mysqld_multi - manage multiple MySQL servers at Linux.org

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MYSQLD_MULTI(1) MySQL Database System MYSQLD_MULTI(1)

NAME
mysqld_multi - manage multiple MySQL servers

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

DESCRIPTION
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. The MySQL
Instance Manager is an alternative means of managing multiple servers (see mysqlmanager(8)).

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 2.13.1.2, “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 5.6, “Running Multiple MySQL Servers on the Same 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 [mysqld17]:

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

As of MySQL 5.1.18, mysqld_multi searches for option files as follows:

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

· With --defaults-file=file_name, only the named file is read.

· 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

file for that instance, in which case the [mysqld] or [mysqld_safe] groups from that file will be used for
that instance. Before MySQL 5.1.35, some versions of mysqld_multi pass the --no-defaults options to instances,
so these techniques are inapplicable.

mysqld_multi supports the following options.

· --help

Display a help message and exit.

· --config-file=file_name

As of MySQL 5.1.18, this option is deprecated. If given, it is treated the same way as
--defaults-extra-file, described earlier. --config-file is removed in MySQL 5.5.

Before MySQL 5.1.18, this option specifies the name of an extra option file. It affects where mysqld_multi
looks for [mysqldN] 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.

· --example

Display a sample option file.

· --log=file_name

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

· --mysqladmin=prog_name

The mysqladmin binary to be used to stop servers.

· --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:

[mysqld38]
mysqld = mysqld-debug
ledir = /opt/local/mysql/libexec

· --no-log

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

· --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.

· --silent

· --verbose

Be more verbose.

· --version

Display version information and exit.

Some notes about mysqld_multi:

· 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 5.6, “Running Multiple MySQL Servers on the Same
Machine”.

Important
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 5.3.6, “How to Run MySQL as a Normal User”.

· 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 5.4, “The MySQL Access Privilege System”. 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 allow you to connect as multi_admin from the host where you want to run mysqld_multi.

· 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.)

· 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:

----------------------------------------------------------------

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)
# or /etc/my.cnf
# Version 2.1 by Jani Tolonen
[mysqld_multi]
mysqld = /usr/local/bin/mysqld_safe
mysqladmin = /usr/local/bin/mysqladmin
user = multi_admin
password = multipass
[mysqld2]
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
[mysqld3]
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
[mysqld4]
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
[mysqld6]
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 4.2.3.3, “Using Option Files”.

This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU
General Public License as published by the Free Software Foundation; version 2 of the License.

This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public
Sun Microsystems, Inc. (http://www.mysql.com/).

MySQL 5.1 04/06/2010 MYSQLD_MULTI(1)