Provided by: mysql-server-core-8.0_8.0.37-0ubuntu0.23.10.2_amd64 
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.
Note
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 2.5.9, “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 2.9.5, “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 7.8, “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 command:
mysqld_multi --example
mysqld_multi searches for option files as follows:
• With --no-defaults, no option files are read.
┌────────────────────┬───────────────┐
│Command-Line Format │ --no-defaults │
├────────────────────┼───────────────┤
│Type │ Boolean │
├────────────────────┼───────────────┤
│Default Value │ false │
└────────────────────┴───────────────┘
• With --defaults-file=file_name, only the named file is read.
┌────────────────────┬──────────────────────────┐
│Command-Line Format │ --defaults-file=filename │
├────────────────────┼──────────────────────────┤
│Type │ File name │
├────────────────────┼──────────────────────────┤
│Default Value │ [none] │
└────────────────────┴──────────────────────────┘
• 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.)
┌────────────────────┬────────────────────────────────┐
│Command-Line Format │ --defaults-extra-file=filename │
├────────────────────┼────────────────────────────────┤
│Type │ File name │
├────────────────────┼────────────────────────────────┤
│Default Value │ [none] │
└────────────────────┴────────────────────────────────┘
For additional information about these and other option-file options, see Section 6.2.2.3,
“Command-Line Options that Affect Option-File Handling”.
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.
• --help
┌────────────────────┬─────────┐
│Command-Line Format │ --help │
├────────────────────┼─────────┤
│Type │ Boolean │
├────────────────────┼─────────┤
│Default Value │ false │
└────────────────────┴─────────┘
Display a help message and exit.
• --example
┌────────────────────┬───────────┐
│Command-Line Format │ --example │
├────────────────────┼───────────┤
│Type │ Boolean │
├────────────────────┼───────────┤
│Default Value │ false │
└────────────────────┴───────────┘
Display a sample option file.
• --log=file_name
┌────────────────────┬───────────────────────────┐
│Command-Line Format │ --log=path │
├────────────────────┼───────────────────────────┤
│Type │ File name │
├────────────────────┼───────────────────────────┤
│Default Value │ /var/log/mysqld_multi.log │
└────────────────────┴───────────────────────────┘
Specify the name of the log file. If the file exists, log output is appended to it.
• --mysqladmin=prog_name
┌────────────────────┬───────────────────┐
│Command-Line Format │ --mysqladmin=file │
├────────────────────┼───────────────────┤
│Type │ File name │
├────────────────────┼───────────────────┤
│Default Value │ [none] │
└────────────────────┴───────────────────┘
The mysqladmin binary to be used to stop servers.
• --mysqld=prog_name
┌────────────────────┬───────────────┐
│Command-Line Format │ --mysqld=file │
├────────────────────┼───────────────┤
│Type │ File name │
├────────────────────┼───────────────┤
│Default Value │ [none] │
└────────────────────┴───────────────┘
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
┌────────────────────┬──────────┐
│Command-Line Format │ --no-log │
├────────────────────┼──────────┤
│Type │ Boolean │
├────────────────────┼──────────┤
│Default Value │ false │
└────────────────────┴──────────┘
Print log information to stdout rather than to the log file. By default, output goes
to the log file.
• --password=password
┌────────────────────┬───────────────────┐
│Command-Line Format │ --password=string │
├────────────────────┼───────────────────┤
│Type │ String │
├────────────────────┼───────────────────┤
│Default Value │ [none] │
└────────────────────┴───────────────────┘
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
┌────────────────────┬──────────┐
│Command-Line Format │ --silent │
├────────────────────┼──────────┤
│Type │ Boolean │
├────────────────────┼──────────┤
│Default Value │ false │
└────────────────────┴──────────┘
Silent mode; disable warnings.
• --tcp-ip
┌────────────────────┬──────────┐
│Command-Line Format │ --tcp-ip │
├────────────────────┼──────────┤
│Type │ Boolean │
├────────────────────┼──────────┤
│Default Value │ false │
└────────────────────┴──────────┘
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.
• --user=user_name
┌────────────────────┬─────────────┐
│Command-Line Format │ --user=name │
├────────────────────┼─────────────┤
│Type │ String │
├────────────────────┼─────────────┤
│Default Value │ root │
└────────────────────┴─────────────┘
The user name of the MySQL account to use when invoking mysqladmin.
• --verbose
┌────────────────────┬───────────┐
│Command-Line Format │ --verbose │
├────────────────────┼───────────┤
│Type │ Boolean │
├────────────────────┼───────────┤
│Default Value │ false │
└────────────────────┴───────────┘
Be more verbose.
• --version
┌────────────────────┬───────────┐
│Command-Line Format │ --version │
├────────────────────┼───────────┤
│Type │ Boolean │
├────────────────────┼───────────┤
│Default Value │ false │
└────────────────────┴───────────┘
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 7.8, “Running Multiple MySQL Instances
on One 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 8.1.5, “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:
$> 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 8.2, “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.
• 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.)
• 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.
• 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_multi]
mysqld = /usr/local/mysql/bin/mysqld_safe
mysqladmin = /usr/local/mysql/bin/mysqladmin
user = multi_admin
password = my_password
[mysqld2]
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
[mysqld3]
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
[mysqld4]
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
[mysqld6]
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 6.2.2.2, “Using Option Files”.
COPYRIGHT
Copyright © 1997, 2024, Oracle and/or its affiliates.
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 License for more details.
You should have received a copy of the GNU General Public License along with the program;
if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301 USA or see http://www.gnu.org/licenses/.
SEE ALSO
For more information, please refer to the MySQL Reference Manual, which may already be
installed locally and which is also available online at http://dev.mysql.com/doc/.
AUTHOR
Oracle Corporation (http://dev.mysql.com/).