The first decision to make is whether you want to use a production (stable) release or a development release. In the MySQL development process, multiple release series co-exist, each at a different stage of maturity.

Production Releases

Development Release

MySQL 4.1, 4.0, and 3.23 are old releases that are no longer supported.

See http://www.mysql.com/about/legal/lifecycle/ for information about support policies and schedules.

Normally, if you are beginning to use MySQL for the first time or trying to port it to some system for which there is no binary distribution, use the most recent General Availability series listed in the preceding descriptions. All MySQL releases, even those from development series, are checked with the MySQL benchmarks and an extensive test suite before being issued.

If you are running an older system and want to upgrade, but do not want to take the chance of having a nonseamless upgrade, you should upgrade to the latest version in the same release series you are using (where only the last part of the version number is newer than yours). We have tried to fix only fatal bugs and make only small, relatively “safe” changes to that version.

If you want to use new features not present in the production release series, you can use a version from a development series. Be aware that development releases are not as stable as production releases.

We do not use a complete code freeze because this prevents us from making bugfixes and other fixes that must be done. We may add small things that should not affect anything that currently works in a production release. Naturally, relevant bugfixes from an earlier series propagate to later series.

If you want to use the very latest sources containing all current patches and bugfixes, you can use one of our source code repositories (see Section 2.9.3, “Installing MySQL from a Development Source Tree”). These are not “releases” as such, but are available as previews of the code on which future releases are to be based.

The naming scheme in MySQL 5.5 uses release names that consist of three numbers and a suffix; for example, mysql-5.5.6-m3. The numbers within the release name are interpreted as follows:

For each minor update, the last number in the version string is incremented. When there are major new features or minor incompatibilities with previous versions, the second number in the version string is incremented. When the file format changes, the first number is increased.

Release names also include a suffix to indicates the stability level of the release. Releases within a series progress through a set of suffixes to indicate how the stability level improves. The possible suffixes are:

All releases of MySQL are run through our standard tests and benchmarks to ensure that they are relatively safe to use. Because the standard tests are extended over time to check for all previously found bugs, the test suite keeps getting better.

All releases have been tested at least with these tools:

We also perform additional integration and nonfunctional testing of the latest MySQL version in our internal production environment. Integration testing is done with different connectors, storage engines, replication modes, backup, partitioning, stored programs, and so forth in various combinations. Additional nonfunctional testing is done in areas of performance, concurrency, stress, high volume, upgrade and downgrade.

After choosing which version of MySQL to install, you should decide whether to use a binary distribution or a source distribution. In most cases, you should probably use a binary distribution, if one exists for your platform. Binary distributions are available in native format for many platforms, such as RPM files for Linux or PKG package installers for Mac OS X or Solaris. Distributions also are available as Zip archives or compressed tar files.

Reasons to choose a binary distribution include the following:

Under some circumstances, you may be better off installing MySQL from a source distribution:

MySQL is evolving quite rapidly and we want to share new developments with other MySQL users. We try to produce a new release whenever we have new and useful features that others also seem to have a need for.

We also try to help users who request features that are easy to implement. We take note of what our licensed users want, and we especially take note of what our support customers want and try to help them in this regard.

No one is required to download a new release. The News section helps you determine whether the new release has something you really want. See Appendix D, MySQL Change History.

We use the following policy when updating MySQL:

After you have downloaded a MySQL package, you should make sure that its MD5 checksum matches the one provided on the MySQL download pages. Each package has an individual checksum that you can verify with the following command, where package_name is the name of the package you downloaded:

shell> md5sum package_name

Example:

shell> md5sum mysql-standard-5.5.27-linux-i686.tar.gz
aaab65abbec64d5e907dcd41b8699945  mysql-standard-5.5.27-linux-i686.tar.gz

You should verify that the resulting checksum (the string of hexadecimal digits) matches the one displayed on the download page immediately below the respective package.

Note that not all operating systems support the md5sum command. On some, it is simply called md5, and others do not ship it at all. On Linux, it is part of the GNU Text Utilities package, which is available for a wide range of platforms. You can download the source code from http://www.gnu.org/software/textutils/ as well. If you have OpenSSL installed, you can use the command openssl md5 package_name instead. A Windows implementation of the md5 command line utility is available from http://www.fourmilab.ch/md5/. winMd5Sum is a graphical MD5 checking tool that can be obtained from http://www.nullriver.com/index/products/winmd5sum.

Another method of verifying the integrity and authenticity of a package is to use cryptographic signatures. This is more reliable than using MD5 checksums, but requires more work.

We sign MySQL downloadable packages with GnuPG (GNU Privacy Guard). GnuPG is an Open Source alternative to the well-known Pretty Good Privacy (PGP) by Phil Zimmermann. See http://www.gnupg.org/ for more information about GnuPG and how to obtain and install it on your system. Most Linux distributions ship with GnuPG installed by default. For more information about GnuPG, see http://www.openpgp.org/.

To verify the signature for a specific package, you first need to obtain a copy of our public GPG build key, which you can download from http://pgp.mit.com/. The key that you want to obtain is named mysql-build@oss.oracle.com. Alternatively, you can cut and paste the key directly from the following text:

-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: PGP Universal 2.9.1 (Build 347)
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=Eto8
-----END PGP PUBLIC KEY BLOCK-----

To import the build key into your personal public GPG keyring, use gpg --import. For example, if you have saved the key in a file named mysql_pubkey.asc, the import command looks like this:

shell> gpg --import mysql_pubkey.asc
gpg: key 5072E1F5: public key "MySQL Release Engineering
<mysql-build@oss.oracle.com>" imported
gpg: Total number processed: 1
gpg:               imported: 1
gpg: no ultimately trusted keys found

You can also download the key from the public keyserver using the public key id, 5072E1F5:

shell> gpg --recv-keys 5072E1F5
gpg: requesting key 5072E1F5 from hkp server keys.gnupg.net
gpg: key 5072E1F5: "MySQL Release Engineering <mysql-build@oss.oracle.com>"
1 new user ID
gpg: key 5072E1F5: "MySQL Release Engineering <mysql-build@oss.oracle.com>"
53 new signatures
gpg: no ultimately trusted keys found
gpg: Total number processed: 1
gpg:           new user IDs: 1
gpg:         new signatures: 53

If you want to import the key into your RPM configuration to validate RPM install packages, you should be able to import the key directly:

shell> rpm --import mysql_pubkey.asc

If you experience problems, try exporting the key from gpg and importing:

shell> gpg --export -a 5072e1f5 > 5072e1f5.asc
shell> rpm --import 5072e1f5.asc

Alternatively, rpm also supports loading the key directly from a URL, and you cas use this manual page:

shell> rpm --import http://dev.mysql.com/doc/refman/5.5/en/checking-gpg-signature.html

After you have downloaded and imported the public build key, download your desired MySQL package and the corresponding signature, which also is available from the download page. The signature file has the same name as the distribution file with an .asc extension, as shown by the examples in the following table.

Make sure that both files are stored in the same directory and then run the following command to verify the signature for the distribution file:

shell> gpg --verify package_name.asc

Example:

shell> gpg --verify mysql-standard-5.5.27-linux-i686.tar.gz.asc
gpg: Signature made Tue 01 Feb 2011 02:38:30 AM CST using DSA key ID 5072E1F5
gpg: Good signature from "MySQL Release Engineering <mysql-build@oss.oracle.com>"

The Good signature message indicates that everything is all right. You can ignore any insecure memory warning you might obtain.

See the GPG documentation for more information on how to work with public keys.

For RPM packages, there is no separate signature. RPM packages have a built-in GPG signature and MD5 checksum. You can verify a package by running the following command:

shell> rpm --checksig package_name.rpm

Example:

shell> rpm --checksig MySQL-server-5.5.27-0.glibc23.i386.rpm
MySQL-server-5.5.27-0.glibc23.i386.rpm: md5 gpg OK

shell> rpm --import mysql_pubkey.asc

If you need to obtain the MySQL public key, see Section 2.1.4.2, “Signature Checking Using GnuPG”.

After installation of the GUI version, the installer will have its own Start Menu item so that you can access it more easily.

To install MySQL Installer via the GUI, open the application, and click  Execute or Next when prompted.

After the installer itself has been installed and started, the following screen is displayed:

Figure 2.1. MySQL Installer - Welcome Screen

There are three main options:

When you click "Install MySQL Products," the Installer will find and install MySQL. But first, you'll need to accept the license agreement before proceeding. The license agreement is only displayed the initial time that MySQL Installer is executed:

Figure 2.2. MySQL Installer - License Agreement

If you are connected to the Internet, then the program will search for the latest MySQL components, and add them to the installation bundle, ensuring the best functionality. Click Connect to the Internet to complete this step, or if you'd rather not, check the Skip checkbox and continue.

Figure 2.3. MySQL Installer - Find latest products

If you chose "Connect to the Internet," the next page will show the progress of MySQL Installer's search for available updates. When the search is complete (or if you opted to skip the search), you will be taken to the Choose Setup Type page:

Figure 2.4. MySQL Installer - Choose Setup Type

Each type contains a description, so read the Setup Type Description to determine which option will be most compatible with your preferences.

The Installation and Data paths are also defined here, and a caution flag will notify you if the data path you are trying to establish already exists.

Once you select a setup type, the MySQL Installer will check your system for the necessary external requirements, and download and install any missing pieces onto your system.

Figure 2.5. MySQL Installer - Check Requirements

In the next window, you will be able to view a list of the MySQL components that are scheduled to be installed, and watch the progress of the installation.

Figure 2.6. MySQL Installer - Installation Progress

As components are installed, you'll see their status change from "to be installed" to "install success."

Figure 2.7. MySQL Installer - Installation Progress status

Once all components are installed, the next step is configuration. You can watch the progress of this step in the Configuration Overview window:

Figure 2.8. MySQL Installer - Configuration Overview

The ideal MySQL Server configuration depends on your intended use, as explained in the next window. Choose the description that most closely applies to your machine:

Figure 2.9. MySQL Installer - MySQL Server Configuration: Choose a platform

Next, choose your basic Network, Windows, and Security Settings:

Figure 2.10. MySQL Installer - MySQL Server Configuration: Basic settings

When the MySQL Installer configuration is complete, you can save the log and by default, the "Start MySQL Workbench after Setup" option is checked:

Figure 2.11. MySQL Installer - Installation Complete

You can now open MySQL Installer from the Microsoft Windows Start menu, which will pull up the MySQL Installer Maintenance Screen. This will be used to add, update, and remove features.

Figure 2.12. MySQL Installer - Maintenance Screen

See also the MySQL Workbench documentation (http://dev.mysql.com/doc/workbench/en/).

MySQL Installation Wizard is an installer for the MySQL server that uses the latest installer technologies for Microsoft Windows. The MySQL Installation Wizard, in combination with the MySQL Configuration Wizard, enables a user to install and configure a MySQL server that is ready for use immediately after installation.

The MySQL Installation Wizard is the standard installer for all MySQL server distributions, version 4.1.5 and higher. Users of previous versions of MySQL need to shut down and remove their existing MySQL installations manually before installing MySQL with the MySQL Installation Wizard. See Section 2.3.4.1.6, “Upgrading MySQL with the Installation Wizard”, for more information on upgrading from a previous version.

Microsoft has included an improved version of their Microsoft Windows Installer (MSI) in the recent versions of Windows. MSI has become the de-facto standard for application installations on Windows 2000, Windows XP, and Windows Server 2003. The MySQL Installation Wizard makes use of this technology to provide a smoother and more flexible installation process.

The Microsoft Windows Installer Engine was updated with the release of Windows XP; those using a previous version of Windows can reference this Microsoft Knowledge Base article for information on upgrading to the latest version of the Windows Installer Engine.

In addition, Microsoft has introduced the WiX (Windows Installer XML) toolkit recently. This is the first highly acknowledged Open Source project from Microsoft. We have switched to WiX because it is an Open Source project and it enables us to handle the complete Windows installation process in a flexible manner using scripts.

Improving the MySQL Installation Wizard depends on the support and feedback of users like you. If you find that the MySQL Installation Wizard is lacking some feature important to you, or if you discover a bug, please report it in our bugs database using the instructions given in Section 1.7, “How to Report Bugs or Problems”.

C:\Program Files\MySQL\MySQL Server 5.5
C:\Program Files\MySQL\MySQL Workbench 5.1 OSS

The Microsoft Installer (MSI) supports a both a quiet and a passive mode that can be used to install MySQL automatically without requiring intervention. You can use this either in scripts to automatically install MySQL or through a terminal connection such as Telnet where you do not have access to the standard Windows user interface. The MSI packages can also be used in combination with Microsoft's Group Policy system (part of Windows Server 2003 and Windows Server 2008) to install MySQL across multiple machines.

To install MySQL from one of the MSI packages automatically from the command line (or within a script), you need to use the msiexec.exe tool. For example, to perform a quiet installation (which shows no dialog boxes or progress):

shell> msiexec /i /quiet mysql-5.5.27.msi

The /i indicates that you want to perform an installation. The /quiet option indicates that you want no interactive elements.

To provide a dialog box showing the progress during installation, and the dialog boxes providing information on the installation and registration of MySQL, use /passive mode instead of /quiet:

shell> msiexec /i /passive mysql-5.5.27.msi

Regardless of the mode of the installation, installing the package in this manner performs a 'Typical' installation, and installs the default components into the standard location.

You can also use this method to uninstall MySQL by using the /uninstall or /x options:

shell> msiexec /x /quiet mysql-5.5.27.msi

To install MySQL and configure a MySQL instance from the command line, see Section 2.3.5.13, “MySQL Server Instance Config Wizard: Creating an Instance from the Command Line”.

For information on using MSI packages to install software automatically using Group Policy, see How to use Group Policy to remotely install software in Windows Server 2003.

To uninstall a MySQL where you have used the MSI packages, you must use the Add/Remove Programs tool within Control Panel. To do this:

When MySQL is removed using this method, only the installed components are removed. Any database information (including the tables and data), import or export files, log files, and binary logs produced during execution are kept in their configured location.

If you try to install MySQL again the information will be retained and you will be prompted to enter the password configured with the original installation.

If you want to delete MySQL completely:

The MySQL Server Instance Configuration Wizard is normally started as part of the installation process. You should only need to run the MySQL Server Instance Configuration Wizard again when you need to change the configuration parameters of your server.

If you chose not to open a port prior to installing MySQL on Windows Vista or newer, you can choose to use the MySQL Server Configuration Wizard after installation. However, you must open a port in the Windows Firewall. To do this see the instructions given in Section 2.3.4.1.1, “Downloading and Starting the MySQL Installation Wizard”. Rather than opening a port, you also have the option of adding MySQL as a program that bypasses the Windows Firewall. One or the other option is sufficient—you need not do both. Additionally, when running the MySQL Server Configuration Wizard on Windows Vista or newer, ensure that you are logged in as a user with administrative rights.

You can launch the MySQL Configuration Wizard by clicking the MySQL Server Instance Config Wizard entry in the MySQL section of the Windows Start menu.

Alternatively, you can navigate to the bin directory of your MySQL installation and launch the MySQLInstanceConfig.exe file directly.

The MySQL Server Instance Configuration Wizard places the my.ini file in the installation directory for the MySQL server. This helps associate configuration files with particular server instances.

To ensure that the MySQL server knows where to look for the my.ini file, an argument similar to this is passed to the MySQL server as part of the service installation:

--defaults-file="C:\Program Files\MySQL\MySQL Server 5.5\my.ini"

Here, C:\Program Files\MySQL\MySQL Server 5.5 is replaced with the installation path to the MySQL Server. The --defaults-file option instructs the MySQL server to read the specified file for configuration options when it starts.

Apart from making changes to the my.ini file by running the MySQL Server Instance Configuration Wizard again, you can modify it by opening it with a text editor and making any necessary changes. You can also modify the server configuration with the http://www.mysql.com/products/administrator/ utility. For more information about server configuration, see Section 5.1.2, “Server Command Options”.

MySQL clients and utilities such as the mysql and mysqldump command-line clients are not able to locate the my.ini file located in the server installation directory. To configure the client and utility applications, create a new my.ini file in the Windows installation directory (for example, C:\WINDOWS).

Under Windows Server 2003, Windows Server 2000, Windows XP, and Windows Vista, MySQL Server Instance Configuration Wizard will configure MySQL to work as a Windows service. To start and stop MySQL you use the Services application that is supplied as part of the Windows Administrator Tools.

If the MySQL Server Instance Configuration Wizard detects an existing configuration file, you have the option of either reconfiguring your existing server, or removing the server instance by deleting the configuration file and stopping and removing the MySQL service.

To reconfigure an existing server, choose the Re-configure Instance option and click the Next button. Any existing configuration file is not overwritten, but renamed (within the same directory) using a timestamp (Windows) or sequential number (Linux). To remove the existing server instance, choose the Remove Instance option and click the Next button.

If you choose the Remove Instance option, you advance to a confirmation window. Click the Execute button. The MySQL Server Configuration Wizard stops and removes the MySQL service, and then deletes the configuration file. The server installation and its data folder are not removed.

If you choose the Re-configure Instance option, you advance to the Configuration Type dialog where you can choose the type of installation that you wish to configure.

When you start the MySQL Server Instance Configuration Wizard for a new MySQL installation, or choose the Re-configure Instance option for an existing installation, you advance to the Configuration Type dialog.

There are two configuration types available: Detailed Configuration and Standard Configuration. The Standard Configuration option is intended for new users who want to get started with MySQL quickly without having to make many decisions about server configuration. The Detailed Configuration option is intended for advanced users who want more fine-grained control over server configuration.

If you are new to MySQL and need a server configured as a single-user developer machine, the Standard Configuration should suit your needs. Choosing the Standard Configuration option causes the MySQL Configuration Wizard to set all configuration options automatically with the exception of Service Options and Security Options.

The Standard Configuration sets options that may be incompatible with systems where there are existing MySQL installations. If you have an existing MySQL installation on your system in addition to the installation you wish to configure, the Detailed Configuration option is recommended.

To complete the Standard Configuration, please refer to the sections on Service Options and Security Options in Section 2.3.5.10, “The Service Options Dialog”, and Section 2.3.5.11, “The Security Options Dialog”, respectively.

There are three different server types available to choose from. The server type that you choose affects the decisions that the MySQL Server Instance Configuration Wizard makes with regard to memory, disk, and processor usage.

The Database Usage dialog enables you to indicate the storage engines that you expect to use when creating MySQL tables. The option you choose determines whether the InnoDB storage engine is available and what percentage of the server resources are available to InnoDB.

The Configuration Wizard uses a template to generate the server configuration file. The Database Usage dialog sets one of the following option strings:

Multifunctional Database:        MIXED
Transactional Database Only:     INNODB
Non-Transactional Database Only: MYISAM

When these options are processed through the default template (my-template.ini) the result is:

Multifunctional Database:
default-storage-engine=InnoDB
_myisam_pct=50

Transactional Database Only:
default-storage-engine=InnoDB
_myisam_pct=5

Non-Transactional Database Only:
default-storage-engine=MyISAM
_myisam_pct=100
skip-innodb

The _myisam_pct value is used to calculate the percentage of resources dedicated to MyISAM. The remaining resources are allocated to InnoDB.

Some users may want to locate the InnoDB tablespace files in a different location than the MySQL server data directory. Placing the tablespace files in a separate location can be desirable if your system has a higher capacity or higher performance storage device available, such as a RAID storage system.

To change the default location for the InnoDB tablespace files, choose a new drive from the drop-down list of drive letters and choose a new path from the drop-down list of paths. To create a custom path, click the ... button.

If you are modifying the configuration of an existing server, you must click the Modify button before you change the path. In this situation you must move the existing tablespace files to the new location manually before starting the server.

To prevent the server from running out of resources, it is important to limit the number of concurrent connections to the MySQL server that can be established. The Concurrent Connections dialog enables you to choose the expected usage of your server, and sets the limit for concurrent connections accordingly. It is also possible to set the concurrent connection limit manually.

Use the Networking Options dialog to enable or disable TCP/IP networking and to configure the port number that is used to connect to the MySQL server.

TCP/IP networking is enabled by default. To disable TCP/IP networking, uncheck the box next to the Enable TCP/IP Networking option.

Port 3306 is used by default. To change the port used to access MySQL, choose a new port number from the drop-down box or type a new port number directly into the drop-down box. If the port number you choose is in use, you are prompted to confirm your choice of port number.

Set the Server SQL Mode to either enable or disable strict mode. Enabling strict mode (default) makes MySQL behave more like other database management systems. If you run applications that rely on MySQL's old “forgiving” behavior, make sure to either adapt those applications or to disable strict mode. For more information about strict mode, see Section 5.1.6, “Server SQL Modes”.

The MySQL server supports multiple character sets and it is possible to set a default server character set that is applied to all tables, columns, and databases unless overridden. Use the Character Set dialog to change the default character set of the MySQL server.

On Windows platforms, the MySQL server can be installed as a Windows service. When installed this way, the MySQL server can be started automatically during system startup, and even restarted automatically by Windows in the event of a service failure.

The MySQL Server Instance Configuration Wizard installs the MySQL server as a service by default, using the service name MySQL. If you do not wish to install the service, uncheck the box next to the Install As Windows Service option. You can change the service name by picking a new service name from the drop-down box provided or by entering a new service name into the drop-down box.

To install the MySQL server as a service but not have it started automatically at startup, uncheck the box next to the Launch the MySQL Server Automatically option.

The content of the security options portion of the MySQL Server Instance Configuration Wizard will depend on whether this is a new installation, or modifying an existing installation.

To permit root logins from across the network, check the box next to the Enable root access from remote machines option. This decreases the security of your root account.

To create an anonymous user account, check the box next to the Create An Anonymous Account option. Creating an anonymous account can decrease server security and cause login and permission difficulties. For this reason, it is not recommended.

The final dialog in the MySQL Server Instance Configuration Wizard is the Confirmation Dialog. To start the configuration process, click the Execute button. To return to a previous dialog, click the Back button. To exit the MySQL Server Instance Configuration Wizard without configuring the server, click the Cancel button.

After you click the Execute button, the MySQL Server Instance Configuration Wizard performs a series of tasks and displays the progress onscreen as the tasks are performed.

The MySQL Server Instance Configuration Wizard first determines configuration file options based on your choices using a template prepared by MySQL developers and engineers. This template is named my-template.ini and is located in your server installation directory.

The MySQL Configuration Wizard then writes these options to the corresponding configuration file.

If you chose to create a service for the MySQL server, the MySQL Server Instance Configuration Wizard creates and starts the service. If you are reconfiguring an existing service, the MySQL Server Instance Configuration Wizard restarts the service to apply your configuration changes.

If you chose to set a root password, the MySQL Configuration Wizard connects to the server, sets your new root password, and applies any other security settings you may have selected.

After the MySQL Server Instance Configuration Wizard has completed its tasks, it displays a summary. Click the Finish button to exit the MySQL Server Configuration Wizard.

In addition to using the GUI interface to the MySQL Server Instance Config Wizard, you can also create instances automatically from the command line.

To use the MySQL Server Instance Config Wizard on the command line, you need to use the MySQLInstanceConfig.exe command that is installed with MySQL in the bin directory within the installation directory. MySQLInstanceConfig.exe takes a number of command-line arguments the set the properties that would normally be selected through the GUI interface, and then creates a new configuration file (my.ini) by combining these selections with a template configuration file to produce the working configuration file.

The main command line options are provided in the table below. Some of the options are required, while some options are optional.

The -t and -c options work together to set the configuration parameters for a new instance. The -t option specifies the template configuration file to use as the basic configuration, which are then merged with the configuration parameters generated by the MySQL Server Instance Config Wizard into the configuration file specified by the -c option.

A sample template file, my-template.ini is provided in the toplevel MySQL installation directory. The file contains elements are replaced automatically by the MySQL Server Instance Config Wizard during configuration.

If you specify a configuration file that already exists, the existing configuration file will be saved in the file with the original, with the date and time added. For example, the mysql.ini will be copied to mysql 2009-10-27 1646.ini.bak.

The parameters that you can specify on the command line are listed in the table below.

The following command installs a MySQL Server 5.5 instance from the directory C:\Program Files\MySQL\MySQL Server 5.5 using the service name MySQL55 and setting the root password to 1234.

shell> MySQLInstanceConfig.exe -i -q "-lC:\mysql_install_log.txt" »
   "-nMySQL Server 5.5" "-pC:\Program Files\MySQL\MySQL Server 5.5" -v5.5.27 »
   "-tmy-template.ini" "-cC:\mytest.ini" ServerType=DEVELOPMENT DatabaseType=MIXED »
   ConnectionUsage=DSS Port=3311 ServiceName=MySQL55 RootPassword=1234

In the above example, a log file will be generated in mysql_install_log.txt containing the information about the instance creation process. The log file generated by the above example is shown below:

Welcome to the MySQL Server Instance Configuration Wizard 1.0.16.0
Date: 2009-10-27 17:07:21

Installing service ...

Product Name:         MySQL Server 5.5
Version:              5.5.27
Installation Path:    C:\Program Files\MySQL\MySQL Server 5.5\

Creating configuration file C:\mytest.ini using template my-template.ini.
Options:
DEVELOPMENT
MIXED
DSS
STRICTMODE

Variables:
port: 3311
default-character-set: latin1
basedir: "C:/Program Files/MySQL/MySQL Server 5.5/"
datadir: "C:/Program Files/MySQL/MySQL Server 5.5/Data/"


Creating Windows service entry.
Service name: "MySQL55"
Parameters:   "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqld" --defaults-file="C:\mytest.ini" MySQL55.
Windows service MySQL55 installed.

When using the command line, the return values in the following table indicate an error performing the specified option.

You can perform an installation of MySQL automatically using the MSI package. For more information, see Section 2.3.4.2, “Automating MySQL Installation on Microsoft Windows using the MSI Package”.

To install MySQL manually, do the following:

If you need to specify startup options when you run the server, you can indicate them on the command line or place them in an option file. For options that are used every time the server starts, you may find it most convenient to use an option file to specify your MySQL configuration. This is particularly true under the following circumstances:

When the MySQL server starts on Windows, it looks for option files in several locations, such as the Windows directory, C:\, and the MySQL installation directory (for the full list of locations, see Section 4.2.3.3, “Using Option Files”). The Windows directory typically is named something like C:\WINDOWS. You can determine its exact location from the value of the WINDIR environment variable using the following command:

C:\> echo %WINDIR%

MySQL looks for options in each location first in the my.ini file, and then in the my.cnf file. However, to avoid confusion, it is best if you use only one file. If your PC uses a boot loader where C: is not the boot drive, your only option is to use the my.ini file. Whichever option file you use, it must be a plain text file.

You can also make use of the example option files included with your MySQL distribution; see Section 4.2.3.3.2, “Preconfigured Option Files”.

An option file can be created and modified with any text editor, such as Notepad. For example, if MySQL is installed in E:\mysql and the data directory is in E:\mydata\data, you can create an option file containing a [mysqld] section to specify values for the basedir and datadir options:

[mysqld]
# set basedir to your installation path
basedir=E:/mysql
# set datadir to the location of your data directory
datadir=E:/mydata/data

Note that Windows path names are specified in option files using (forward) slashes rather than backslashes. If you do use backslashes, double them:

[mysqld]
# set basedir to your installation path
basedir=E:\\mysql
# set datadir to the location of your data directory
datadir=E:\\mydata\\data

The rules for use of backslash in option file values are given in Section 4.2.3.3, “Using Option Files”.

The data directory is located within the AppData directory for the user running MySQL.

If you would like to use a data directory in a different location, you should copy the entire contents of the data directory to the new location. For example, if you want to use E:\mydata as the data directory instead, you must do two things:

The following table shows the available servers for Windows in MySQL 5.5.

All of the preceding binaries are optimized for modern Intel processors, but should work on any Intel i386-class or higher processor.

Each of the servers in a distribution support the same set of storage engines. The SHOW ENGINES statement displays which engines a given server supports.

All Windows MySQL 5.5 servers have support for symbolic linking of database directories.

MySQL supports TCP/IP on all Windows platforms. MySQL servers on Windows support named pipes as indicated in the following list. However, the default is to use TCP/IP regardless of platform. (Named pipes are slower than TCP/IP in many Windows configurations.)

Named pipes are enabled only if you start the server with the --enable-named-pipe option. It is necessary to use this option explicitly because some users have experienced problems with shutting down the MySQL server when named pipes were used.

This section gives a general overview of starting the MySQL server. The following sections provide more specific information for starting the MySQL server from the command line or as a Windows service.

The information here applies primarily if you installed MySQL using the Noinstall version, or if you wish to configure and test MySQL manually rather than with the GUI tools.

The examples in these sections assume that MySQL is installed under the default location of C:\Program Files\MySQL\MySQL Server 5.5. Adjust the path names shown in the examples if you have MySQL installed in a different location.

Clients have two options. They can use TCP/IP, or they can use a named pipe if the server supports named-pipe connections.

MySQL for Windows also supports shared-memory connections if the server is started with the --shared-memory option. Clients can connect through shared memory by using the --protocol=MEMORY option.

For information about which server binary to run, see Section 2.3.6.3, “Selecting a MySQL Server Type”.

Testing is best done from a command prompt in a console window (or “DOS window”). In this way you can have the server display status messages in the window where they are easy to see. If something is wrong with your configuration, these messages make it easier for you to identify and fix any problems.

To start the server, enter this command:

C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqld" --console

For a server that includes InnoDB support, you should see the messages similar to those following as it starts (the path names and sizes may differ):

InnoDB: The first specified datafile c:\ibdata\ibdata1 did not exist:
InnoDB: a new database to be created!
InnoDB: Setting file c:\ibdata\ibdata1 size to 209715200
InnoDB: Database physically writes the file full: wait...
InnoDB: Log file c:\iblogs\ib_logfile0 did not exist: new to be created
InnoDB: Setting log file c:\iblogs\ib_logfile0 size to 31457280
InnoDB: Log file c:\iblogs\ib_logfile1 did not exist: new to be created
InnoDB: Setting log file c:\iblogs\ib_logfile1 size to 31457280
InnoDB: Log file c:\iblogs\ib_logfile2 did not exist: new to be created
InnoDB: Setting log file c:\iblogs\ib_logfile2 size to 31457280
InnoDB: Doublewrite buffer not found: creating new
InnoDB: Doublewrite buffer created
InnoDB: creating foreign key constraint system tables
InnoDB: foreign key constraint system tables created
011024 10:58:25  InnoDB: Started

When the server finishes its startup sequence, you should see something like this, which indicates that the server is ready to service client connections:

mysqld: ready for connections
Version: '5.5.27'  socket: ''  port: 3306

The server continues to write to the console any further diagnostic output it produces. You can open a new console window in which to run client programs.

If you omit the --console option, the server writes diagnostic output to the error log in the data directory (C:\Program Files\MySQL\MySQL Server 5.5\data by default). The error log is the file with the .err extension.

The MySQL server can be started manually from the command line. This can be done on any version of Windows.

To start the mysqld server from the command line, you should start a console window (or “DOS window”) and enter this command:

C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqld"

The path to mysqld may vary depending on the install location of MySQL on your system.

You can stop the MySQL server by executing this command:

C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqladmin" -u root shutdown

This command invokes the MySQL administrative utility mysqladmin to connect to the server and tell it to shut down. The command connects as the MySQL root user, which is the default administrative account in the MySQL grant system. Note that users in the MySQL grant system are wholly independent from any login users under Windows.

If mysqld doesn't start, check the error log to see whether the server wrote any messages there to indicate the cause of the problem. The error log is located in the C:\Program Files\MySQL\MySQL Server 5.5\data directory. It is the file with a suffix of .err. You can also try to start the server as mysqld --console; in this case, you may get some useful information on the screen that may help solve the problem.

The last option is to start mysqld with the --standalone and --debug options. In this case, mysqld writes a log file C:\mysqld.trace that should contain the reason why mysqld doesn't start. See MySQL Internals: Porting.

Use mysqld --verbose --help to display all the options that mysqld supports.

To make it easier to invoke MySQL programs, you can add the path name of the MySQL bin directory to your Windows system PATH environment variable:

On Windows, the recommended way to run MySQL is to install it as a Windows service, whereby MySQL starts and stops automatically when Windows starts and stops. A MySQL server installed as a service can also be controlled from the command line using NET commands, or with the graphical Services utility. Generally, to install MySQL as a Windows service you should be logged in using an account that has administrator rights.

The Services utility (the Windows Service Control Manager) can be found in the Windows Control Panel (under Administrative Tools on Windows 2000, XP, Vista, and Server 2003). To avoid conflicts, it is advisable to close the Services utility while performing server installation or removal operations from the command line.

Before installing MySQL as a Windows service, you should first stop the current server if it is running by using the following command:

C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqladmin"
          -u root shutdown

This command invokes the MySQL administrative utility mysqladmin to connect to the server and tell it to shut down. The command connects as the MySQL root user, which is the default administrative account in the MySQL grant system. Note that users in the MySQL grant system are wholly independent from any login users under Windows.

Install the server as a service using this command:

C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqld" --install

The service-installation command does not start the server. Instructions for that are given later in this section.

To make it easier to invoke MySQL programs, you can add the path name of the MySQL bin directory to your Windows system PATH environment variable:

The following additional arguments can be used when installing the service:

For a MySQL server that is installed as a Windows service, the following rules determine the service name and option files that the server uses:

As a more complex example, consider the following command:

C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqld"
          --install MySQL --defaults-file=C:\my-opts.cnf

Here, the default service name (MySQL) is given after the --install option. If no --defaults-file option had been given, this command would have the effect of causing the server to read the [mysqld] group from the standard option files. However, because the --defaults-file option is present, the server reads options from the [mysqld] option group, and only from the named file.

You can also specify options as Start parameters in the Windows Services utility before you start the MySQL service.

Once a MySQL server has been installed as a service, Windows starts the service automatically whenever Windows starts. The service also can be started immediately from the Services utility, or by using a NET START MySQL command. The NET command is not case sensitive.

When run as a service, mysqld has no access to a console window, so no messages can be seen there. If mysqld does not start, check the error log to see whether the server wrote any messages there to indicate the cause of the problem. The error log is located in the MySQL data directory (for example, C:\Program Files\MySQL\MySQL Server 5.5\data). It is the file with a suffix of .err.

When a MySQL server has been installed as a service, and the service is running, Windows stops the service automatically when Windows shuts down. The server also can be stopped manually by using the Services utility, the NET STOP MySQL command, or the mysqladmin shutdown command.

You also have the choice of installing the server as a manual service if you do not wish for the service to be started automatically during the boot process. To do this, use the --install-manual option rather than the --install option:

C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqld" --install-manual

To remove a server that is installed as a service, first stop it if it is running by executing NET STOP MySQL. Then use the --remove option to remove it:

C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqld" --remove

If mysqld is not running as a service, you can start it from the command line. For instructions, see Section 2.3.6.5, “Starting MySQL from the Windows Command Line”.

Please see Section 2.3.7, “Troubleshooting a Microsoft Windows MySQL Server Installation”, if you encounter difficulties during installation.

You can test whether the MySQL server is working by executing any of the following commands:

C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqlshow"
C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqlshow" -u root mysql
C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysqladmin" version status proc
C:\> "C:\Program Files\MySQL\MySQL Server 5.5\bin\mysql" test

If mysqld is slow to respond to TCP/IP connections from client programs, there is probably a problem with your DNS. In this case, start mysqld with the --skip-name-resolve option and use only localhost and IP addresses in the Host column of the MySQL grant tables.

You can force a MySQL client to use a named-pipe connection rather than TCP/IP by specifying the --pipe or --protocol=PIPE option, or by specifying . (period) as the host name. Use the --socket option to specify the name of the pipe if you do not want to use the default pipe name.

Note that if you have set a password for the root account, deleted the anonymous account, or created a new user account, then you must use the appropriate -u and -p options with the commands shown above to connect with the MySQL Server. See Section 4.2.2, “Connecting to the MySQL Server”.

For more information about mysqlshow, see Section 4.5.6, “mysqlshow — Display Database, Table, and Column Information”.

The purpose of the mysql_install_db script is to generate new MySQL privilege tables. It does not overwrite existing MySQL privilege tables, and it does not affect any other data.

If you want to re-create your privilege tables, first stop the mysqld server if it is running. Then rename the mysql directory under the data directory to save it, and then run mysql_install_db. Suppose that your current directory is the MySQL installation directory and that mysql_install_db is located in the bin directory and the data directory is named data. To rename the mysql database and re-run mysql_install_db, use these commands.

shell> mv data/mysql data/mysql.old
shell> scripts/mysql_install_db --user=mysql

When you run mysql_install_db, you might encounter the following problems:

There are some alternatives to running the mysql_install_db script provided in the MySQL distribution:

Generally, you start the mysqld server in one of these ways:

The mysqld_safe and mysql.server scripts, Windows server, Solaris/OpenSolaris SMF, and the Mac OS X Startup Item (or MySQL Preference Pane) can be used to start the server manually, or automatically at system startup time. mysql.server and the Startup Item also can be used to stop the server.

To start or stop the server manually using the mysql.server script, invoke it with start or stop arguments:

shell> mysql.server start
shell> mysql.server stop

Before mysql.server starts the server, it changes location to the MySQL installation directory, and then invokes mysqld_safe. If you want the server to run as some specific user, add an appropriate user option to the [mysqld] group of the /etc/my.cnf option file, as shown later in this section. (It is possible that you will need to edit mysql.server if you've installed a binary distribution of MySQL in a nonstandard location. Modify it to change location into the proper directory before it runs mysqld_safe. If you do this, your modified version of mysql.server may be overwritten if you upgrade MySQL in the future, so you should make a copy of your edited version that you can reinstall.)

mysql.server stop stops the server by sending a signal to it. You can also stop the server manually by executing mysqladmin shutdown.

To start and stop MySQL automatically on your server, you need to add start and stop commands to the appropriate places in your /etc/rc* files.

If you use the Linux server RPM package (MySQL-server-VERSION.rpm), or a native Linux package installation, the mysql.server script may be installed in the /etc/init.d directory with the name mysql. See Section 2.5.1, “Installing MySQL from RPM Packages on Linux”, for more information on the Linux RPM packages.

Some vendors provide RPM packages that install a startup script under a different name such as mysqld.

If you install MySQL from a source distribution or using a binary distribution format that does not install mysql.server automatically, you can install it manually. The script can be found in the support-files directory under the MySQL installation directory or in a MySQL source tree.

To install mysql.server manually, copy it to the /etc/init.d directory with the name mysql, and then make it executable. Do this by changing location into the appropriate directory where mysql.server is located and executing these commands:

shell> cp mysql.server /etc/init.d/mysql
shell> chmod +x /etc/init.d/mysql

shell> cd /etc
shell> ln -s rc.d/init.d .

After installing the script, the commands needed to activate it to run at system startup depend on your operating system. On Linux, you can use chkconfig:

shell> chkconfig --add mysql

On some Linux systems, the following command also seems to be necessary to fully enable the mysql script:

shell> chkconfig --level 345 mysql on

On FreeBSD, startup scripts generally should go in /usr/local/etc/rc.d/. The rc(8) manual page states that scripts in this directory are executed only if their basename matches the *.sh shell file name pattern. Any other files or directories present within the directory are silently ignored. In other words, on FreeBSD, you should install the mysql.server script as /usr/local/etc/rc.d/mysql.server.sh to enable automatic startup.

As an alternative to the preceding setup, some operating systems also use /etc/rc.local or /etc/init.d/boot.local to start additional services on startup. To start up MySQL using this method, you could append a command like the one following to the appropriate startup file:

/bin/sh -c 'cd /usr/local/mysql; ./bin/mysqld_safe --user=mysql &'

For other systems, consult your operating system documentation to see how to install startup scripts.

You can add options for mysql.server in a global /etc/my.cnf file. A typical /etc/my.cnf file might look like this:

[mysqld]
datadir=/usr/local/mysql/var
socket=/var/tmp/mysql.sock
port=3306
user=mysql

[mysql.server]
basedir=/usr/local/mysql

The mysql.server script supports the following options: basedir, datadir, and pid-file. If specified, they must be placed in an option file, not on the command line. mysql.server supports only start and stop as command-line arguments.

The following table shows which option groups the server and each startup script read from option files.

[mysqld-major_version] means that groups with names like [mysqld-5.1] and [mysqld-5.5] are read by servers having versions 5.1.x, 5.5.x, and so forth. This feature can be used to specify options that can be read only by servers within a given release series.

For backward compatibility, mysql.server also reads the [mysql_server] group and mysqld_safe also reads the [safe_mysqld] group. However, you should update your option files to use the [mysql.server] and [mysqld_safe] groups instead when using MySQL 5.5.

For more information on MySQL configuration files and their structure and contents, see Section 4.2.3.3, “Using Option Files”.

This section provides troubleshooting suggestions for problems starting the server on Unix. If you are using Windows, see Section 2.3.7, “Troubleshooting a Microsoft Windows MySQL Server Installation”.

If you have problems starting the server, here are some things to try:

Some storage engines have options that control their behavior. You can create a my.cnf file and specify startup options for the engines that you plan to use. If you are going to use storage engines that support transactional tables (InnoDB, NDB), be sure that you have them configured the way you want before starting the server:

If you are using InnoDB tables, see Section 14.3.2, “Configuring InnoDB”.

Storage engines will use default option values if you specify none, but it is recommended that you review the available options and specify explicit values for those for which the defaults are not appropriate for your installation.

When the mysqld server starts, it changes location to the data directory. This is where it expects to find databases and where it expects to write log files. The server also writes the pid (process ID) file in the data directory.

The data directory location is hardwired in when the server is compiled. This is where the server looks for the data directory by default. If the data directory is located somewhere else on your system, the server will not work properly. You can determine what the default path settings are by invoking mysqld with the --verbose and --help options.

If the default locations do not match the MySQL installation layout on your system, you can override them by specifying options to mysqld or mysqld_safe on the command line or in an option file.

To specify the location of the data directory explicitly, use the --datadir option. However, normally you can tell mysqld the location of the base directory under which MySQL is installed and it looks for the data directory there. You can do this with the --basedir option.

To check the effect of specifying path options, invoke mysqld with those options followed by the --verbose and --help options. For example, if you change location into the directory where mysqld is installed and then run the following command, it shows the effect of starting the server with a base directory of /usr/local:

shell> ./mysqld --basedir=/usr/local --verbose --help

You can specify other options such as --datadir as well, but --verbose and --help must be the last options.

Once you determine the path settings you want, start the server without --verbose and --help.

If mysqld is currently running, you can find out what path settings it is using by executing this command:

shell> mysqladmin variables

Or:

shell> mysqladmin -h host_name variables

host_name is the name of the MySQL server host.

If you get Errcode 13 (which means Permission denied) when starting mysqld, this means that the privileges of the data directory or its contents do not permit server access. In this case, you change the permissions for the involved files and directories so that the server has the right to use them. You can also start the server as root, but this raises security issues and should be avoided.

On Unix, change location into the data directory and check the ownership of the data directory and its contents to make sure the server has access. For example, if the data directory is /usr/local/mysql/var, use this command:

shell> ls -la /usr/local/mysql/var

If the data directory or its files or subdirectories are not owned by the login account that you use for running the server, change their ownership to that account. If the account is named mysql, use these commands:

shell> chown -R mysql /usr/local/mysql/var
shell> chgrp -R mysql /usr/local/mysql/var

If it possible that even with correct ownership, MySQL may fail to start up if there is other security software running on your system that manages application access to various parts of the file system. In this case, you may need to reconfigure that software to enable mysqld to access the directories it uses during normal operation.

If the server fails to start up correctly, check the error log. Log files are located in the data directory (typically C:\Program Files\MySQL\MySQL Server 5.5\data on Windows, /usr/local/mysql/data for a Unix binary distribution, and /usr/local/var for a Unix source distribution). Look in the data directory for files with names of the form host_name.err and host_name.log, where host_name is the name of your server host. Then examine the last few lines of these files. On Unix, you can use tail to display them:

shell> tail host_name.err
shell> tail host_name.log

The error log should contain information that indicates why the server could not start.

If either of the following errors occur, it means that some other program (perhaps another mysqld server) is using the TCP/IP port or Unix socket file that mysqld is trying to use:

Can't start server: Bind on TCP/IP port: Address already in use
Can't start server: Bind on unix socket...

Use ps to determine whether you have another mysqld server running. If so, shut down the server before starting mysqld again. (If another server is running, and you really want to run multiple servers, you can find information about how to do so in Section 5.3, “Running Multiple MySQL Instances on One Machine”.)

If no other server is running, try to execute the command telnet your_host_name tcp_ip_port_number. (The default MySQL port number is 3306.) Then press Enter a couple of times. If you do not get an error message like telnet: Unable to connect to remote host: Connection refused, some other program is using the TCP/IP port that mysqld is trying to use. You will need to track down what program this is and disable it, or else tell mysqld to listen to a different port with the --port option. In this case, you will also need to specify the port number for client programs when connecting to the server using TCP/IP.

Another reason the port might be inaccessible is that you have a firewall running that blocks connections to it. If so, modify the firewall settings to permit access to the port.

If the server starts but you cannot connect to it, you should make sure that you have an entry in /etc/hosts that looks like this:

127.0.0.1       localhost

If you cannot get mysqld to start, you can try to make a trace file to find the problem by using the --debug option. See MySQL Internals: Porting.