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 4.2, “Privilege System Grant Tables”.
The account may also have a password. MySQL supports authentication plugins, so it is possible that an account authenticates using some external authentication method. See Section 5.6, “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
--user option. 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 is able to connect
successfully to the server.
MySQL user names can be up to 16 characters long. Operating system user names may be of a different maximum length. For example, Unix user names typically are limited to eight characters.
The limit on MySQL user name length is hard-coded in MySQL
servers and clients, and trying to circumvent it by
modifying the definitions of the tables in the
mysql database does not
You should never alter the structure of tables in the
mysql database in any manner whatsoever
except by means of the procedure that is described in
mysql_upgrade — Check and Upgrade MySQL Tables. 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
To authenticate client connections for accounts that use MySQL
native authentication (implemented by the
plugin), the server uses passwords stored in the
user table. 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
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
table. In this case, it is possible that an external password
is also used to authenticate to the MySQL server.
Passwords stored in the
user table 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 connect when the user name or
password contain non-ASCII characters, the client should call
mysql_options() C API
function with the
option and appropriate character set name as arguments. This
causes authentication to take place using the specified
character set. Otherwise, authentication will fail unless the
server default character set is the same as the encoding in
the authentication defaults.
Standard MySQL client programs support a
--default-character-set option 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
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
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:
mysql --user=monty --password
If you prefer short options, the command looks like this:
mysql -u monty -p
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
mysql --user=monty --password=shell>
mysql -u monty -p
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”. You can use an option file to avoid giving the password on the command line. See Using Option Files.
For additional information about specifying user names, passwords, and other connection parameters, see Connecting to the MySQL Server.