Torbjorn Zetterlund

Wed 30 2011

Causes of MySQL Access Denied Errors

by bernt & torsten

If you encounter problems when you try to connect to the MySQL server, the following items describe some courses of action you can take to correct the problem. One of the most common issues that we found is with dedicated servers, many of the providers we used do not set up an account for root, so before you go down the list. Take a look at your website’s configuration and use the userid and password from your database setup, in most cases that work.

If that does not work, read on as we have added a page from the MySQL website that provides some information about possible causes of Access Denied errors. Make sure that the server is running. If it is not, clients cannot connect to it. For example, if an attempt to connect to the server fails with a message such as one of those following, one cause might be that the server is not running:

shell> mysql

ERROR 2003: Can’t connect to MySQL server on ‘host_name’ (111)

shell> mysql

ERROR 2002: Can’t connect to local MySQL server through socket

‘/tmp/mysql.sock’ (111)

It might be that the server is running, but you are trying to connect using a TCP/IP port, named pipe, or Unix socket file different from the one on which the server is listening. To correct this when you invoke a client program, specify a –port option to indicate the proper port number, or a –socket option to indicate the proper named pipe or Unix socket file. To find out where the socket file is, you can use this command:

shell> netstat -ln | grep mysql

Make sure that the server has not been configured to ignore network connections or (if you are attempting to connect remotely) that it has not been configured to listen only locally on its network interfaces. If the server was started with –skip-networking, it will not accept TCP/IP connections at all. If the server was started with –bind-address=, it will listen for TCP/IP connections only locally on the loopback interface and will not accept remote connections.

Check to make sure that there is no firewall blocking access to MySQL. Your firewall may be configured on the basis of the application being executed, or the port number used by MySQL for communication (3306 by default). Under Linux or Unix, check your IP tables (or similar) configuration to ensure that the port has not been blocked.  

The grant tables must be properly set up so that the server can use them for access control. For some distribution types (such as binary distributions on Windows, or RPM distributions on Linux), the installation process initializes the mysql database containing the grant tables.

To determine whether you need to initialize the grant tables, look for a mysql directory under the data directory. (The data directory normally is named data or var and is located under your MySQL installation directory.) Make sure that you have a file named user.MYD in the mysql database directory. If not, execute themysql_install_db script. After running this script and starting the server, test the initial privileges by executing this command:

shell> mysql -u root test

The server should let you connect without error.

After a fresh installation, you should connect to the server and set up your users and their access permissions:

shell> mysql -u root mysql

The server should let you connect because the MySQL root user has no password initially.  

If you have updated an existing MySQL installation to a newer version, did you run the mysql_upgrade script? If not, do so. The structure of the grant tables changes occasionally when new capabilities are added, so after an upgrade, you should always make sure that your tables have the current structure.

If a client program receives the following error message when it tries to connect, it means that the server expects passwords in a newer format than the client is capable of generating:

shell> mysql

The client does not support authentication protocol requested

by the server; consider upgrading MySQL client

For information on how to deal with this, see Section, “Password Hashing in MySQL, and Section B.5.2.4, Client does not support the authentication protocol.

Remember that client programs use connection parameters specified in option files or environment variables. If a client program seems to be sending incorrect default connection parameters when you have not specified them on the command line, check any applicable option files and your environment. For example, if you get Access denied when you run a client without any options, make sure that you have not specified an old password in any of your option files!

You can suppress the use of option files by a client program by invoking it with the –no-defaults option. For example:

shell> mysqladmin –no-defaults -u root version

The option files that clients use are listed in Section, “Using Option Files”. Environment variables are listed in Section 2.14, “Environment Variables”.

If you get the following error, it means that you are using an incorrect root password:

shell> mysqladmin -u root -pxxxx ver

Access denied for user ‘root’@’localhost’ (using password: YES)

If the preceding error occurs even when you have not specified a password, it means that you have an incorrect password listed in some option file. Try the –no-defaults option as described in the previous item.

For information on changing passwords, see Section 5.5.5, Assigning Account Passwords.

If you have lost or forgotten the root password, see Section B.5.4.1, “How to Reset the Root Password”.

If you change a password by using SET PASSWORD, INSERT, or UPDATE, you must encrypt the password using thePASSWORD() function. If you do not use PASSWORD() for these statements, the password will not work. For example, the following statement assigns a password but fails to encrypt it, so the user is not able to connect afterward:

SET PASSWORD FOR ‘abe’@’host_name’ = ‘eagle’;

Instead, set the password like this:

SET PASSWORD FOR ‘abe’@’host_name’ = PASSWORD(‘eagle’);

The PASSWORD() function is unnecessary when you specify a password using the CREATE USER or GRANTstatements or the mysqladmin password command. Each of those automatically uses PASSWORD() to encrypt the password. See Section 5.5.5, Assigning Account Passwords”, and Section, CREATE USER Syntax.

localhost is a synonym for your local hostname and is also the default host to which clients try to connect if you specify no host explicitly.

To avoid this problem on such systems, you can use a –host= option to name the server host explicitly. This will make a TCP/IP connection to the local mysqld server. You can also use TCP/IP by specifying a–host option that uses the actual hostname of the localhost. In this case, the hostname must be specified in a user table row on the server host, even though you are running the client program on the same host as the server.

The Access denied error message tells you who you are trying to log in as, the client host from which you are trying to connect, and whether you were using a password. Normally, you should have one row in the user table that exactly matches the hostname and user name that were given in the error message. For example, if you get an error message that contains using password: NO, it means that you tried to log in without a password.

If you get an Access denied error when trying to connect to the database with mysql -u user_name, you may have a problem with the user table. Check this by executing mysql -u root mysql and issuing this SQL statement:


The result should include a row with the Host and User columns matching your client’s hostname and your MySQL user name.

If the following error occurs when you try to connect from a host other than the one on which the MySQL server is running, it means that there is no row in the user table with a Host value that matches the client host:

Host … is not allowed to connect to this MySQL server

You can fix this by setting up an account for the combination of client hostname and user name that you are using when trying to connect.

If you do not know the IP number or hostname of the machine from which you are connecting, you should put a row with ‘%’ as the Host column value in the user table. After trying to connect from the client machine, use a SELECT USER() query to see how you really did connect. Then change the ‘%’ in the user table row to the actual hostname that shows up in the log. Otherwise, your system is left insecure because it allows connections from any host for the given user name.

On Linux, another reason that this error might occur is that you are using a binary MySQL version that is compiled with a different version of the glibc library than the one you are using. In this case, you should either upgrade your operating system or glibc, or download a source distribution of MySQL version and compile it yourself. A source RPM is normally trivial to compile and install, so this is not a big problem.

If you specify a hostname when trying to connect, but get an error message where the hostname is not shown or is an IP number, it means that the MySQL server got an error when trying to resolve the IP number of the client host to a name:

shell> mysqladmin -u root -pxxxx -h some_hostname ver

Access denied for user ‘root’@” (using password: YES)

If you try to connect as root and get the following error, it means that you do not have a row in the user table with a User column value of ‘root’ and that mysqld cannot resolve the hostname for your client:

Access denied for user ”@’unknown’

These errors indicate a DNS problem. To fix it, execute mysqladmin flush-hosts to reset the internal DNS hostname cache. See Section 7.5.11, How MySQL Uses DNS.

Some permanent solutions are:

  • Determine what is wrong with your DNS server and fix it.
  • Specify IP numbers rather than hostnames in the MySQL grant tables.
  • Put an entry for the client machine name in /etc/hosts on Unix or windowshosts on Windows.
  • Start mysqld with the –skip-name-resolve option.
  • Start mysqld with the –skip-host-cache option.

On Unix, if you are running the server and the client on the same machine, connect to localhost. Unix connections to localhost use a Unix socket file rather than TCP/IP.

On Windows, if you are running the server and the client on the same machine and the server supports named pipe connections, connect to the hostname . (period). Connections to . use a named pipe rather than TCP/IP.

If mysql -u root test works but mysql -h your_hostname -u root test results in Access denied(where your_hostname is the actual hostname of the local host), you may not have the correct name for your host in the user table. A common problem here is that the Host value in the user table row specifies an unqualified hostname, but your system’s name resolution routines return a fully qualified domain name (or vice versa). For example, if you have an entry with host ‘pluto’ in the user table, but your DNS tells MySQL that your hostname is ‘’, the entry does not work. Try adding an entry to the user table that contains the IP number of your host as the Host column value. (Alternatively, you could add an entry to the user table with a Host value that contains a wildcard; for example, ‘pluto.%’. However, use of Host values ending with “%” isinsecure and is not recommended!)

If mysql -u user_name test works but mysql -u user_name other_db does not, you have not granted access to the given user for the database named other_db.

If mysql -u user_name works when executed on the server host, but mysql -h host_name -u user_namedoes not work when executed on a remote client host, you have not enabled access to the server for the given user name from the remote host.

If you cannot figure out why you get Access denied, remove from the user table all entries that have Hostvalues containing wildcards (entries that contain ‘%’ or ‘_’ characters). A very common error is to insert a new entry with Host=’%’ and User=’some_user’, thinking that this allows you to specify localhost to connect from the same machine. The reason that this does not work is that the default privileges include an entry withHost=’localhost’ and User=”. Because that entry has a Host value ‘localhost’ that is more specific than’%’, it is used in preference to the new entry when connecting from localhost! The correct procedure is to insert a second entry with Host=’localhost’ and User=’some_user’, or to delete the entry with Host=’localhost’and User=”. After deleting the entry, remember to issue a FLUSH PRIVILEGES statement to reload the grant tables.

If you are able to connect to the MySQL server, but get an Access denied message whenever you issue a SELECT … INTO OUTFILE or LOAD DATA INFILE statement, your entry in the user table does not have theFILE privilege enabled.

If you change the grant tables directly (for example, by using INSERT, UPDATE, or DELETE statements) and your changes seem to be ignored, remember that you must execute a FLUSH PRIVILEGES statement or a mysqladmin flush-privileges command to cause the server to reload the privilege tables. Otherwise, your changes have no effect until the next time the server is restarted. Remember that after you change the root password with anUPDATE command, you will not need to specify the new password until after you flush the privileges, because the server will not know you’ve changed the password yet!

If your privileges seem to have changed in the middle of a session, it may be that a MySQL administrator has changed them. Reloading the grant tables affects new client connections, but it also affects existing connections as indicated in Section 5.4.6, “When Privilege Changes Take Effect”.

If you have access problems with a Perl, PHP, Python, or ODBC program, try to connect to the server with mysql -u user_name db_name or mysql -u user_name -pyour_pass db_name. If you are able to connect using the mysql client, the problem lies with your program, not with the access privileges. (There is no space between -p and the password; you can also use the –password=your_pass syntax to specify the password. If you use the-p or –password option with no password value, MySQL prompts you for the password.)

For testing purposes, start the mysqld server with the –skip-grant-tables option. Then you can change the MySQL grant tables and use the mysqlaccess script to check whether your modifications have the desired effect. When you are satisfied with your changes, execute mysqladmin flush-privileges to tell the mysqld server to reload the privileges. This enables you to begin using the new grant table contents without stopping and restarting the server.

If you get the following error, you may have a problem with the db or host table:

Access to database denied

If the entry selected from the db table has an empty value in the Host column, make sure that there are one or more corresponding entries in the host table specifying which hosts the db table entry applies to. This problem occurs infrequently because the host table is rarely used.

If everything else fails, start the mysqld server with a debugging option (for example, –debug=d,general,query). This prints host and user information about attempted connections, as well as information about each command issued.

If you have any other problems with the MySQL grant tables and feel you must post the problem to the mailing list, always provide a dump of the MySQL grant tables. You can dump the tables with the mysqldump mysql command. In some cases, you may need to restart mysqld with –skip-grant-tables to run mysqldump.