MySQL Database Administration - 4.1.3 The mysqld_safe Server Startup Script
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mysqld_safe is the recommended way to start a mysqld server on Unix and NetWare. mysqld_safe adds some safety features such as restarting the server when an error occurs and logging runtime information to an error log file. NetWare-specific behaviors are listed later in this section.
Note: Before MySQL 4.0, mysqld_safe is named safe_mysqld. To preserve backward compatibility, MySQL binary distributions for some time will include safe_mysqld as a symbolic link to mysqld_safe.
By default, mysqld_safe tries to start an executable named mysqld-max if it exists, or mysqld otherwise. Be aware of the implications of this behavior:
On Linux, the MySQL-Max RPM relies on this mysqld_safe behavior. The RPM installs an executable named mysqld-max, which causes mysqld_safe to automatically use that executable from that point on.
If you install a MySQL-Max distribution that includes a server named mysqld-max, then upgrade later to a non-Max version of MySQL, mysqld_safe will still attempt to run the old mysqld-max server. If you perform such an upgrade, you should manually remove the old mysqld-max server to ensure that mysqld_safe runs the new mysqld server.
To override the default behavior and specify explicitly which server you want to run, specify a --mysqld or --mysqld-version option to mysqld_safe.
Many of the options to mysqld_safe are the same as the options to mysqld. See Section 4.2.1, "mysqld Command-Line Options."
All options specified to mysqld_safe on the command line are passed to mysqld. If you want to use any options that are specific to mysqld_safe and that mysqld doesn't support, do not specify them on the command line. Instead, list them in the [mysqld_safe] group of an option file. See Section 3.3.2, "Using Option Files."
mysqld_safe reads all options from the [mysqld], [server], and [mysqld_safe] sections in option files. For backward compatibility, it also reads [safe_mysqld] sections, although you should rename such sections to [mysqld_safe] when you begin using MySQL 4.0 or later.
mysqld_safe supports the following options:
--basedir=path
The path to the MySQL installation directory.
--core-file-size=size
The size of the core file mysqld should be able to create. The option value is passed to ulimit -c.
--datadir=path
The path to the data directory.
--defaults-extra-file=path
The name of an option file to be read in addition to the usual option files.
--defaults-file=path
The name of an option file to be read instead of the usual option files.
--err-log=path
The old form of the --log-error option, to be used before MySQL 4.0.
--ledir=path
The path to the directory containing the mysqld program. Use this option to explicitly indicate the location of the server.
--log-error=path
Write the error log to the given file. See Section 4.8.1, "The Error Log."
--mysqld=prog_name
The name of the server program (in the ledir directory) that you want to start.
--mysqld-version=suffix
This option is similar to the --mysqld option, but you specify only the suffix for the server program name. The basename is assumed to be mysqld. For example, if you use --mysqld-version=max, mysqld_safe will start the mysqld-max program in the ledir directory. If the argument to --mysqld-version is empty, mysqld_safe uses mysqld in the ledir directory.
--nice=priority
Use the nice program to set the server's scheduling priority to the given value. This option was added in MySQL 4.0.14.
--no-defaults
Do not read any option files.
--open-files-limit=count
The number of files mysqld should be able to open. The option value is passed to ulimit -n. Note that you need to start mysqld_safe as root for this to work properly!
--pid-file=path
The path to the process ID file.
--port=port_num
The port number to use when listening for TCP/IP connections.
--socket=path
The Unix socket file to use for local connections.
--timezone=zone
Set the TZ time zone environment variable to the given option value. Consult your operating system documentation for legal time zone specification formats.
--user={user_name | user_id}
Run the mysqld server as the user having the name user_name or the numeric user ID user_id. ("User" in this context refers to a system login account, not a MySQL user listed in the grant tables.)
The mysqld_safe script is written so that it normally can start a server that was installed from either a source or a binary distribution of MySQL, even though these types of distributions typically install the server in slightly different locations. (See Section 2.1.5, "Installation Layouts.") mysqld_safe expects one of the following conditions to be true:
The server and databases can be found relative to the directory from which mysqld_safe is invoked. For binary distributions, mysqld_safe looks under its working directory for bin and data directories. For source distributions, it looks for libexec and var directories. This condition should be met if you execute mysqld_safe from your MySQL installation directory (for example, /usr/local/mysql for a binary distribution).
If the server and databases cannot be found relative to the working directory, mysqld_safe attempts to locate them by absolute pathnames. Typical locations are /usr/local/libexec and
/usr/local/var. The actual locations are determined from the values configured into the distribution at the time it was built. They should be correct if MySQL is installed in the location specified at configuration time.
Because mysqld_safe will try to find the server and databases relative to its own working directory, you can install a binary distribution of MySQL anywhere, as long as you run mysqld_safe from the MySQL installation directory:
shell> cd mysql_installation_directory
shell> bin/mysqld_safe &
If mysqld_safe fails, even when invoked from the MySQL installation directory, you can specify the --ledir and --datadir options to indicate the directories in which the server and databases are located on your system.
Normally, you should not edit the mysqld_safe script. Instead, configure mysqld_safe by using command-line options or options in the [mysqld_safe] section of a my.cnf option file. In rare cases, it might be necessary to edit mysqld_safe to get it to start the server properly. However, if you do this, your modified version of mysqld_safe might be overwritten if you upgrade MySQL in the future, so you should make a copy of your edited version that you can reinstall.
On NetWare, mysqld_safe is a NetWare Loadable Module (NLM) that is ported from the original Unix shell script. It does the following:
Runs a number of system and option checks.
Runs a check on MyISAM and ISAM tables.
Provides a screen presence for the MySQL server.
Starts mysqld, monitors it, and restarts it if it terminates in error.
Sends error messages from mysqld to the host_name.err file in the data directory.
Sends mysqld_safe screen output to the host_name.safe file in the data directory.
Next: 4.1.4 The mysql.server Server Startup Script >>
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 This article is excerpted from chapter four of the book MySQL Administrator's Guide, written by Paul Dubois (Sams; ISBN: 0672326345). Check it out today at your favorite bookstore. Buy this book now.
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