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:

We do not believe in a complete code freeze because this prevents us from making bugfixes and other fixes that must be done. By “somewhat frozen” we mean that 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.

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, go with the General Availability release series. Currently, this is MySQL 5.1. 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. Note that development releases are not as stable as production releases.

If you want to use the very latest sources containing all current patches and bugfixes, you can use one of our Bazaar repositories. These are not “releases” as such, but are available as previews of the code on which future releases are to be based.

The MySQL naming scheme uses release names that consist of three numbers and a suffix; for example, mysql-5.0.14-rc. 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:

MySQL uses a naming scheme that is slightly different from most other products. In general, it is usually safe to use any version that has been out for a couple of weeks without being replaced by a new version within the same release series.

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 test the newest MySQL version in our internal production environment, on at least one machine. We have more than 100GB of data to work with.

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 C, MySQL Change History.

We use the following policy when updating MySQL:

Oracle Corporation provides a set of binary distributions of MySQL. In addition to binaries provided in platform-specific package formats, we offer binary distributions for a number of platforms in the form of compressed tar files (.tar.gz files). See Section 2.9, “Standard MySQL Installation Using a Binary Distribution”. For Windows distributions, see Section 2.10, “Installing MySQL on Windows”.

If you want to compile a debug version of MySQL from a source distribution, you should add --with-debug or --with-debug=full to the configure command used to configure the distribution and remove any -fomit-frame-pointer options.

MySQL installation packages can be downloaded from http://dev.mysql.com/downloads/. If the package you download is contained within a Zip archive, you need to extract the archive first.

The process for starting the wizard depends on the contents of the installation package you download. If there is a setup.exe file present, double-click it to start the installation process. If there is an .msi file present, double-click it to start the installation process.

There are three installation types available: Typical, Complete, and Custom.

The Typical installation type installs the MySQL server, the mysql command-line client, and the command-line utilities. The command-line clients and utilities include mysqldump, myisamchk, and several other tools to help you manage the MySQL server.

The Complete installation type installs all components included in the installation package. The full installation package includes components such as the embedded server library, the benchmark suite, support scripts, and documentation.

The Custom installation type gives you complete control over which packages you wish to install and the installation path that is used. See Section 2.10.3.3, “The Custom Installation Dialog”, for more information on performing a custom install.

If you choose the Typical or Complete installation types and click the Next button, you advance to the confirmation screen to verify your choices and begin the installation. If you choose the Custom installation type and click the Next button, you advance to the custom installation dialog, described in Section 2.10.3.3, “The Custom Installation Dialog”.

If you wish to change the installation path or the specific components that are installed by the MySQL Installation Wizard, choose the Custom installation type.

A tree view on the left side of the custom install dialog lists all available components. Components that are not installed have a red X icon; components that are installed have a gray icon. To change whether a component is installed, click that component's icon and choose a new option from the drop-down list that appears.

You can change the default installation path by clicking the Change... button to the right of the displayed installation path.

After choosing your installation components and installation path, click the Next button to advance to the confirmation dialog.

Once you choose an installation type and optionally choose your installation components, you advance to the confirmation dialog. Your installation type and installation path are displayed for you to review.

To install MySQL if you are satisfied with your settings, click the Install button. To change your settings, click the Back button. To exit the MySQL Installation Wizard without installing MySQL, click the Cancel button.

After installation is complete, you have the option of registering with the MySQL Web site. Registration gives you access to post in the MySQL forums at forums.mysql.com, along with the ability to report bugs at bugs.mysql.com and to subscribe to our newsletter. The final screen of the installer provides a summary of the installation and gives you the option to launch the MySQL Configuration Wizard, which you can use to create a configuration file, install the MySQL service, and configure security settings.

Once you click the Install button, the MySQL Installation Wizard begins the installation process and makes certain changes to your system which are described in the sections that follow.

Changes to the Registry

The MySQL Installation Wizard creates one Windows registry key in a typical install situation, located in HKEY_LOCAL_MACHINE\SOFTWARE\MySQL AB.

The MySQL Installation Wizard creates a key named after the major version of the server that is being installed, such as MySQL Server 5.0. It contains two string values, Location and Version. The Location string contains the path to the installation directory. In a default installation it contains C:\Program Files\MySQL\MySQL Server 5.0\. The Version string contains the release number. For example, for an installation of MySQL Server 5.0.92, the key contains a value of 5.0.92.

These registry keys are used to help external tools identify the installed location of the MySQL server, preventing a complete scan of the hard-disk to determine the installation path of the MySQL server. The registry keys are not required to run the server, and if you install MySQL using the noinstall Zip archive, the registry keys are not created.

Changes to the Start Menu

The MySQL Installation Wizard creates a new entry in the Windows Start menu under a common MySQL menu heading named after the major version of MySQL that you have installed. For example, if you install MySQL 5.0, the MySQL Installation Wizard creates a MySQL Server 5.0 section in the Start menu.

The following entries are created within the new Start menu section:

Changes to the File System

The MySQL Installation Wizard by default installs the MySQL 5.0 server to C:\Program Files\MySQL\MySQL Server 5.0, where Program Files is the default location for applications in your system, and 5.0 is the major version of your MySQL server. This is the recommended location for the MySQL server, replacing the former default location C:\mysql.

By default, all MySQL applications are stored in a common directory at C:\Program Files\MySQL, where Program Files is the default location for applications in your Windows installation. A typical MySQL installation on a developer machine might look like this:

C:\Program Files\MySQL\MySQL Server 5.0
C:\Program Files\MySQL\MySQL Workbench 5.1 OSS

This approach makes it easier to manage and maintain all MySQL applications installed on a particular system.

The MySQL Installation Wizard can perform server upgrades automatically using the upgrade capabilities of MSI. That means you do not need to remove a previous installation manually before installing a new release. The installer automatically shuts down and removes the previous MySQL service before installing the new version.

Automatic upgrades are available only when upgrading between installations that have the same major and minor version numbers. For example, you can upgrade automatically from MySQL 4.1.5 to MySQL 4.1.6, but not from MySQL 4.1 to MySQL 5.0.

See Section 2.10.14, “Upgrading MySQL on Windows”.

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, 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 2.10.3.1, “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 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 5.0\my.ini"

Here, C:\Program Files\MySQL\MySQL Server 5.0 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 and Windows XP, 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 2.10.4.10, “The Service Options Dialog”, and Section 2.10.4.11, “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 allows 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 allows 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.

It is strongly recommended that you set a root password for your MySQL server, and the MySQL Server Instance Configuration Wizard requires by default that you do so. If you do not wish to set a root password, uncheck the box next to the Modify Security Settings option.

To set the root password, enter the desired password into both the New root password and Confirm boxes. If you are reconfiguring an existing server, you need to enter the existing root password into the Current root password box.

To allow 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.

You can build MySQL on Windows by using a combination of cmake and Microsoft Visual Studio .NET 2003 (7.1), Microsoft Visual Studio 2005 (8.0) or Microsoft Visual C++ 2005 Express Edition. You must have the appropriate Microsoft Platform SDK installed.

Follow this procedure to build MySQL:

The Windows source distribution includes the necessary solution file and the vcproj files required to build each component. Using this method you are not able to select the storage engines that are included in your build.

Follow this procedure to build MySQL:

When you are satisfied that the program you have built is working correctly, stop the server. Now you can install the distribution. There are two ways to do this, either by using the supplied installation script or by copying the files individually by hand.

To use the script method you must have Cygwin installed as the script is a Shell script. To execute the installation process, run the make_win_bin_dist script in the scripts directory of the MySQL source distribution (see Section 4.4.2, “make_win_bin_dist — Package MySQL Distribution as ZIP Archive”). This is a shell script, so you must have Cygwin installed if you want to use it. It creates a Zip archive of the built executables and support files that you can unpack to your desired installation location.

It is also possible to install MySQL by copying directories and files manually:

After installation, set up and start the server in the same way as for binary Windows distributions. See Section 2.10, “Installing MySQL on Windows”.

You should test the server that you have built from source before using the distribution.

To test the server you need to run the built mysqld. By default, using the source build examples, the MySQL base directory and data directory are C:\mysql and C:\mysql\data. If you want to test your server using the source tree root directory and its data directory as the base directory and data directory, you need to tell the server their path names. You can either do this on the command line with the --basedir and --datadir options, or by placing appropriate options in an option file. (See Section 4.2.3.3, “Using Option Files”.) If you have an existing data directory elsewhere that you want to use, you can specify its path name instead.

When the server is running in standalone fashion or as a service based on your configuration, try to connect to it from the mysql interactive command-line utility.

You can also run the standard test script, mysql-test-run.pl. This script is written in Perl, so you'll need either Cygwin or ActiveState Perl to run it. You may also need to install the modules required by the script. To run the test script, change location into the mysql-test directory under the work directory, set the MTR_VS_CONFIG environment variable to the configuration you selected earlier (or use the --vs-config option), and invoke mysql-test-run.pl. For example (using Cygwin and the bash shell):

shell> cd mysql-test
shell> export MTR_VS_CONFIG=debug
shell> ./mysql-test-run.pl --force --timer
shell> ./mysql-test-run.pl --force --timer --ps-protocol

To create a Windows source package from the current Bazaar source tree, use the instructions here. This procedure must be performed on a system running a Unix or Unix-like operating system because some of the configuration and build steps require tools that work only on Unix. For example, the following procedure is known to work well on Linux.

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> bin/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 and the Mac OS X Startup Item 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), the mysql.server script is installed in the /etc/init.d directory with the name mysql. You need not install it manually. See Section 2.11, “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

Older Red Hat systems use the /etc/rc.d/init.d directory rather than /etc/init.d. Adjust the preceding commands accordingly. Alternatively, first create /etc/init.d as a symbolic link that points to /etc/rc.d/init.d:

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-4.1] and [mysqld-5.0] are read by servers having versions 4.1.x, 5.0.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 5.0.

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 2.10.13, “Troubleshooting a MySQL Installation Under Windows”.

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, BDB, NDB), be sure that you have them configured the way you want before starting the server:

MySQL Enterprise For expert advice on start-up options appropriate to your circumstances, subscribe to The MySQL Enterprise Monitor. For more information, see http://www.mysql.com/products/enterprise/advisors.html.

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 allow the 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 5.0\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 couldn't start. For example, you might see something like this in the log:

000729 14:50:10  bdb:  Recovery function for LSN 1 27595 failed
000729 14:50:10  bdb:  warning: ./test/t1.db: No such file or directory
000729 14:50:10  Can't init databases

This means that you did not start mysqld with the --bdb-no-recover option and Berkeley DB found something wrong with its own log files when it tried to recover your databases. To be able to continue, you should move the old Berkeley DB log files from the database directory to some other place, where you can later examine them. The BDB log files are named in sequence beginning with log.0000000001, where the number increases over time.

If you are running mysqld with BDB table support and mysqld dumps core at startup, this could be due to problems with the BDB recovery log. In this case, you can try starting mysqld with --bdb-no-recover. If that helps, you should remove all BDB log files from the data directory and try starting mysqld again without the --bdb-no-recover option.

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 5.6, “Running Multiple MySQL Servers on the Same 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'll 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'll also need to specify the port number for client programs when connecting to the server via 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 allow access to the port.

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

127.0.0.1       localhost

This problem occurs only on systems that do not have a working thread library and for which MySQL must be configured to use MIT-pthreads.

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.