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mysqld_safe — MySQL Server Startup Script【manual】

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http://dev.mysql.com/doc/refman/5.5/en//mysqld-safe.html




4.3.2. mysqld_safe — MySQL Server Startup Script

mysqld_safe is the recommended way to
start a
mysqld
server on Unix.
mysqld_safe
adds some safety features such as restarting the server when an error occurs and logging runtime information to an error log file. A description of error logging is given later in this section.

mysqld_safe tries to start an executable
named
mysqld
. To override the default behavior and specify explicitly the name of the server you want to run, specify a

--mysqld
or
--mysqld-version
option to
mysqld_safe
. You can also use
--ledir
to indicate the directory where
mysqld_safe
should look for the server.

Many of the options to
mysqld_safe
are the same as the options to

mysqld
. See
Section 5.1.3, “Server Command Options”
.

Options unknown to
mysqld_safe
are passed to
mysqld
if they are specified on the command line, but ignored if they are specified in the
[mysqld_safe] group of an option file. See
Section 4.2.3.3, “Using Option Files”
.

mysqld_safe reads all options from the
[mysqld], [server], and
[mysqld_safe] sections in option files. For example, if you specify a
[mysqld] section like this,
mysqld_safe
will find and use the

--log-error
option:

[mysqld]
log-error=error.log

For backward compatibility,
mysqld_safe
also reads
[safe_mysqld]
sections, although you should rename such sections to
[mysqld_safe]
in MySQL 5.5 installations.

mysqld_safe supports the following options.
It also reads option files and supports the options for processing them described at

Section 4.2.3.4, “Command-Line Options that Affect Option-File Handling”
.

Table 4.1. mysqld_safe Options

Format Option File Description Introduced
--basedir=path basedir The path to the MySQL installation directory
--core-file-size=size core-file-size The size of the core file that mysqld should be able to create
--datadir=path datadir The path to the data directory
--defaults-extra-file=path defaults-extra-file The name of an option file to be read in addition to the usual option files
--defaults-file=file_name defaults-file The name of an option file to be read instead of the usual option files
--help
Display a help message and exit
--ledir=path ledir Use this option to indicate the path name to the directory where the server is located
--log-error=file_name log-error Write the error log to the given file
--malloc-lib=[lib-name] malloc-lib Alternative malloc library to use for mysqld
--mysqld=prog_name mysqld The name of the server program (in the ledir directory) that you want to start
--mysqld-version=suffix mysqld-version This option is similar to the --mysqld option, but you specify only the suffix for the server program name
--nice=priority nice Use the nice program to set the server's scheduling priority to the given value
--no-defaults no-defaults Do not read any option files
--open-files-limit=count open-files-limit The number of files that mysqld should be able to open
--pid-file=file_name pid-file=file_name The path name of the process ID file
--plugin-dir=path plugin-dir=path The directory where plugins are located 5.5.3
--port=number port The port number that the server should use when listening for TCP/IP connections
--skip-kill-mysqld skip-kill-mysqld Do not try to kill stray mysqld processes
--skip-syslog skip-syslog Do not write error messages to syslog; use error log file
--socket=path socket The Unix socket file that the server should use when listening for local connections
--syslog syslog Tag suffix for messages written to syslog
--timezone=timezone timezone Set the TZ time zone environment variable to the given option value
--user={user_name|user_id} user Run the mysqld server as the user having the name user_name or the numeric user ID user_id


  • --help

    Display a help message and exit.

  • --basedir=path

    The path to the MySQL installation directory.

  • --core-file-size=size

    The size of the core file that
    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. This must be the first option on the command line if it is used. If the file does not exist or is otherwise inaccessible, the server will exit with
    an error.

  • --defaults-file=file_name

    The name of an option file to be read instead of the usual option files. This must be the first option on the command line if it is used.

  • --ledir=path

    If
    mysqld_safe
    cannot find the server, use this option to indicate the path name to the directory where the server is located.

  • --log-error=file_name

    Write the error log to the given file. See
    Section 5.2.2, “The Error Log”
    .

  • --malloc-lib=[lib_name]

    The name of the library to use for memory allocation instead of the system
    malloc() library. Any library can be used by specifying its path name, but there is a shortcut form to enable use of the
    tcmalloc library that is shipped with binary MySQL distributions for Linux in MySQL 5.5.

    The
    --malloc-lib
    option works by modifying the
    LD_PRELOAD
    environment value to affect dynamic linking to enable the loader to find the memory-allocation library when

    mysqld
    runs:

    • If the option is not given, or is given without a value (--malloc-lib=),
      LD_PRELOAD is not modified and no attempt is made to use
      tcmalloc.

    • If the option is given as
      --malloc-lib=tcmalloc
      ,
      mysqld_safe
      looks for a
      tcmalloc
      library in /usr/lib and then in the MySQL
      pkglibdir location (for example,
      /usr/local/mysql/lib
      or whatever is appropriate). If
      tmalloc
      is found, its path name is added to the beginning of the
      LD_PRELOAD
      value for
      mysqld
      . If
      tcmalloc
      is not found,
      mysqld_safe
      aborts with an error.

    • If the option is given as
      --malloc-lib=/path/to/some/library
      , that full path is added to the beginning of the
      LD_PRELOAD value. If the full path points to a nonexistent or unreadable file,

      mysqld_safe
      aborts with an error.

    • For cases where
      mysqld_safe
      adds a path name to
      LD_PRELOAD, it adds the path to the beginning of any existing value the variable already has.

    Linux users can use the libtcmalloc_minimal.so included in binary packages by adding these lines to the
    my.cnf file:

    [mysqld_safe]
    malloc-lib=tcmalloc

    Those lines also suffice for users on any platform who have installed a
    tcmalloc package in /usr/lib. To use a specific
    tcmalloc library, specify its full path name. Example:

    [mysqld_safe]
    malloc-lib=/opt/lib/libtcmalloc_minimal.so
  • --mysqld=prog_name

    The name of the server program (in the
    ledir
    directory) that you want to start. This option is needed if you use the MySQL binary distribution but have the data directory outside of the binary distribution. If

    mysqld_safe
    cannot find the server, use the

    --ledir
    option to indicate the path name to the directory where the server is located.

  • --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=debug
    ,
    mysqld_safe
    starts the
    mysqld-debug
    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.

  • --no-defaults

    Do not read any option files. This must be the first option on the command line if it is used.

  • --open-files-limit=count

    The number of files that
    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=file_name

    The path name of the process ID file.

  • --plugin-dir=path

    The path name of the plugin directory. This option was added in MySQL 5.5.3.

  • --port=port_num

    The port number that the server should use when listening for TCP/IP connections. The port number must be 1024 or higher unless the server is started by the
    root system user.

  • --skip-kill-mysqld

    Do not try to kill stray
    mysqld
    processes at startup. This option works only on Linux.

  • --socket=path

    The Unix socket file that the server should use when listening for local connections.

  • --syslog,

    --skip-syslog

    --syslog causes error messages to be sent to
    syslog on systems that support the
    logger
    program. --skip-syslog suppresses the use of
    syslog; messages are written to an error log file.

    When syslog is used, the
    daemon.err syslog priority/facility is used for all log messages.

  • --syslog-tag=tag

    For logging to syslog, messages from

    mysqld_safe
    and
    mysqld
    are written with a tag of
    mysqld_safe and mysqld, respectively. To specify a suffix for the tag, use

    --syslog-tag=tag
    , which modifies the tags to be
    mysqld_safe-tag and
    mysqld-tag.

  • --timezone=timezone

    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.)

If you execute
mysqld_safe
with the
--defaults-file
or
--defaults-extra-file
option to name an option file, the option must be the first one given on the command line or the option file will not be used. For example, this command will not use the named option file:

mysql> mysqld_safe --port=port_num --defaults-file=file_name

Instead, use the following command:

mysql> mysqld_safe --defaults-file=file_name --port=port_num

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 working directory (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 path names. 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
tries 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.

Beginning with MySQL 5.5.21,
mysqld_safe
tries to use the
sleep
and date system utilities to determine how many times it has attempted to start this second, and—if these are present and this is greater than 5 times—is forced to wait 1 full second
before starting again. This is intended to prevent excessive CPU usage in the event of repeated failures. (Bug #11761530, Bug #54035)

When you use
mysqld_safe
to start
mysqld
,
mysqld_safe
arranges for error (and notice) messages from itself and from

mysqld
to go to the same destination.

There are several
mysqld_safe
options for controlling the destination of these messages:

  • --syslog: Write error messages to
    syslog on systems that support the
    logger
    program.

  • --skip-syslog: Do not write error messages to
    syslog. Messages are written to the default error log file (host_name.err in the data directory), or to a named file if the

    --log-error
    option is given.

  • --log-error=file_name:
    Write error messages to the named error file.

If none of these options is given, the default is

--skip-syslog
.

If
--syslog
and
--log-error
are both given, a warning is issued and

--log-error
takes precedence.

When
mysqld_safe
writes a message, notices go to the logging destination (syslog or the error log file) and
stdout. Errors go to the logging destination and
stderr
.

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. 

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