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Updated: Wednesday, July 27, 2022

mysqld_multi (1)


mysqld_multi - manage multiple MySQL servers


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


MYSQLD_MULTI(1)              MySQL Database System             MYSQLD_MULTI(1)

       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.

           For some Linux platforms, MySQL installation from RPM or Debian
           packages includes systemd support for managing MySQL server startup
           and shutdown. On these platforms, mysqld_multi is not installed
           because it is unnecessary. For information about using systemd to
           handle multiple MySQL instances, see Section 2.5.10, "Managing
           MySQL Server with systemd".

       mysqld_multi searches for groups named [mysqldN] in my.cnf (or in the
       file named by the --defaults-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 2.10.5, "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 5.7, "Running Multiple MySQL
       Instances on One Machine".

       To invoke mysqld_multi, use the following syntax:

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

       start, stop, reload (stop and restart), 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 [mysqld17]:

           mysqld_multi start 17

       This command stops several servers, using option groups [mysqld8] and
       [mysqld10] through [mysqld13]:

           mysqld_multi stop 8,10-13

       For an example of how you might set up an option file, use this

           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 read.

       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.)

       For additional information about these and other option-file options,
       see Section, "Command-Line Options that Affect Option-File

       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 are used for that instance.

       mysqld_multi supports the following options.

       o   --help Display a help message and exit.

       o   --example Display a sample option file.

       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

       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).) Example:

               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 mysqladmin.

       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 5.7, "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

               $> mysql -u root -S /tmp/mysql.sock -p
               Enter password:
               mysql> CREATE USER 'multi_admin'@'localhost' IDENTIFIED BY 'multipass';
               mysql> GRANT SHUTDOWN ON *.* TO 'multi_admin'@'localhost';

           See Section 6.2, "Access Control and Account Management". You have
           to do this for each mysqld server. Change the connection parameters
           appropriately when connecting to 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 set the bind_address system variable 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.

       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 is an example of a my.cnf file for mysqld_multi.
           # Usually this file is located in home dir ~/.my.cnf or /etc/my.cnf
           mysqld     = /usr/local/mysql/bin/mysqld_safe
           mysqladmin = /usr/local/mysql/bin/mysqladmin
           user       = multi_admin
           password   = my_password
           socket     = /tmp/mysql.sock2
           port       = 3307
           pid-file   = /usr/local/mysql/data2/hostname.pid2
           datadir    = /usr/local/mysql/data2
           language   = /usr/local/mysql/share/mysql/english
           user       = unix_user1
           mysqld     = /path/to/mysqld_safe
           ledir      = /path/to/mysqld-binary/
           mysqladmin = /path/to/mysqladmin
           socket     = /tmp/mysql.sock3
           port       = 3308
           pid-file   = /usr/local/mysql/data3/hostname.pid3
           datadir    = /usr/local/mysql/data3
           language   = /usr/local/mysql/share/mysql/swedish
           user       = unix_user2
           socket     = /tmp/mysql.sock4
           port       = 3309
           pid-file   = /usr/local/mysql/data4/hostname.pid4
           datadir    = /usr/local/mysql/data4
           language   = /usr/local/mysql/share/mysql/estonia
           user       = unix_user3
           socket     = /tmp/mysql.sock6
           port       = 3311
           pid-file   = /usr/local/mysql/data6/hostname.pid6
           datadir    = /usr/local/mysql/data6
           language   = /usr/local/mysql/share/mysql/japanese
           user       = unix_user4

       See Section, "Using Option Files".

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       |Availability   | database/mysql-57 |
       |Stability      | Uncommitted       |

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MySQL 5.7                         03/21/2022                   MYSQLD_MULTI(1)