MySQL stores accounts in the
user table of the
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. The account may also have a password. For information about account representation in the
user table, see Section 6.2.2,
"Privilege System Grant Tables". MySQL 5.7 supports authentication plugins, so it is possible that an
account authenticates using some external authentication method. See Section
6.3.7, "Pluggable Authentication".
There are several distinctions between the way user names and passwords are used by MySQL and the way they are used by 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. Because this means that
anyone can attempt to connect to the server using any user name, 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, because they are completely unrelated to MySQL 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 the MySQL servers and clients, and
trying to circumvent it by modifying the definitions of the tables in the
database does not work.
You should never alter any of the tables in the
database in any manner whatsoever except by means of the procedure that is described in Section 4.4.7, "mysql_upgrade — Check and Upgrade MySQL Tables".
Attempting to redefine MySQL's system tables in any other fashion results in undefined (and
The server uses MySQL passwords stored in the
table to authenticate client connections using MySQL native authentication (against passwords stored in
mysql.user table). These passwords have nothing to do with 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 a plugin, the authentication method that the plugin
implements may or may not use the password in the
user table. In this
case, it is possible that an external password is also used to authenticate to the MySQL server.
MySQL encrypts passwords stored in the
using its own algorithm. This encryption is the same as that implemented by the
PASSWORD() SQL function but differs from that used during the Unix
login process. Unix password encryption is the same as that implemented by the
ENCRYPT() SQL function. See the descriptions of the
ENCRYPT() functions in Section
12.13, "Encryption and Compression Functions".
From version 4.1 on, MySQL employs a stronger authentication method that has better password
protection during the connection process than in earlier versions. It is secure even if TCP/IP
packets are sniffed or the
mysql database is captured. (In earlier
versions, even though passwords are stored in encrypted form in the
user table, knowledge of the encrypted password value could be used
to connect to the MySQL server.) Section 22.214.171.124,
"Password Hashing in MySQL", discusses password encryption further.
It is possible to connect to the server regardless of character set settings if the
user name and password contain only ASCII characters. To connect when the user name or password contain
non-ASCII characters, the client should call the
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
to be called as just described. In addition, character set autodetection is supported as described
in Section 10.1.4, "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
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.
When you install MySQL, the grant tables are populated with an initial set of accounts. The names and access
privileges for these accounts are described in Section
2.10.2, "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
REVOKE. See Section 13.7.1,
"Account Management Statements".
When you connect to a MySQL server with a command-line client, specify the user name and password 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
There must be no space between the
and the following password value.
If you omit the
password value following the
-p option on the command line, the
client prompts for one.
Specifying a password on the command line should be considered insecure. See Section 126.96.36.199, "End-User Guidelines for Password Security". You can use an option file to avoid giving the password on the command line.
For additional information about specifying user names, passwords, and other connection parameters, see Section 4.2.2, "Connecting to the MySQL Server".