( mysqld_multi

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 5.1.5 The `mysqld_multi' Program for Managing Multiple MySQL Servers
 `mysqld_multi' is meant for managing several `mysqld' processes that
 listen for connections on different Unix socket files and TCP/IP ports.
 It can start or stop servers, or report their current status.
 The program searches for groups named `[mysqld#]' in `my.cnf' (or in
 the file named by the `--config-file' option).  `#' can be any positive
 integer.  This number is referred to in the following discussion as the
 option group number, or GNR.  Group numbers distinguish option groups
 from one another and are used as arguments to `mysqld_multi' to specify
 which servers you want to start, stop, or obtain a status report for.
 Options listed in these groups are the same that you would use in the
 `[mysqld]' group used for starting `mysqld'.  (See, for example, 
 Automatic start.) However, when using multiple servers it is necessary
 that each one use its own value for options such as the Unix socket
 file and TCP/IP port number. For more information on which options must
 be unique per server in a multiple-server environment, see 
 Multiple servers.
 To invoke `mysqld_multi', use the following syntax:
      shell> mysqld_multi [OPTIONS] {start|stop|report} [GNR[,GNR]...]
 `start', `stop', and `report' indicate which operation you want to
 perform. You can perform the designated operation on a single server or
 multiple servers, depending on the GNR list that follows the option
 name.  If there is no list, `mysqld_multi' performs the operation for
 all servers in the option file.
 Each GNR value represents an option group number or range of group
 numbers.  The value should be the number at the end of the group name
 in the option file.  For example, the GNR for a group named `[mysqld17]'
 is `17'.  To specify a range of numbers, separate the first and last
 numbers by a dash.  The GNR value `10-13' represents groups
 `[mysqld10]' through `[mysqld13]'.  Multiple groups or group ranges can
 be specified on the command line, separated by commas.  There must be
 no whitespace characters (spaces or tabs) in the GNR list; anything
 after a whitespace character is ignored.
 This command starts a single server using option group `[mysqld17]':
      shell> mysqld_multi start 17
 This command stops several servers, using option groups `[mysql8]' and
 `[mysqld10]' through `[mysqld13]':
      shell> mysqld_multi stop 8,10-13
 For an example of how you might set up an option file, use this command:
      shell> mysqld_multi --example
 `mysqld_multi' supports the following options:
      Specify the name of an alternative option file. This affects where
      `mysqld_multi' looks for `[mysqld#]' option groups.  Without this
      option, all options are read from the usual `my.cnf' file.  The
      option does not affect where `mysqld_multi' reads its own options,
      which are always taken from the `[mysqld_multi]' group in the
      usual `my.cnf' file.
      Display a sample option file.
      Display a help message and exit.
      Specify the name of the log file. If the file exists, log output
      is appended to it.
      The `mysqladmin' binary to be used to stop servers.
      The `mysqld' binary to be used. Note that you can specify
      `mysqld_safe' as the value for this option also. The options are
      passed to `mysqld'. Just make sure that you have the directory
      where `mysqld' is located in your `PATH' environment variable
      setting or fix `mysqld_safe'.
      Print log information to stdout rather than to the log file. By
      default, output goes to the log file.
      The password of the MySQL account to use when invoking
      `mysqladmin'.  Note that the password value is not optional for
      this option, unlike for other MySQL programs.
      Disable warnings.  This option was added in MySQL 4.1.6.
      Connect to each MySQL server via the TCP/IP port instead of the
      Unix socket file.  (If a socket file is missing, the server might
      still be running, but accessible only via the TCP/IP port.)  By
      default, connections are made using the Unix socket file.  This
      option affects `stop' and `report' operations.
      The username of the MySQL account to use when invoking
      Be more verbose.  This option was added in MySQL 4.1.6.
      Display version information and exit.
 Some notes about `mysqld_multi':
    * Make sure that the MySQL account used for stopping the `mysqld'
      servers (with the `mysqladmin' program) has the same username and
      password for each server. Also, make sure that the account has the
      `SHUTDOWN' privilege. If the servers that you want to manage have
      many different usernames or passwords for the administrative
      accounts, you might want to create an account on each server that
      has the same username and password.  For example, you might set up
      a common `multi_admin' account by executing the following commands
      for each server:
           shell> mysql -u root -S /tmp/mysql.sock -pROOT_PASSWORD
           mysql> GRANT SHUTDOWN ON *.*
               -> TO 'multi_admin'@'localhost' IDENTIFIED BY 'multipass';
       Privileges.  You will have to do this for each `mysqld'
      server. Change the connection parameters appropriately when
      connecting to each one.  Note that the host part of the account
      name must allow you to connect as `multi_admin' from the host
      where you want to run `mysqld_multi'.
    * The `--pid-file' option is very important if you are using
      `mysqld_safe' to start `mysqld' (for example,
      `--mysqld=mysqld_safe') Every `mysqld' should have its own process
      ID file. The advantage of using `mysqld_safe' instead of `mysqld'
      is that `mysqld_safe' "guards" its `mysqld' process and will
      restart it if the process terminates due to a signal sent using
      `kill -9', or for other reasons, such as a segmentation fault.
      Please note that the `mysqld_safe' script might require that you
      start it from a certain place. This means that you might have to
      change location to a certain directory before running
      `mysqld_multi'. If you have problems starting, please see the
      `mysqld_safe' script. Check especially the lines:
           # Check if we are starting this relative (for the binary release)
           if test -d $MY_PWD/data/mysql -a -f ./share/mysql/english/errmsg.sys -a \
            -x ./bin/mysqld
       `mysqld_safe' mysqld_safe.  The test performed by these
      lines should be successful, or you might encounter problems.
    * The Unix socket file and the TCP/IP port number must be different
      for every `mysqld'.
    * You might want to use the `--user' option for `mysqld', but in
      order to do this you need to run the `mysqld_multi' script as the
      Unix `root' user. Having the option in the option file doesn't
      matter; you will just get a warning, if you are not the superuser
      and the `mysqld' processes are started under your own Unix account.
    * *Important*: Make sure that the data directory is fully accessible
      to the Unix account that the specific `mysqld' process is started
      as. _Do not_ use the Unix root account for this, unless you _know_
      what you are doing.
    * *Most important*: Before using `mysqld_multi' be sure that you
      understand the meanings of the options that are passed to the
      `mysqld' servers and _why_ you would want to have separate `mysqld'
      processes.  Beware of the dangers of using multiple `mysqld'
      servers with the same data directory.  Use separate data
      directories, unless you _know_ what you are doing.  Starting
      multiple servers with the same data directory _will not_ give you
      extra performance in a threaded system.   Multiple servers.
 The following example shows how you might set up an option file for use
 with `mysqld_multi'.  The first and fifth `[mysqld#]' group were
 intentionally left out from the example to illustrate that you can have
 "gaps" in the option file. This gives you more flexibility.  The order
 in which the `mysqld' programs are started or stopped depends on the
 order in which they appear in the option file.
      # This file should probably be in your home dir (~/.my.cnf)
      # or /etc/my.cnf
      # Version 2.1 by Jani Tolonen
      mysqld     = /usr/local/bin/mysqld_safe
      mysqladmin = /usr/local/bin/mysqladmin
      user       = multi_admin
      password   = multipass
      socket     = /tmp/mysql.sock2
      port       = 3307
      pid-file   = /usr/local/mysql/var2/hostname.pid2
      datadir    = /usr/local/mysql/var2
      language   = /usr/local/share/mysql/english
      user       = john
      socket     = /tmp/mysql.sock3
      port       = 3308
      pid-file   = /usr/local/mysql/var3/hostname.pid3
      datadir    = /usr/local/mysql/var3
      language   = /usr/local/share/mysql/swedish
      user       = monty
      socket     = /tmp/mysql.sock4
      port       = 3309
      pid-file   = /usr/local/mysql/var4/hostname.pid4
      datadir    = /usr/local/mysql/var4
      language   = /usr/local/share/mysql/estonia
      user       = tonu
      socket     = /tmp/mysql.sock6
      port       = 3311
      pid-file   = /usr/local/mysql/var6/hostname.pid6
      datadir    = /usr/local/mysql/var6
      language   = /usr/local/share/mysql/japanese
      user       = jani
  Option files.
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