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mysqld_multi (1)


mysqld_multi - manage multiple MySQL servers


mysqld_multi [options] {start|stop|report} [GNR[,GNR] ...]


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     mysqld_multi - manage multiple MySQL servers

     mysqld_multi [options] {start|stop|report} [GNR[,GNR] ...]

     mysqld_multi is designed to manage 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.

     mysqld_multi searches for groups named [mysqldN] in my.cnf
     (or in the file named by the --config-file option).  N 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, Section, "Starting and Stopping
     MySQL Automatically".) 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 Section 5.3, "Running
     Multiple MySQL Instances on One Machine".

     To invoke mysqld_multi, use the following syntax:

         shell> mysqld_multi [options] {start|stop|report} [GNR[,GNR] ...]

     start, stop, and report indicate which operation to perform.
     You can perform the designated operation for 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

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         shell> mysqld_multi start 17

     This command stops several servers, using option groups
     [mysqld8] 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 searches for option files as follows:

     o   With --no-defaults, no option files are read.

     o   With --defaults-file=file_name, only the named file is

     o   Otherwise, option files in the standard list of
         locations are read, including any file named by the
         --defaults-extra-file=file_name option, if one is given.
         (If the option is given multiple times, the last value
         is used.)

     Option files read are searched for [mysqld_multi] and
     [mysqldN] option groups. The [mysqld_multi] group can be
     used for options to mysqld_multi itself.  [mysqldN] groups
     can be used for options passed to specific mysqld instances.

     The [mysqld] or [mysqld_safe] groups can be used for common
     options read by all instances of mysqld or mysqld_safe. You
     can specify a --defaults-file=file_name option to use a
     different configuration file for that instance, in which
     case the [mysqld] or [mysqld_safe] groups from that file
     will be used for that instance.

     mysqld_multi supports the following options.

     o   --help

         Display a help message and exit.

     o   --config-file=file_name

         This option is deprecated. If given, it is treated the
         same way as --defaults-extra-file, described earlier.
         --config-file was removed in MySQL 5.5.3.

     o   --example

         Display a sample option file.

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     o   --log=file_name

         Specify the name of the log file. If the file exists,
         log output is appended to it.

     o   --mysqladmin=prog_name

         The mysqladmin binary to be used to stop servers.

     o   --mysqld=prog_name

         The mysqld binary to be used. Note that you can specify
         mysqld_safe as the value for this option also. If you
         use mysqld_safe to start the server, you can include the
         mysqld or ledir options in the corresponding [mysqldN]
         option group. These options indicate the name of the
         server that mysqld_safe should start and the path name
         of the directory where the server is located. (See the
         descriptions for these options in mysqld_safe(1).)

             mysqld = mysqld-debug
             ledir  = /opt/local/mysql/libexec

     o   --no-log

         Print log information to stdout rather than to the log
         file. By default, output goes to the log file.

     o   --password=password

         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.

     o   --silent

         Silent mode; disable warnings.

     o   --tcp-ip

         Connect to each MySQL server through 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 through the TCP/IP port.) By default,
         connections are made using the Unix socket file. This
         option affects stop and report operations.

     o   --user=user_name

         The user name of the MySQL account to use when invoking

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     o   --verbose

         Be more verbose.

     o   --version

         Display version information and exit.

     Some notes about mysqld_multi:

     o   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 does not give you extra
         performance in a threaded system. See Section 5.3,
         "Running Multiple MySQL Instances on One Machine".


             Make sure that the data directory for each server 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. See Section 6.1.5, "How to Run MySQL
             as a Normal User".

     o   Make sure that the MySQL account used for stopping the
         mysqld servers (with the mysqladmin program) has the
         same user name and password for each server. Also, make
         sure that the account has the SHUTDOWN privilege. If the
         servers that you want to manage have different user
         names or passwords for the administrative accounts, you
         might want to create an account on each server that has
         the same user name 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 -p
             Enter password:
             mysql> GRANT SHUTDOWN ON *.*
                 -> TO 'multi_admin'@'localhost' IDENTIFIED BY 'multipass';

         See Section 6.2, "The MySQL Access Privilege System".
         You have to do this for each mysqld server. Change the
         connection parameters appropriately when connecting to

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         each one. Note that the host name part of the account
         name must permit you to connect as multi_admin from the
         host where you want to run mysqld_multi.

     o   The Unix socket file and the TCP/IP port number must be
         different for every mysqld. (Alternatively, if the host
         has multiple network addresses, you can use
         --bind-address to cause different servers to listen to
         different interfaces.)

     o   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 monitors its
         mysqld process and restarts 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

         The test performed by these lines should be successful,
         or you might encounter problems. See mysqld_safe(1).

     o   You might want to use the --user option for mysqld, but
         to do this you need to run the mysqld_multi script as
         the Unix superuser (root). Having the option in the
         option file doesn't matter; you just get a warning if
         you are not the superuser and the mysqld processes are
         started under your own Unix account.

     The following example shows how you might set up an option
     file for use with mysqld_multi. The order in which the
     mysqld programs are started or stopped depends on the order
     in which they appear in the option file. Group numbers need
     not form an unbroken sequence. The first and fifth [mysqldN]
     groups were intentionally omitted from the example to
     illustrate that you can have "gaps" in the option file. This
     gives you more flexibility.

         # This file should probably be in your home dir (~/.my.cnf)

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         # 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

     See Section, "Using Option Files".

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