grant tables with an
initial account or accounts. The names and access privileges for
these accounts are described in
Section 3.4, “Securing the Initial MySQL Accounts”, which also discusses how to
assign passwords to them. Thereafter, you normally set up, modify,
and remove MySQL accounts using statements such as
Section 4.7, “Adding Accounts, Assigning Privileges, and Dropping Accounts”, and
Account Management Statements.
To connect to a MySQL server with a command-line client, specify user name and password options as necessary for the account that you want to use:
shell> mysql --user=finley --password db_name
If you prefer short options, the command looks like this:
shell> mysql -u finley -p db_name
If you omit the password value following the
option on the command line (as just shown), the client prompts for
one. Alternatively, the password can be specified on the command
shell> mysql --user=finley --password=password db_name shell> mysql -u finley -ppassword db_name
If you use the
-p option, there must be
no space between
-p and the
following password value.
Specifying a password on the command line should be considered insecure. See Section 2.2.1, “End-User Guidelines for Password Security”. To avoid giving the password on the command line, use an option file. See Using Option Files.
For additional information about specifying user names, passwords, and other connection parameters, see Connecting to the MySQL Server.